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This class should provide a default constructor (a public constructor with no arguments) in android manifest

Hi I m getting this error again and again.
Process: pandaboo.run.carromking, PID: 30965
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{pandaboo.run.carromking/pandaboo.run.carromking.MainActivity}: java.lang.InstantiationException: java.lang.Class<pandaboo.run.carromking.MainActivity> has no zero argument constructor
the android manifest is as follow:
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:fullBackupContent="#xml/backup_descriptor"
tools:ignore="AllowBackup">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
there is no error in build but there is a red underline in the manifest under the .MainActivity with error:
This class should provide a default constructor (a public constructor with no arguments) (`pandaboo.run.carromking.MainActivity`)
pls help.
sure the MainActivity is as follow:
public class MainActivity extends Activity {
#SuppressLint("StaticFieldLeak")
static Context context;
public final ThreadLocal<Discovery> disc;
{
disc = new ThreadLocal<Discovery>() {
#Override
protected Discovery initialValue() {
return new Discovery(Discovery.DiscoveryType.MDNS);
}
};
}
public static Publisher gamePublisher;
Subscriber gameSubscriber;
Thread testPublishing;
RenderThread renderThread;
private final Node node;
public MainActivity(Node node) {
this.node = node;
}
public class TestPublishing extends Application implements Runnable {
#Override
public void run() {
while (gamePublisher != null) {
Log.v("CarromGame: umundo", "run");
//gamePublisher.send(message.getBytes());
try {
Thread.sleep(1000);
Log.v("CarromGame:", "sleep");
} catch (InterruptedException e) {
Log.v("CarromGame: exception", "in run");
e.printStackTrace();
}
pandaboo.run.carromking.MainActivity.this.runOnUiThread(() -> {
//tv.setText(tv.getText() + "o");
Log.v("CarromGame: umundo", "context view o");
//contentView = true;
renderThread = new RenderThread(new pandaboo.run.carromking.MainActivity.displayComponents().getHolder(), new MainGamePanel(pandaboo.run.carromking.MainActivity.this));
renderThread.start();
});
}
}
}
public class TestReceiver extends Receiver {
byte[] msgb;
String type = null;
public void receive(Message msg) {
msgb = msg.getData();
type = msg.getMeta("CLASS");
Log.v("CarromGame:umundo value", "TYPE = " + type);
for (String key : msg.getMeta().keySet()) {
Log.v("CarromGame: umundo", key + ": " + msg.getMeta(key) + " value for class" + msg.getMeta("CLASS"));
}
pandaboo.run.carromking.MainActivity.this.runOnUiThread(() -> {
//tv.setText(tv.getText() + "i");
Log.v("CarromGame: umundo", "context view i before");
ObjectInputStream is = null;
if ((type != null) && (!type.equals(""))) {
try {
type = null;
ByteArrayInputStream in = new ByteArrayInputStream(msgb);
is = new ObjectInputStream(in);
is.readObject();
Log.v("CarromGame: umundo", "inside try block " + is.toString());
} catch (Exception e) {
e.printStackTrace();
}
assert is != null;
Log.v("CarromGame: umundo", "context view i after" + is.toString());
renderThread = new RenderThread(new pandaboo.run.carromking.MainActivity.displayComponents().getHolder(), new MainGamePanel(pandaboo.run.carromking.MainActivity.this));
renderThread.start();
}
});
}
}
public class displayComponents extends SurfaceView implements SurfaceHolder.Callback {
public displayComponents() {
super(getApplicationContext());
this.getHolder().addCallback(this);
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
renderThread.running = true;
renderThread.start();
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
while (true) {
try {
renderThread.join();
break;
} catch (InterruptedException ignored) {
}
}
}
}
//Called when activity is created for the first time
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
WifiManager wifi = (WifiManager) getApplicationContext().getSystemService(Context.WIFI_SERVICE);
// To check if there is any active Wifi connection
if (!wifi.isWifiEnabled()) {
startActivity(new Intent(Settings.ACTION_WIFI_SETTINGS));
}
//Allow the application to receive Wifi Multicast packets.
WifiManager.MulticastLock mcLock = wifi.createMulticastLock("gameLock");
mcLock.acquire();
System.loadLibrary("umundoNativeJava");
Objects.requireNonNull(disc.get()).add(node);
Log.v("CarromGame:", "on create");
gamePublisher = new Publisher("Carrom"); //Carrom: channel Name
node.addPublisher(gamePublisher);
//gamePublisher.send();
gameSubscriber = new Subscriber("Carrom", new pandaboo.run.carromking.MainActivity.TestReceiver());
node.addSubscriber(gameSubscriber);
testPublishing = new Thread(new pandaboo.run.carromking.MainActivity.TestPublishing());
//contentView();
testPublishing.start();
Log.v("CarromGame: umundo", "inside context view");
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
//setTitle(title);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
MainGamePanel.PANEL_HEIGHT = this.getWindowManager().getDefaultDisplay().getHeight();
MainGamePanel.PANEL_WIDTH = this.getWindowManager().getDefaultDisplay().getWidth();
setContentView(new MainGamePanel(this));
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_carrom_game_umundo, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
return super.onOptionsItemSelected(item);
}
}

You cannot do this:
public MainActivity(Node node) {
this.node = node;
}
Do not declare any constructors for an Activity. Only the Android framework can instantiate an Activity and you cannot define any additional constructors.

How to Call my Fragment's TextViews and Button from my Activity?

