Develop Reference

Set Receive Intent back to Default Value in Android using Java

FirstActivity.java
startActivity(new Intent(FirstActivity.this, SecondActivity.class)
.putExtra("passed_value", true));
SecondActivity.java
#Override
public void onPageFinished(final WebView view, String url) {
if(getIntent().getBooleanExtra("passed_value", false)){
}
}
After receiving intent value from FirstActivity.java every reload it runs the if block . But i need this intent to run only in onPageFinished method.
So how to run if block only when it comes from FirstActivity.java. Is there any way so that i can make this intent value back to default value after if block executed?

In your SecondActivity create a class level variable as boolean passed_value = false;
Then in your onCreate(), change its value like - passed_value = getIntent().getBooleanExtra("passed_value", false);
Finally you can use it like -
#Override
public void onPageFinished(final WebView view, String url) {
if(passed_value){
}
}

A fairly straight forward method would be to have a Boolean passedValue variable that you instantiate with the intent extra in onCreate, and then set as false in the if block. Something along the following lines should work,
public class SecondActivity extends AppCompatActivity {
Boolean passedValue;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
passedValue = getIntent().getBooleanExtra("passed_value", false);
//Other code things
}
#Override
public void onPageFinished(final WebView view, String url) {
if(passedValue){
//Do what you need to do
passedValue = false
}
}
}

SavedIntanceState.getBoolean() is making my app crash (i think)

My Goal:
So I need help putting a boolean primitives into a bundle and retrieving it from the bundle when there is a screen orientation change in Android. I am using that boolean value in a conditional statement that helps decide if 2 Button views (mTrueButton, mFalseButton) should be enabled or not. What i have so far is causing the app to shut down (aka crash) when there is a screen rotation. I think I am not retrieving or writing my boolean from my bundle or into my bundle correctly, and it is causing the app to crash.
How The App Should Works:
When a user touches the mTrueButton or mFalseButton button to answer a question, both buttons become disabled so the user is not allowed to answer again. I want those buttons to keep being disabled when the user answers and then rotates the screen.**
I know that when a user rotates their Android device, onDestroy() is called because runtime configuration changes take place, causing the app to be relaunched without having knowledge of it's previous state, (unless store my necessary data onto a bundle and pass it onto my onCreate method).
These are SOME global variables in my activity class
private int index = 0;
priavate Button mTrueButton,mFalseButton;
private static final String KEY_INDEX = "index";
private static final String BTTN_ENABLED = "bttnEnabled";
private boolean trueFalseButtonsEnabled = true;
These are SOME statements in my onCreate() method of the same activity class
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG, "onCreate(Bundle) called");
setContentView(R.layout.activity_quiz);
if(savedInstanceState != null) {
index = savedInstanceState.getInt(KEY_INDEX, 0);
changeButtonEnableStatus(savedInstanceState.getBoolean(BTTN_ENABLED,true));
}
mTrueButton = (Button)findViewById(R.id.true_button);
mFalseButton = (Button)findViewById(R.id.false_button);
mTrueButton.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v){
checkAnswer(true);
changeButtonEnableStatus(false);
}
});
mFalseButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
checkAnswer(false);
changeButtonEnableStatus(false);
}
});
}
These are SOME methods in the same activity class but not in my onCreate()
private void changeButtonEnableStatus(boolean bool){
trueFalseButtonsEnabled = bool;
mTrueButton.setEnabled(bool);
mFalseButton.setEnabled(bool);
}
#Override
public void onSaveInstanceState(Bundle savedInstanceState){
super.onSaveInstanceState(savedInstanceState);
Log.d(TAG,"onSavedInstanceState() called");
savedInstanceState.putInt(KEY_INDEX,index);
savedInstanceState.putBoolean(BTTN_ENABLED, trueFalseButtonsEnabled);
}
Note that:
index = savedInstanceState.getInt(KEY_INDEX, 0);
works properly. It is setting global variable "index" to equal to the int primitive what was stored in into keywork "KEY_INDEX".
However I don't think: changeButtonEnableStatus(savedInstanceState.getBoolean(BTTN_ENABLED,true)); is working properly. My app seems to crash when I include that statement and run the app, and then rotate the device.

How do I add data I have keyed in a EditText box into an array to list in another activity?