To start with, I'm still new to Android development, I've asked similar questions here before How to make my Fragment make use of my Activity Data? and How to send data from Activity to Fragment?(Android)
But it seems that most people did not quite understand what I mean, so let me explain better.
Suppose I have a TextView:
<TextView
android:id="#+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:text="#string/current"
android:textColor="#FF3D19"
android:textSize="24sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.498"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
and a Button:
<Button
android:id="#+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="14dp"
android:layout_marginTop="92dp"
android:shadowColor="#FFFFFF"
android:text="Click"
android:textColor="#FF5722"
app:layout_constraintStart_toStartOf="#+id/imageView3"
app:layout_constraintTop_toTopOf="#+id/imageView3" />
in my FirstFragment layout.xml, then i want to call them from my MainActivity i.e current_temp = findViewById(R.id.textView10); to get data i.e current_temp.setText(getString(R.string.blank, response.body().getCurrent().getTemp() + " ℃")); from a weather API and findViewById(R.id.button2).setOnClickListener(new View.OnClickListener() {.
Android Studio will not allow you to just use them like that, so i get this error:
java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.view.View.setOnClickListener(android.view.View$OnClickListener)'
on a null object reference
whenever I run the app. I don't get any other error before running, so the reason is that I've not instantiated any method or maybe callback or interface that will tell the Activity to make use of my fragment's TextViews and Button. So that's what I've been stuck with for days trying to fix, but most people just misunderstood me and started suggesting I should learn ViewModel or LiveData. I watched several tutorials on ViewModel including Codinginflow, they never talked about linking activity to fragment TextViews, they only made a fragment send data to another fragment which is not what I want.
My request is similar to this Android: Can't update textview in Fragment from Activity. NullPointerException tried and failed, So I need step by step procedures on how to apply it.
Full Code:
HomeActivity
public class HomeActivity extends AppCompatActivity {
public static String BaseUrl = "http://api.openweathermap.org/";
public static String AppId = "";
public static String lat = "9.0574";
public static String lon = "7.4898";
// User Timezone name, current time, current temperature, current condition, sunrise, sunset, temperature, pressure, humidity, wind_speed, visibility, UV Index
TextView time_zone, time_field, current_temp, current_output, rise_time, set_time, temp_out, Press_out, Humid_out, Ws_out, Visi_out, UV_out;
ConstraintLayout constraintLayout;
public static int count = 0;
int[] drawable = new int[]{R.drawable.dubai, R.drawable.central_bank_of_nigeria, R.drawable.eiffel_tower, R.drawable.hong_kong, R.drawable.statue_of_liberty};
Timer _t;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
time_zone = findViewById(R.id.textView9);
time_field = findViewById(R.id.textView4);
current_temp = findViewById(R.id.textView10);
current_output = findViewById(R.id.textView11);
rise_time = findViewById(R.id.textView25);
set_time = findViewById(R.id.textView26);
temp_out = findViewById(R.id.textView28);
Press_out = findViewById(R.id.textView29);
Humid_out = findViewById(R.id.textView30);
Ws_out = findViewById(R.id.textView33);
Visi_out = findViewById(R.id.textView34);
UV_out = findViewById(R.id.textView35);
BottomNavigationView bottomNavigationView = findViewById(R.id.bottomNavigationView);
NavController navController = Navigation.findNavController(this, R.id.fragment);
NavigationUI.setupWithNavController(bottomNavigationView, navController);
findViewById(R.id.button2).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
getCurrentData();
constraintLayout = findViewById(R.id.layout);
constraintLayout.setBackgroundResource(R.drawable.dubai);
_t = new Timer();
_t.scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
runOnUiThread(new Runnable() { // run on ui thread
#Override
public void run() {
if (count < drawable.length) {
constraintLayout.setBackgroundResource(drawable[count]);
count = (count + 1) % drawable.length;
}
}
});
}
}, 5000, 5000);
}
void getCurrentData() {
Retrofit retrofit = new Retrofit.Builder().baseUrl(BaseUrl).addConverterFactory(GsonConverterFactory.create()).build();
WeatherService service = retrofit.create(WeatherService.class);
Call<WeatherResponse> call = service.getCurrentWeatherData(lat, lon, AppId);
call.enqueue(new Callback<WeatherResponse>() {
#Override
public void onResponse(#NonNull Call<WeatherResponse> call, #NonNull Response<WeatherResponse> response) {
if (response.code() == 200) {
WeatherResponse weatherResponse = response.body();
assert weatherResponse != null;
assert response.body() != null;
time_zone.setText(response.body().getTimezone());
time_field.setText(response.body().getCurrent().getDt());
current_temp.setText(getString(R.string.blank, response.body().getCurrent().getTemp() + " ℃"));
current_output.setText(response.body().getCurrent().getWeather().get(0).getDescription());
rise_time.setText(getString(R.string.blank, response.body().getCurrent().getSunrise() + " AM"));
set_time.setText(getString(R.string.blank, response.body().getCurrent().getSunset() + " PM"));
temp_out.setText(getString(R.string.blank, response.body().getCurrent().getTemp() + " ℃"));
Press_out.setText(getString(R.string.blank, response.body().getCurrent().getPressure() + " hpa"));
Humid_out.setText(getString(R.string.blank, response.body().getCurrent().getHumidity() + " %"));
Ws_out.setText(getString(R.string.blank, response.body().getCurrent().getWindSpeed() + " Km/h"));
Visi_out.setText(getString(R.string.blank, response.body().getCurrent().getVisibility() + " m"));
}
}
#Override
public void onFailure(#NonNull Call<WeatherResponse> call, #NonNull Throwable t) {
}
});
}
});
}
}
FirstFragment
public class FirstFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
public FirstFragment() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment SecondFragment.
*/
// TODO: Rename and change types and number of parameters
public static FirstFragment newInstance(String param1, String param2) {
FirstFragment fragment = new FirstFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_first, container, false);
}
}
Taking the whole functionality to Fragment won't work too, because retrofit can only be called from Activity. But if you have any solid suggestions, I'll appreciate it.

I suggest you two ways can update data to Text View of Fragment from Activity.
1. Call method update Text View of fragment from Activity (simple way)
Create a method updateData()in fragment class to update data to Text View.
You declare a fragment parameter in activity class and assign to this parameter when add fragment to activity.
When you receive data from api in activity, call fragment.updateData()
fragment_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/temp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:text="TextView"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/hud"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:text="TextView"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/temp" />
<Button
android:id="#+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
home_activity.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<FrameLayout
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
FirstFragment.kt
class FirstFragment : Fragment(R.layout.fragment_layout) {
private lateinit var temp: TextView
private lateinit var hud: TextView
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
temp = view.findViewById(R.id.temp)
hud = view.findViewById(R.id.hud)
}
fun setDataToView(data: WeatherResponse) {
temp.text = data.temp
hud.text = data.hud
}
}
HomeActivity.kt
class HomeActivity: AppCompatActivity() {
private val fragment = FirstFragment()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.home_activity)
addFragment()
fragment.view?.findViewById<Button>(R.id.button2)?.setOnClickListener {
getCurrentData()
}
}
private fun addFragment(){
val fm = supportFragmentManager
fm.beginTransaction().replace(R.id.container, fragment, "FirstFragment").commit()
}
private fun getCurrentData(){
//Your retrofit code in here. I only show code in onResponse()
//.....
#Override
public void onResponse(#NonNull Call<WeatherResponse> call, #NonNull Response<WeatherResponse> response) {
if (response.code() == 200) {
fragment.setDataToView(response)
}
}
//....
}
}
2. Using ViewModel
Create a SharedViewModel class with a livedata parameter.
In activity, on onCreate() you create a SharedViewModel paramerter like below:
SharedViewModel viewModel = new SharedViewModel(this).get(SharedViewModel .class);
In fragment, on onActivityCreated() you create a SharedViewModel paramerter like below:
SharedViewModel viewModel = new SharedViewModel(requireActivity()).get(SharedViewModel .class);
Finally, you have same ViewModel instance in activity and fragment because both using activity context. When you receive data from api, update your livedata parameter in activity, fragment also receives livedata parameter onChanged event and then you can update Text View.

There are many ways to achieve what you are tying to do, I will be using RxJava.
Add RxJava in your project:
implementation 'io.reactivex.rxjava3:rxandroid:3.0.0'
Create a POJO class to hold your data which then later can be transferred using RxJava bus
public class WeatherReport {
private String time_zone;
private String time_field;
private String current_temp;
private String current_output;
private String rise_time;
private String set_time;
private String temp_out;
private String Press_out;
private String Humid_out;
private String Ws_out;
private String Visi_out;
public String getCurrent_output() {
return current_output;
}
public String getCurrent_temp() {
return current_temp;
}
public String getHumid_out() {
return Humid_out;
}
public String getPress_out() {
return Press_out;
}
public String getRise_time() {
return rise_time;
}
public String getSet_time() {
return set_time;
}
public String getTemp_out() {
return temp_out;
}
public String getTime_field() {
return time_field;
}
public String getTime_zone() {
return time_zone;
}
public String getVisi_out() {
return Visi_out;
}
public String getWs_out() {
return Ws_out;
}
public void setCurrent_output(String current_output) {
this.current_output = current_output;
}
public void setCurrent_temp(String current_temp) {
this.current_temp = current_temp;
}
public void setHumid_out(String humid_out) {
Humid_out = humid_out;
}
public void setPress_out(String press_out) {
Press_out = press_out;
}
public void setRise_time(String rise_time) {
this.rise_time = rise_time;
}
public void setSet_time(String set_time) {
this.set_time = set_time;
}
public void setTemp_out(String temp_out) {
this.temp_out = temp_out;
}
public void setTime_field(String time_field) {
this.time_field = time_field;
}
public void setTime_zone(String time_zone) {
this.time_zone = time_zone;
}
public void setVisi_out(String visi_out) {
Visi_out = visi_out;
}
public void setWs_out(String ws_out) {
Ws_out = ws_out;
}
}
Create a RxJava bus
import io.reactivex.rxjava3.subjects.BehaviorSubject;
public class RxJavaBus {
private static final BehaviorSubject<WeatherReport> behaviorSubject
= BehaviorSubject.create();
public static BehaviorSubject<WeatherReport> getSubject() {
return behaviorSubject;
}
}
Now from your activity(or from wherever you want to transfer data) use RxBus like this:
WeatherReport weatherReport = new WeatherReport();
weatherReport.setCurrent_output("Some DATA");
weatherReport.setCurrent_temp("Some DATA");
weatherReport.setHumid_out("Some DATA");
weatherReport.setPress_out("Some DATA");
weatherReport.setRise_time("Some DATA");
weatherReport.setSet_time("Some DATA");
weatherReport.setTime_field("Some DATA");
weatherReport.setVisi_out("Some DATA");
weatherReport.setTemp_out("Some DATA");
weatherReport.setWs_out("Some DATA");
weatherReport.setTime_zone("some DATA");
RxJavaBus.getSubject().onNext(weatherReport);
Now you receive your data in your fragment (or wherever you want) like this:
RxJavaBus.getSubject().subscribe(weatherReportFromActivity -> {
weatherReportFromActivity.getCurrent_output();
weatherReportFromActivity.getCurrent_temp();
weatherReportFromActivity.getHumid_out();
weatherReportFromActivity.getPress_out();
weatherReportFromActivity.getRise_time();
weatherReportFromActivity.getSet_time();
weatherReportFromActivity.getWs_out();
weatherReportFromActivity.getTime_zone();
weatherReportFromActivity.getVisi_out();
weatherReportFromActivity.getTime_field();
weatherReportFromActivity.getTemp_out();
});

You're getting a NullPointerException because findViewById(R.id.button2) returns null.
You need to use the fragment's view as the root. The activity.findViewById(...) call uses the activity's view as the root - it's searching activity_home.xml, which doesn't have button2. You can access the fragment's version with fragment.getView().findViewById(R.id._), BUT:
You need to make sure that the fragment has at finished its onCreateView() step in the life cycle. So it has to be launched and inflated. Otherwise, again, the button doesn't exist.
You can make sure your setup is called at the right time and with the view by making it a callback in the fragment life cycle.
//This class can be anywhere - it can be global, private inner, anonymous
class SetupCallback extends FragmentLifeCycleCallback {
#Override
void onFragmentViewCreated(FragmentManager fm, Fragment f, View v, Bundle savedInstanceState) {
ButtonView button = v.findViewById(R.id.button2);
if(button != null) { //This gets called for all fragments so check for null
button.setOnClickListener(new OnClickListener {...});
}
//Repeat for any other elements in the view e.g.
TextView someText = v.findViewById(R.id.someTextView);
someText.setText(R.string.message);
}
}
//In the activity setup - I usually put in onCreate()
SupportFragmentManager.supportFragmentManager = getSupportFragmentManager();
supportFragmentManager.registerFragmentLifecycleCallbacks(new SetupCallback());
//anonymous version:
//supportFragmentManager.registerFragmentLifecycleCallbacks(new FragmentLifecycleCallback() { /*contents of class*/ });
Alternatively you could possibly initialise the Retrofit and Weather service in the Activity, pass them in to the fragment with the constructor or a bundle, then use them to setup the onClickListener in onCreateView().
The RxJava and SharedView approaches are alternatives to having a listener stuck on all the fragment life cycle calls, vs having alternative architectures which make the fragment more reactive.
This needs the androidx.lifecycle.common dependency. If you're using gradle that would be:
dependencies {
implementation 'androidx.lifecycle:lifecycle-common:2.3.0-rc1'
}

Create a class to get retrofit client like below
class RetrofitClient {
private Retrofit retrofit;
private String BASE_URL = "";
public ServiceAPI getRetrofitInstance() {
if (retrofit == null) {
retrofit = new Retrofit.Builder()
.baseUrl(BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.build();
}
return retrofit.create(WeatherService.class);
}
Now you can call apis inside fragment like this
WeatherService service = RetrofitClient().getRetrofitInstance()
void getCurrentData() {
Call<WeatherResponse> call = service.getCurrentWeatherData(lat, lon, AppId);
call.enqueue(new Callback<WeatherResponse>() {
#Override
public void onResponse(#NonNull Call<WeatherResponse> call, #NonNull Response<WeatherResponse> response) {
if (response.code() == 200) {
WeatherResponse weatherResponse = response.body();
assert weatherResponse != null;
assert response.body() != null;
time_zone.setText(response.body().getTimezone());
time_field.setText(response.body().getCurrent().getDt());
current_temp.setText(getString(R.string.blank, response.body().getCurrent().getTemp() + " ℃"));
current_output.setText(response.body().getCurrent().getWeather().get(0).getDescription());
rise_time.setText(getString(R.string.blank, response.body().getCurrent().getSunrise() + " AM"));
set_time.setText(getString(R.string.blank, response.body().getCurrent().getSunset() + " PM"));
temp_out.setText(getString(R.string.blank, response.body().getCurrent().getTemp() + " ℃"));
Press_out.setText(getString(R.string.blank, response.body().getCurrent().getPressure() + " hpa"));
Humid_out.setText(getString(R.string.blank, response.body().getCurrent().getHumidity() + " %"));
Ws_out.setText(getString(R.string.blank, response.body().getCurrent().getWindSpeed() + " Km/h"));
Visi_out.setText(getString(R.string.blank, response.body().getCurrent().getVisibility() + " m"));
}
}
#Override
public void onFailure(#NonNull Call<WeatherResponse> call, #NonNull Throwable t) {
}
});
}
});
}

Set the data you want to update in the bundle set fragment arguments and call the newInstance then update your views accordingly.
From Activity
FirstFragment.newInstance("yourData","yourData");
In your Fragment
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}

Android ConnectivityManager NetworkCallback crash

I'm new in Android world (as user but also as developer) and my Android App crash when execute myWebView.loadUrl("https://www.google.com"), but I don't understand why...
The goal is monitoring internet connection while the app is running:
If the connection is lost -> loads the error html in the web view
If the connection returns active -> reload the web view
Here's my app code:
Manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.dedalos.amb">
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<application
android:name=".MyApplication"
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity android:name=".SplashScreen" android:theme="#style/SplashTheme">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
MainActivity
public class MainActivity extends AppCompatActivity {
// WEB VIEW
WebView myWebView = null;
// NETWORK MONITORING
Boolean isInternetConnected = false;
ConnectivityManager.NetworkCallback networkCallback = null;
ConnectivityManager connectivityManager = null;
//////////////////// OVERRIDE ////////////////////
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
hideSystemUI();
SharedPreferences prefs = getPreferences(MODE_PRIVATE);
if (getToken().equals("")) {
String uniqueID = UUID.randomUUID().toString();
SharedPreferences.Editor editor = prefs.edit();
editor.putString("token", uniqueID);
editor.commit();
}
creaWebView();
configuraWebView();
initNetworkCallback();
}
#Override
public void onResume() {
super.onResume();
if (myWebView == null) {
creaWebView();
configuraWebView();
}
if (networkCallback == null || connectivityManager == null)
initNetworkCallback();
isInternetConnected = (new ConnectionDetector(this).isConnectingToInternet());
startNetworkMonitoring();
if (isInternetConnected) {
caricaWebView();
}
else {
MyWebViewClient.loadError(myWebView);
}
}
#Override
public void onPause() {
super.onPause();
stopNetworkMonitoring();
}
private void creaWebView() {
if (myWebView == null) {
myWebView = (WebView) findViewById(R.id.ambWebViewLayout);
}
}
private void configuraWebView() {
WebSettings webSettings = myWebView.getSettings();
webSettings.setJavaScriptEnabled(true);
myWebView.setWebViewClient(new MyWebViewClient());
}
private void caricaWebView() {
if (myWebView == null) {
creaWebView();
configuraWebView();
}
myWebView.loadUrl("https://www.google.com");
}
private void initNetworkCallback() {
networkCallback = new ConnectivityManager.NetworkCallback() {
#Override
public void onAvailable(Network network) {
if (!isInternetConnected) {
isInternetConnected = true;
caricaWebView();
}
}
#Override
public void onLost(Network network) {
if (isInternetConnected) {
isInternetConnected = false;
MyWebViewClient.loadError(myWebView);
}
}
};
connectivityManager = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
}
private void startNetworkMonitoring() {
if (networkCallback == null)
initNetworkCallback();
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
connectivityManager.registerDefaultNetworkCallback(networkCallback);
}
else {
NetworkRequest request = new NetworkRequest.Builder().addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET).build();
connectivityManager.registerNetworkCallback(request, networkCallback);
}
}
private void stopNetworkMonitoring() {
connectivityManager.unregisterNetworkCallback(networkCallback);
}
private String getToken() {
return getPreferences(MODE_PRIVATE).getString("token", "");
}
private void hideSystemUI() {
View decorView = getWindow().getDecorView();
decorView.setSystemUiVisibility(
View.SYSTEM_UI_FLAG_IMMERSIVE
// Set the content to appear under the system bars so that the
// content doesn't resize when the system bars hide and show.
| View.SYSTEM_UI_FLAG_LAYOUT_STABLE
| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
// Hide the nav bar and status bar
| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);
}
}
MyWebViewClient
public class MyWebViewClient extends WebViewClient {
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
if (url.startsWith("https://www.google.com")) {
view.getContext().startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(url)));
return true;
}
else {
return false;
}
}
#Override
public void onReceivedError(WebView view, WebResourceRequest request, WebResourceError error) {
super.onReceivedError(view, request, error);
if (error.getErrorCode() == -2) {
loadError(view);
}
else {
// TODO
}
}
public static void loadError(WebView view) {
String html = "<!DOCTYPE HTML>\n" +
"<html>\n" +
"<head>\n" +
"<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\" />\n" +
"<title>APP</title>\n" +
"</head>\n" +
"<body style=\"background:#e11020;font-family:Arial,Helvetica;\">\n" +
"<h1 style=\"color:rgba(255,255,255,0.9);text-align:center;padding:120px 20px 20px 20px;font-size:30px;\">No Internet connection</h1>\n" +
"</body>\n" +
"</html>";
view.loadDataWithBaseURL(null, html, "text/html", "UTF-8", null);
}
}
ConnectionDetector
public class ConnectionDetector {
private Context mContext;
public ConnectionDetector(Context context) {
this.mContext = context;
}
/**
* Checking for all possible internet providers
* **/
public boolean isConnectingToInternet() {
ConnectivityManager connectivityManager = (ConnectivityManager) mContext.getSystemService(Context.CONNECTIVITY_SERVICE);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
Network[] networks = connectivityManager.getAllNetworks();
NetworkInfo networkInfo;
for (Network mNetwork : networks) {
networkInfo = connectivityManager.getNetworkInfo(mNetwork);
if (networkInfo.getState().equals(NetworkInfo.State.CONNECTED)) {
return true;
}
}
}
else {
if (connectivityManager != null) {
//noinspection deprecation
NetworkInfo[] info = connectivityManager.getAllNetworkInfo();
if (info != null) {
for (NetworkInfo anInfo : info) {
if (anInfo.getState() == NetworkInfo.State.CONNECTED) {
return true;
}
}
}
}
}
return false;
}
}
Thanks in advance

According to this you need to call all view related methods on UI thread. Just load the url on UI thread like this:
myWebView.post(new Runnable() {
#Override
public void run() {
myWebView.loadUrl("https://www.google.com");
}
});
You also need to load your error html in the same way, like:
view.post(new Runnable() {
#Override
public void run() {
String html = "<!DOCTYPE HTML>\n" +
"<html>\n" +
"<head>\n" +
"<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\" />\n" +
"<title>APP</title>\n" +
"</head>\n" +
"<body style=\"background:#e11020;font-family:Arial,Helvetica;\">\n" +
"<h1 style=\"color:rgba(255,255,255,0.9);text-align:center;padding:120px 20px 20px 20px;font-size:30px;\">No Internet connection</h1>\n" +
"</body>\n" +
"</html>";
view.loadDataWithBaseURL(null, html, "text/html", "UTF-8", null);
}
});

If you get Only the original thread that created a view hierarchy can touch its views error in your Logcat, use this.

Android : UI and data not survive when screen rotation in MVVM pattern

I try to implement MVVM by Mindorks to show data from here :(https://api.themoviedb.org/3/movie/384018?api_key=67bc513a7a353631119fdffe5f7377a8&language=en-US) in my Activity. I try using databinding for update UI, everything is going well untill I try to rotate my screen, I see from my logcat the data is always reload and my ImageView is always refresh, this is my Activity:
public class DetailActivity extends BaseActivity<ActivityDetailBinding, DetailViewModel> implements DetailNavigator {
#Inject
ViewModelProviderFactory factory;
private DetailViewModel detailViewModel;
public static final String INTENT_ID = "id_intent";
public static final String INTENT_FLAG = "id_flag";
private ActivityDetailBinding mActivityDetailBinding;
public static Intent newIntent(Context context) {
return new Intent(context, DetailActivity.class);
}
#Override
public int getBindingVariable() {
return BR.viewModel;
}
#Override
public int getLayoutId() {
return R.layout.activity_detail;
}
#Override
public DetailViewModel getViewModel() {
detailViewModel = ViewModelProviders.of(this, factory).get(DetailViewModel.class);
return detailViewModel;
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
detailViewModel.setNavigator(this);
mActivityDetailBinding = getViewDataBinding();
initView();
initData(savedInstanceState);
}
private void initData(Bundle savedInstanceState) {
Bundle extras = getIntent().getExtras();
if (extras != null) {
int id = extras.getInt(INTENT_ID, 0);
int flag = extras.getInt(INTENT_FLAG, 0);
detailViewModel.fetchDetail(id, flag);
}
}
private void initView() {
if (getSupportActionBar() != null) {
getSupportActionBar().hide();
}
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
}
#Override
public void ShowProgressDialog(Boolean loading) {
if (loading) {
showLoading();
} else {
hideLoading();
}
}
}
and my BaseActivity like this :
public abstract class BaseActivity<T extends ViewDataBinding, V extends BaseViewModel> extends AppCompatActivity
implements BaseFragment.Callback {
// TODO
// this can probably depend on isLoading variable of BaseViewModel,
// since its going to be common for all the activities
private ProgressDialog mProgressDialog;
private T mViewDataBinding;
private V mViewModel;
/**
* Override for set binding variable
*
* #return variable id
*/
public abstract int getBindingVariable();
/**
* #return layout resource id
*/
public abstract
#LayoutRes
int getLayoutId();
/**
* Override for set view model
*
* #return view model instance
*/
public abstract V getViewModel();
#Override
public void onFragmentAttached() {
}
#Override
public void onFragmentDetached(String tag) {
}
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
performDependencyInjection();
super.onCreate(savedInstanceState);
performDataBinding();
}
public T getViewDataBinding() {
return mViewDataBinding;
}
#TargetApi(Build.VERSION_CODES.M)
public boolean hasPermission(String permission) {
return Build.VERSION.SDK_INT < Build.VERSION_CODES.M ||
checkSelfPermission(permission) == PackageManager.PERMISSION_GRANTED;
}
public void hideKeyboard() {
View view = this.getCurrentFocus();
if (view != null) {
InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
if (imm != null) {
imm.hideSoftInputFromWindow(view.getWindowToken(), 0);
}
}
}
public void hideLoading() {
if (mProgressDialog != null && mProgressDialog.isShowing()) {
mProgressDialog.cancel();
}
}
public void showLoading() {
hideLoading();
mProgressDialog = CommonUtils.showLoadingDialog(this);
}
public boolean isNetworkConnected() {
return NetworkUtils.isNetworkConnected(getApplicationContext());
}
public void performDependencyInjection() {
AndroidInjection.inject(this);
}
#TargetApi(Build.VERSION_CODES.M)
public void requestPermissionsSafely(String[] permissions, int requestCode) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
requestPermissions(permissions, requestCode);
}
}
// public void showLoading() {
// hideLoading();
// mProgressDialog = CommonUtils.showLoadingDialog(this);
// }
private void performDataBinding() {
mViewDataBinding = DataBindingUtil.setContentView(this, getLayoutId());
this.mViewModel = mViewModel == null ? getViewModel() : mViewModel;
mViewDataBinding.setVariable(getBindingVariable(), mViewModel);
mViewDataBinding.setLifecycleOwner(this);
mViewDataBinding.executePendingBindings();
}
#Override
protected void onResume() {
super.onResume();
}
#Override
protected void onDestroy() {
super.onDestroy();
}
}
this is my ViewModelFactory class :
#Singleton
public class ViewModelProviderFactory extends ViewModelProvider.NewInstanceFactory {
private final DataManager dataManager;
private final SchedulerProvider schedulerProvider;
#Inject
public ViewModelProviderFactory(DataManager dataManager,
SchedulerProvider schedulerProvider) {
this.dataManager = dataManager;
this.schedulerProvider = schedulerProvider;
}
#Override
public <T extends ViewModel> T create(Class<T> modelClass) {
if (modelClass.isAssignableFrom(DetailViewModel.class)) {
return (T) new DetailViewModel(dataManager,schedulerProvider);
}
throw new IllegalArgumentException("Unknown class name");
}
}
this is my ViewModel class :
public class DetailViewModel extends BaseViewModel<DetailNavigator> {
private final ObservableField<String> originalName = new ObservableField<>();
private final ObservableField<String> releaseDate = new ObservableField<>();
private final ObservableField<String> overview = new ObservableField<>();
private final ObservableField<String> genreMovie = new ObservableField<>();
private final ObservableField<String> posterPath = new ObservableField<>();
private final ObservableField<String> voteAverage = new ObservableField<>();
public DetailViewModel(DataManager dataManager, SchedulerProvider schedulerProvider) {
super(dataManager, schedulerProvider);
}
public void fetchDetail(int id, int flag) {
if (flag == 1) {
getNavigator().ShowProgressDialog(true);
getCompositeDisposable().add(getDataManager()
.getApiHelper().doDetailMovie(id, URLConfig.API_KEY, getDataManager().getLanguage())
.subscribeOn(getSchedulerProvider().io())
.observeOn(getSchedulerProvider().ui())
.subscribe(detailResponse -> {
setUpData(detailResponse);
getNavigator().ShowProgressDialog(false);
// getNavigator().updateView();
}, throwable -> {
getNavigator().ShowProgressDialog(false);
}));
} else if (flag == 2) {
getNavigator().ShowProgressDialog(true);
getCompositeDisposable().add(getDataManager()
.getApiHelper().doDetailTV(id, URLConfig.API_KEY, getDataManager().getLanguage())
.subscribeOn(getSchedulerProvider().io())
.observeOn(getSchedulerProvider().ui())
.subscribe(detailResponse -> {
setUpData(detailResponse);
getNavigator().ShowProgressDialog(false);
}, throwable -> {
getNavigator().ShowProgressDialog(false);
}));
}
}
private void setUpData(DetailResponse detailResponse) {
if (detailResponse.getOriginal_name() != null) {
originalName.set(detailResponse.getOriginal_name());
} else if (detailResponse.getOriginal_title() != null) {
originalName.set(detailResponse.getOriginal_title());
} else {
}
if (detailResponse.getFirst_air_date() != null) {
releaseDate.set(detailResponse.getFirst_air_date());
} else {
releaseDate.set(detailResponse.getRelease_date());
}
if (!detailResponse.getOverview().equals("")) {
overview.set(detailResponse.getOverview());
} else {
overview.set(getNavigator().noDesc());
}
posterPath.set(String.valueOf(detailResponse.getPoster_path()));
voteAverage.set(String.valueOf(detailResponse.getVote_average()));
String genres = "";
for (int i = 0; i < detailResponse.getGenreList().size(); i++) {
genres = genres + detailResponse.getGenreList().get(i).getName();
if (i != detailResponse.getGenreList().size() - 1) {
genres = genres + ", ";
}
}
genreMovie.set(genres);
}
public ObservableField<String> getOriginalName() {
return originalName;
}
public ObservableField<String> getReleaseDate() {
return releaseDate;
}
public ObservableField<String> getOverview() {
return overview;
}
public ObservableField<String> getGenreMovie() {
return genreMovie;
}
public ObservableField<String> getPosterPath() {
return posterPath;
}
public ObservableField<String> getVoteAverage() {
return voteAverage;
}
}
and this is my DetailResponse Class :
public class DetailResponse {
#SerializedName("original_name")
private String original_name ;
#SerializedName("original_title")
private String original_title ;
#SerializedName("release_date")
private String release_date ;
#SerializedName("first_air_date")
private String first_air_date ;
#SerializedName("vote_average")
private Double vote_average ;
#SerializedName("overview")
private String overview ;
#SerializedName("poster_path")
private String poster_path;
#SerializedName("genres")
private List<Genre> genreList;
public String getOriginal_name() {
return original_name;
}
public String getOriginal_title() {
return original_title;
}
public String getRelease_date() {
return release_date;
}
public String getFirst_air_date() {
return first_air_date;
}
public Double getVote_average() {
return vote_average;
}
public String getOverview() {
return overview;
}
public String getPoster_path() {
return poster_path;
}
public List<Genre> getGenreList() {
return genreList;
}
public static class Genre{
#SerializedName("name")
private String name ;
public String getName() {
return name;
}
}
}
and last one, here how I try to get data in my UI using databinding, this is my layout :
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
tools:context=".ui.detail.DetailActivity">
<data>
<import type="android.view.View" />
<variable
name="viewModel"
type="id.dicoding.eriza.moviecatalogue.ui.detail.DetailViewModel" />
</data>
<androidx.core.widget.NestedScrollView
android:id="#+id/nestedScrollView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fillViewport="true">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:animateLayoutChanges="true">
<com.github.florent37.shapeofview.shapes.ArcView
android:id="#+id/shape_header"
android:layout_width="match_parent"
android:layout_height="#dimen/size300dp"
android:alpha="0.7"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:shape_arc_cropDirection="outside"
app:shape_arc_height="#dimen/size30dp"
app:shape_arc_position="bottom">
<com.flaviofaria.kenburnsview.KenBurnsView
android:id="#+id/image_header"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scaleType="centerCrop"
android:src="#drawable/poster_avengerinfinity"
app:imageDetailUrl="#{viewModel.posterPath}"
android:tint="#6F000000" />
</com.github.florent37.shapeofview.shapes.ArcView>
<com.github.florent37.shapeofview.shapes.RoundRectView
android:id="#+id/shape_poster"
android:layout_width="#dimen/size150dp"
android:layout_height="#dimen/size200dp"
android:layout_marginTop="#dimen/margin250dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="#+id/shape_header"
app:shape_roundRect_bottomLeftRadius="#dimen/corner10dp"
app:shape_roundRect_bottomRightRadius="#dimen/corner10dp"
app:shape_roundRect_topLeftRadius="#dimen/corner10dp"
app:shape_roundRect_topRightRadius="#dimen/corner10dp">
<ImageView
android:id="#+id/image_poster"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:contentDescription="#string/hint_poster"
android:scaleType="fitXY"
app:imageDetailUrl="#{viewModel.posterPath}"
android:src="#drawable/poster_avengerinfinity" />
</com.github.florent37.shapeofview.shapes.RoundRectView>
<TextView
android:id="#+id/text_title"
style="#style/FontText.Title.Detail"
android:layout_marginTop="#dimen/margin15dp"
android:textSize="#dimen/font_large_size"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/shape_poster"
android:text="#{viewModel.originalName}"
tools:text="#string/hint_title" />
<TextView
android:id="#+id/text_title_release"
style="#style/FontText"
android:layout_marginTop="#dimen/margin10dp"
android:text="#string/text_release"
app:layout_constraintEnd_toStartOf="#+id/guideline"
android:visibility="#{viewModel.isConnected ? View.VISIBLE : View.GONE}"
app:layout_constraintTop_toBottomOf="#+id/text_title" />
<TextView
android:id="#+id/text_release"
style="#style/FontText"
android:layout_marginStart="#dimen/margin2dp"
android:layout_marginTop="#dimen/margin10dp"
android:text="#{viewModel.releaseDate}"
android:visibility="#{viewModel.isConnected ? View.VISIBLE : View.GONE}"
app:layout_constraintStart_toEndOf="#+id/text_title_release"
app:layout_constraintTop_toBottomOf="#+id/text_title"
tools:text="#string/hint_release" />
<TextView
android:id="#+id/text_genres"
style="#style/FontText.Normal"
android:layout_marginStart="#dimen/margin15dp"
android:layout_marginTop="#dimen/margin10dp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/text_release"
android:text="#{viewModel.genreMovie}"
tools:text="#string/hint_genres" />
<RatingBar
android:id="#+id/rating_bar"
android:layout_width="wrap_content"
android:layout_height="45dp"
android:layout_marginStart="#dimen/margin15dp"
android:layout_marginTop="#dimen/margin5dp"
android:isIndicator="true"
android:numStars="5"
android:rating="3.8"
android:stepSize="0.1"
android:visibility="#{viewModel.isConnected ? View.VISIBLE : View.GONE}"
app:layout_constraintStart_toStartOf="parent"
app:ratingBar="#{viewModel.voteAverage}"
app:layout_constraintTop_toBottomOf="#+id/text_genres" />
<TextView
android:id="#+id/text_rating"
style="#style/FontText.Rating.Orange"
android:layout_marginStart="#dimen/margin5dp"
app:layout_constraintRight_toLeftOf="parent"
app:layout_constraintStart_toEndOf="#+id/rating_bar"
app:layout_constraintTop_toBottomOf="#+id/text_genres"
android:text="#{viewModel.voteAverage}"
tools:text="#string/hit_rating" />
<TextView
android:id="#+id/text_default_rating"
style="#style/FontText.Rating"
android:textStyle="normal"
android:visibility="#{viewModel.isConnected ? View.VISIBLE : View.GONE}"
app:layout_constraintRight_toLeftOf="parent"
app:layout_constraintStart_toEndOf="#+id/text_rating"
app:layout_constraintTop_toBottomOf="#+id/text_genres"
android:text="#string/hint_default_rating" />
<TextView
android:id="#+id/text_desc"
style="#style/FontText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="#dimen/margin15dp"
android:layout_marginTop="#dimen/margin25dp"
android:layout_marginEnd="#dimen/margin15dp"
android:paddingBottom="#dimen/padding100dp"
app:layout_constraintTop_toBottomOf="#+id/rating_bar"
android:text="#{viewModel.overview}"
tools:text="#string/hint_desc" />
<androidx.constraintlayout.widget.Guideline
android:id="#+id/guideline"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_percent="0.5" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.core.widget.NestedScrollView>
</layout>
I think ViewModelshould manages UI that related data in Activity lifecycle, and tt allows to survive configuration changes in the Application, but in my case, the data is survive, but when I check on my logcat the fetchDetail() in DetailViewModel class is always call when screen rotation, and my ImageView is also refresh when I rotate my screen, so I think the viewModel not manage my UI when screen rotation. is there any problem with my code?
hope anybody can help me to show me where is my fault and what I must do. Thank you very much.

Application receiving NFC always pops up new instance in front

I run through the following life-cycle when starting my app through the launcher:
onCreate..., onPostCreate..., onResume..., onNewIntent..., act:android.intent.action.MAIN, mNfcAdapter.disableForegroundDispatch OK.
When I then tap a tag, a new instance of application seems to be launched as I run through the following life-cycle then:
onPause..., onCreate..., onPostCreate..., onResume..., onNewIntent..., act:android.nfc.action.TAG_DISCOVERED, myTag.mId:048a1382bd2384)
Since I try to use the foreground dispatch system to disable recieving NFC events, I expected my app to ignore the NFC tag. So why is my activity recreated instead? Is it because AndroidManifest.xml allows it?
package com.example.pdf.nfcaccess;
import android.annotation.SuppressLint;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.os.Handler;
import android.view.MotionEvent;
import android.view.View;
// PDf import
import android.telephony.TelephonyManager;
import android.content.Intent;
import android.content.Context;
import android.content.IntentFilter;
import android.app.PendingIntent;
import android.nfc.NdefMessage;
import android.nfc.NdefRecord;
import android.nfc.NfcAdapter;
import android.nfc.NfcAdapter.CreateNdefMessageCallback;
import android.nfc.NfcEvent;
import android.widget.TextView;
import android.widget.Toast;
import android.util.Log;
import android.nfc.tech.NfcF;
import android.nfc.Tag;
/**
* An example full-screen activity that shows and hides the system UI (i.e.
* status bar and navigation/system bar) with user interaction.
*/
public class FullscreenActivity extends AppCompatActivity {
/**
* Whether or not the system UI should be auto-hidden after
* {#link #AUTO_HIDE_DELAY_MILLIS} milliseconds.
*/
private static final boolean AUTO_HIDE = true;
/**
* If {#link #AUTO_HIDE} is set, the number of milliseconds to wait after
* user interaction before hiding the system UI.
*/
private static final int AUTO_HIDE_DELAY_MILLIS = 3000;
/**
* Some older devices needs a small delay between UI widget updates
* and a change of the status and navigation bar.
*/
private static final int UI_ANIMATION_DELAY = 300;
private final Handler mHideHandler = new Handler();
private View mContentView;
private final Runnable mHidePart2Runnable = new Runnable() {
#SuppressLint("InlinedApi")
#Override
public void run() {
// Delayed removal of status and navigation bar
// Note that some of these constants are new as of API 16 (Jelly Bean)
// and API 19 (KitKat). It is safe to use them, as they are inlined
// at compile-time and do nothing on earlier devices.
mContentView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LOW_PROFILE
| View.SYSTEM_UI_FLAG_FULLSCREEN
| View.SYSTEM_UI_FLAG_LAYOUT_STABLE
| View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);
}
};
private View mControlsView;
// application
static FullscreenActivity mInstance;
NfcAdapter mNfcAdapter;
Intent mNfcIntent;
PendingIntent mNfcPendingIntent;
IntentFilter mTagIntentFilter;
IntentFilter[] mIntentFiltersArray;
String[][] mTechLists;
TextView mTagContentText;
// log
//java.util.ArrayList<String> mLogItems = new java.util.ArrayList<String>();
java.util.ArrayList<String> mLogItems = new java.util.ArrayList<String>();
android.widget.ArrayAdapter<String> mLogAdapter;
android.widget.ListView mLogList;
/**/
private final Runnable mShowPart2Runnable = new Runnable() {
#Override
public void run() {
// Delayed display of UI elements
ActionBar actionBar = getSupportActionBar();
if (actionBar != null) {
actionBar.show();
}
mControlsView.setVisibility(View.VISIBLE);
}
};
private boolean mVisible;
private final Runnable mHideRunnable = new Runnable() {
#Override
public void run() {
hide();
}
};
/**
* Touch listener to use for in-layout UI controls to delay hiding the
* system UI. This is to prevent the jarring behavior of controls going away
* while interacting with activity UI.
*/
/* Enable NFC
*/
private final View.OnTouchListener mFuncNfcEnable = new View.OnTouchListener() {
#Override
public boolean onTouch(View view, MotionEvent motionEvent) {
if (motionEvent.getAction() == MotionEvent.ACTION_DOWN) {
traceTry("mFuncNfcEnable");
if (mNfcAdapter != null) {
try {
traceTry("mNfcAdapter.enableForegroundDispatch");
mNfcAdapter.enableForegroundDispatch(FullscreenActivity.mInstance, mNfcPendingIntent, mIntentFiltersArray, mTechLists);
traceOk();
}
catch (Throwable t) {
traceFails(t);
}
}
}
return false;
}
};
/* read Intent
*/
private final View.OnTouchListener mFuncNfcRead = new View.OnTouchListener() {
#Override
public boolean onTouch(View view, MotionEvent motionEvent) {
if (mNfcAdapter != null) {
try {
traceTry("onNewIntent");
onNewIntent(getIntent());
traceOk();
}
catch (Throwable t) {
traceFails(t);
}
}
return false;
}
};
/* Disable NFC
*/
private final View.OnTouchListener mFuncNfcDisable = new View.OnTouchListener() {
#Override
public boolean onTouch(View view, MotionEvent motionEvent) {
if (motionEvent.getAction() == MotionEvent.ACTION_DOWN){
traceTry("mFuncNfcDisable");
if (mNfcAdapter != null) {
try {
traceTry("mNfcAdapter.disableForegroundDispatch");
mNfcAdapter.disableForegroundDispatch(FullscreenActivity.mInstance);
traceOk();
}
catch (Throwable t) {
traceFails(t);
}
}
}
return false;
}
};
/* Quit
*/
private final View.OnTouchListener mFuncBtnQuit = new View.OnTouchListener() {
#Override
public boolean onTouch(View view, MotionEvent motionEvent) {
finish();
return false;
}
};
/**/
private void trace(String m) {
Log.d("NFCTags",m);
/*TextView tv = (TextView)findViewById(R.id.logContent_value);
String previous = tv.getText().toString();
tv.setText(previous + "\n" + m);*/
if (mLogAdapter != null) {
mLogItems.add(m);
mLogAdapter.notifyDataSetChanged();
mLogList.setSelection(mLogList.getCount()-1);
}
}
String mMessage = "";
private void traceTry(String m) {
trace(m + "...");
mMessage = m;
}
private void traceOk() {
trace(mMessage + " OK");
mMessage = "";
}
private void traceFails(Throwable t) {
String msg = mMessage + " fails";
if (t != null) {
msg += " exception:" + t.getMessage();
}
trace(msg);
//Toast.makeText(this, msg, Toast.LENGTH_LONG).show();
mMessage = "";
}
/*
*/
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
trace("onCreate...");
// set global unique instance
FullscreenActivity.mInstance = this;
setContentView(R.layout.activity_fullscreen);
// log
mLogItems.add("starts");
mLogAdapter = new android.widget.ArrayAdapter<String>(this, R.layout.support_simple_spinner_dropdown_item, mLogItems);
mLogList = (android.widget.ListView) findViewById(R.id.logList_value);
mLogList.setAdapter(mLogAdapter);
mVisible = true;
mControlsView = findViewById(R.id.fullscreen_content_controls);
mContentView = findViewById(R.id.fullscreen_content);
mTagContentText = (TextView) findViewById(R.id.tagContent_value);
// Set up the user interaction to manually show or hide the system UI.
mContentView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
toggle();
}
});
// Upon interacting with UI controls, delay any scheduled hide()
// operations to prevent the jarring behavior of controls going away
// while interacting with the UI.
findViewById(R.id.nfcRead_btn).setOnTouchListener(mFuncNfcRead);
//findViewById(R.id.nfcDisable_btn).setOnTouchListener(mFuncNfcDisable);
findViewById(R.id.quit_btn).setOnTouchListener(mFuncBtnQuit);
trace("onCreate > before initializing nfc");
TelephonyManager tm = (TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);
trace("ID:" + tm.getDeviceId());
trace("Network Operator Name:" + tm.getNetworkOperatorName());
trace("Sim Operator Name:" + tm.getSimOperatorName());
trace("Sim Serial Number:" + tm.getSimSerialNumber());
trace("Phone Type:" + tm.getPhoneType());
trace("Initial Phone Number:" + tm.getLine1Number());
boolean tryNfc = true;
if (tryNfc) {
try {
mMessage = "NfcAdapter.getDefaultAdapter";
mNfcAdapter = NfcAdapter.getDefaultAdapter(this);
if (mNfcAdapter == null) {
mMessage = "NFC is not available";
traceFails(null);
return;
} else {
traceOk();
}
} catch (Throwable t) {
traceFails(t);
return;
}
// Check if NFC is enabled
try {
mMessage = "test NfcAdapter.isEnabled";
if (!mNfcAdapter.isEnabled()) {
mMessage = "NFC is not enabled. do it manually";
traceFails(null);
return;
} else {
trace("NFC is enabled.");
}
} catch (Throwable t) {
traceFails(t);
return;
}
try {
mMessage = "create new Intent";
mNfcIntent = new Intent(this, getClass());
traceOk();
} catch (Throwable t) {
traceFails(t);
return;
}
try {
mMessage = "mNfcIntent.addFlags, PendingIntent.getActivity";
mNfcIntent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
mNfcPendingIntent = PendingIntent.getActivity(this, 0, mNfcIntent, 0);
traceOk();
} catch (Throwable t) {
traceFails(t);
return;
}
try {
mMessage = "new IntentFilter";
mTagIntentFilter = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
mTagIntentFilter.addCategory(Intent.CATEGORY_DEFAULT);
traceOk();
} catch (Throwable t) {
traceFails(t);
return;
}
try {
mMessage = "addDataType, new IntentFilter[]";
mTagIntentFilter.addDataType("*/*");
//mTagIntentFilter.addDataType("text/plain");
mIntentFiltersArray = new IntentFilter[]{mTagIntentFilter};
traceOk();
} catch (Throwable t) {
traceFails(t);
return;
}
// Setup a tech list for all NfcF tags
try {
mMessage = "new tech list";
//mTechLists = new String[][]{new String[]{NfcF.class.getName()}};
mTechLists = new String[][]{};
traceOk();
} catch (Throwable t) {
traceFails(t);
return;
}
/*
if (mNfcAdapter != null) {
try {
mMessage = "mNfcAdapter.enableForegroundDispatch";
mNfcAdapter.enableForegroundDispatch(FullscreenActivity.mInstance, mNfcPendingIntent, mIntentFiltersArray, mTechLists);
traceOk();
}
catch (Throwable t) {
traceFails(t);
}
}
*/
}
}
#Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
trace("onPostCreate...");
// Trigger the initial hide() shortly after the activity has been
// created, to briefly hint to the user that UI controls
// are available.
//delayedHide(100);
}
private void toggle() {
trace("toggle...");
if (mVisible) {
hide();
} else {
show();
}
}
private void hide() {
trace("hide...");
// Hide UI first
ActionBar actionBar = getSupportActionBar();
if (actionBar != null) {
actionBar.hide();
}
mControlsView.setVisibility(View.GONE);
mVisible = false;
// Schedule a runnable to remove the status and navigation bar after a delay
mHideHandler.removeCallbacks(mShowPart2Runnable);
mHideHandler.postDelayed(mHidePart2Runnable, UI_ANIMATION_DELAY);
}
#SuppressLint("InlinedApi")
private void show() {
// Show the system bar
mContentView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION);
mVisible = true;
// Schedule a runnable to display UI elements after a delay
mHideHandler.removeCallbacks(mHidePart2Runnable);
mHideHandler.postDelayed(mShowPart2Runnable, UI_ANIMATION_DELAY);
}
/**
* Schedules a call to hide() in [delay] milliseconds, canceling any
* previously scheduled calls.
*/
private void delayedHide(int delayMillis) {
mHideHandler.removeCallbacks(mHideRunnable);
mHideHandler.postDelayed(mHideRunnable, delayMillis);
}
/**/
public String intentToText(Intent intent){
String report = "?";
try {
Bundle bundle = intent.getExtras();
if (bundle != null) {
java.util.Set<String> keys = bundle.keySet();
java.util.Iterator<String> it = keys.iterator();
report = "Intent:{";
while (it.hasNext()) {
String key = it.next();
report += "\n[" + key + ":" + bundle.get(key) + "],";
}
report += "}\n";
}
}
catch(Throwable t){
trace("intentToText > " + t.getMessage());
}
return report;
}
/**/
public static String byteArrayToHex(byte[] a) {
StringBuilder sb = new StringBuilder(a.length * 2);
for(byte b: a)
sb.append(String.format("%02x", b & 0xff));
return sb.toString();
}
/**/
#Override
public void onNewIntent(Intent intent) {
super.onNewIntent(intent);
trace("onNewIntent...");
handleIntent(intent);
}
/**/
void handleIntent(Intent intent) {
if (intent == null) return;
String sAction = intent.getAction();
trace("act:" + sAction);
if( (NfcAdapter.ACTION_NDEF_DISCOVERED.equals(intent.getAction()))
|| (NfcAdapter.ACTION_TAG_DISCOVERED.equals(intent.getAction()))
|| (NfcAdapter.ACTION_TECH_DISCOVERED.equals(intent.getAction()))) {
String payload = intent.getDataString();
mTagContentText.setText("act:" + sAction + "\n" + "pload:" + payload + "\n" + intentToText(intent));
Tag myTag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
if (myTag != null) {
trace("myTag.mId:" + byteArrayToHex(myTag.getId()));
mTagContentText.setText(mTagContentText.getText() + "\n" + "myTag.mId:" + byteArrayToHex(myTag.getId()));
android.os.Parcelable[] rawMsgs = intent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES);
if (rawMsgs != null) {
for (android.os.Parcelable p : rawMsgs) {
NdefMessage msg = (NdefMessage) p;
NdefRecord[] records = msg.getRecords();
for (NdefRecord record : records) {
short tnf = record.getTnf();
byte[] id = record.getId();
byte[] payLoad = record.getPayload();
}
}
}
}
}
}
/**/
#Override
protected void onResume() {
super.onResume();
trace("onResume...");
if (mNfcAdapter != null) {
try {
// See if the Activity is being started/resumed due to an NFC event and handle it
onNewIntent( getIntent());
}
catch (Throwable t) {
traceFails(t);
}
try {
mMessage = "mNfcAdapter.disableForegroundDispatch";
mNfcAdapter.disableForegroundDispatch(FullscreenActivity.mInstance);
traceOk();
}
catch (Throwable t) {
traceFails(t);
}
}
}
/**/
#Override
protected void onPause() {
super.onPause();
trace("onPause...");
}
}
AndroidManifest.xml is :
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.pdf.nfcaccess">
<uses-permission android:name="android.permission.NFC" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<application
android:allowBackup="true"
android:icon="#mipmap/ic_pdflauncher"
android:label="#string/app_name"
android:supportsRtl="true"
android:debuggable="true"
android:theme="#style/AppTheme">
<activity
android:name=".FullscreenActivity"
android:configChanges="orientation|keyboardHidden|screenSize"
android:label="#string/app_name"
android:theme="#style/FullscreenTheme">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
<intent-filter>
<action android:name="android.nfc.action.NDEF_DISCOVERED" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
<intent-filter>
<action android:name="android.nfc.action.TECH_DISCOVERED" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
<intent-filter>
<action android:name="android.nfc.action.TAG_DISCOVERED" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
<!--intent-filter>
<action android:name="android.nfc.action.NDEF_DISCOVERED" />
<category android:name="android.intent.category.DEFAULT" />
<data android:mimeType="text/plain"/>
</intent-filter-->
</manifest>

You receive the NFC intent (action TAG_DISCOVERED) because you registered for it in the manifest:
<intent-filter>
<action android:name="android.nfc.action.TAG_DISCOVERED" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
This is also the reason why your activity is recreated upon receiving the intent.
The intent filter that you register for the foreground dispatch (action NDEF_DISCOVERED with any MIME type) does not seem to match your tag (or you did not yet invoke the piece of code that would enable the foreground dispatch).
Note that calling disableForegroundDispatch() will ony disable a foreground dispatch previously registered through enableForegroundDispatch(). It will not influence the intent filters in your manifest. See Android: Can I enable/disable an activity's intent filter programmatically? on how you could selectively disable intent filters registered in the manifest. However, with regard to NFC intents, you would probably want to register to receive events for all tags through the foreground dispatch system and then, upon receiving the event in onNewIntent() selectively ignore tags that you don't want.
A few more things about your code (actually only about the NFC parts)
For the NDEF_DISCOVERED intent filter in your manifest you would typically also want to specify a <data ... /> element that matches the data type of your tags.
Do not use a TAG_DISCOVERED intent filter in your manifest (unless you really understand and want the impact of this). The TAG_DISCOVERED intent filter (when used in the manifest) is merely a compatibility mode for API level 9 (before Android 2.3.3) where NFC support was very, very limited and a fall-back mode that can be used to create apps that handle NFC tags that are not supported by any other app.
The TECH_DISCOVERED intent filter requires a tech-list XML file in order to match any tag. Thus, your current version of this filter in your manifest will never match anything.
Calling disableForegroundDispatch() in onResume() does not make any sense. By design, the foreground dispatch could never be enabled at this point of the activity life-cycle. The reason for this is that you must not call enableForegroundDispatch() before onResume() and you are required to call disableForegroundDispatch() at latest in onPause().
In fact it does not make sense to use enableForegroundDispatch() / disableForegroundDispatch() anywhere other than in onResume() / onPause(). If you want to stop listening for tags upon other events (e.g. a pressing a button), you would simply remember your current state (process/don't process NFC events) in some flag and, when you receive a new NFC intent in onNewIntent(), you would either process or silently ignore the tag based n that flag.
Your code should not manually call activity life-cycle methods (as you currently do with onNewIntent(getIntent());).