Below are the 3 java classes which I am using for my android application development. I would like to add the student data (name and phone number) from the AddActivity to be stored in MainActivity page after clicking "Add". I have researched on this and tried using an array. But I am quite confused on how the logic must be for the code to send the data keyed in AddActivity into the MainActivity page. Can anyone give me a guidance on how to work this out and would really be grateful if you could show me another way rather the way I am trying. I want the data to be stored in a ListView format in the MainActivity after each "Add" I have clicked in the AddActivity page. I do hope that someone will be able to guide me in doing this. Thank you.
MainActivity.java -
https://jsfiddle.net/eb1fprnn/
public class MainActivity extends AppCompatActivity {
ListView listView;
Button addStudent;
ArrayList<Student> students = new ArrayList<Student>();
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
add();
}
public void add() {
Student student;
addStudent = (Button) findViewById(R.id.add);
addStudent.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, AddActivity.class);
startActivity(intent);
}
});
}
}
AddActivity.java -
https://jsfiddle.net/40k5mas2/
public class AddActivity extends AppCompatActivity {
EditText name, phone;
Button add;
int FphoneNumber;
String Fname;
ArrayList<Student> students;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent intent = getIntent();
students = (ArrayList<Student>) getIntent().getSerializableExtra("AddNewStudent");
setContentView(R.layout.activity_add);
edit();
addStudent();
}
public void edit() {
name = (EditText) findViewById(R.id.StudentName);
phone = (EditText) findViewById(R.id.phone);
final Button addStudent = (Button) findViewById(R.id.AddStudent);
name.addTextChangedListener(new TextWatcher() {
#Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
#Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
addStudent.setEnabled(!name.getText().toString().trim().isEmpty());
Fname = name.getText().toString();
String phoneNumber = phone.getText().toString();
FphoneNumber = Integer.parseInt(phoneNumber);
}
#Override
public void afterTextChanged(Editable s) {
}
});
}
public void addStudent() {
add = (Button) findViewById(R.id.AddStudent);
add.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(AddActivity.this, MainActivity.class);
intent.putExtra("studentName",name.getText().toString() );
intent.putExtra("phoneNumber",phone.getText().toString());
startActivity(intent);
Student student = new Student(Fname, FphoneNumber);
students.add(student);
}
});
}
public void addStudent(){
add = (Button) findViewById(R.id.AddStudent);
add.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(AddActivity.this,Record.class);
startActivity(intent);
}
});
}
Student.java -
https://jsfiddle.net/gy0g7b0s/
public class Student {
String mName;
int mPhoneNumber;
public Student (String name, int number){
mName = name;
mPhoneNumber = number;
};
public String getmName() {
return mName;
}
public String getmName(String newName) {
return (this.mName = newName);
}
public int getmPhoneNumber() {
return this.mPhoneNumber;
}
public int getmPhoneNumber(int newPhoneNumber) {
return (this.mPhoneNumber = newPhoneNumber);
}
#Override
public String toString() {
return String.format("%s\t%f",this.mName, this.mPhoneNumber);
}
[1] : [Image of Main Activity Page] http://imgur.com/a/pMWt4
[2] : [Image of Add Activity Page] http://imgur.com/a/8YvVc

as mentioned above, the correct way would be to use the startActivityForResult method. Check this.
And how to go about it, Damn easy!
Modifying your code:
public void add() {
Student student;
addStudent = (Button) findViewById(R.id.add);
addStudent.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, AddActivity.class);
startActivityForResult(intent,123);
}
});
}
}
and in the same activity (MainActivity) listen for the result
Also would recommend you to use the parceler.org lib for sending objects
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode== Activity.RESULT_OK && requestCode==123){
// perform your list addition operation here and notify the adapter for change
// the returned data comes in 'data' parameter and would recommend you to use parcels.org lib
// for sending parcelable pojo across activities and fragments.
list.add(Parcels.unwrap(data.getParcelableArrayExtra(YOUR_KEY)));
adapter.notifyDataSetChanged();
}
}
And in your AddActivity, when you add just do this.
public void addStudent() {
// add the 'add' button view to the oncreatemethod
// add = (Button) findViewById(R.id.AddStudent);
add.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// Do not restart the activity that opened this activty
// this activity is anyways on top of the MainActivity. Just finish this activty setting the result
// Intent intent = new Intent(AddActivity.this, MainActivity.class);
// intent.putExtra("studentName",name.getText().toString() );
// intent.putExtra("phoneNumber",phone.getText().toString());
// startActivity(intent);
// How to do that?
Student student = new Student(Fname, FphoneNumber);
Intent intent = new Intent();
intent.putExtra(YOUR_KEY, Parcels.wrap(student));
// you can also do it without the parcels lib
// intent.putExtra("studentName",name.getText().toString() );
// intent.putExtra("phoneNumber",phone.getText().toString());
setResult(123,intent); // set the result code. it should be the same one as the one your listening on in MainAcitivty
// then just finish this activity.
finish();
// this calls the onActivtyResultMethod in MainActivity which furtther does the logic
// students.add(student);
}
});
}
That should work! Cheers!

Use StartActivityForResult for AddActivity and return object from here and use in MainActivity. For example see here

Since you store the data in a file, the add activity should just write the data to the file. Then the main activity should always read the file to refresh the list.

I will suggest using a static class if you don't want to use a Database.
Or if you should use a file is just very simple to write into a file when you add and read from it in the next activity.
Just create a Static class like this.
public static class MyStaticClass{
private static ArrayList <Student> mStudents = new ArrayList<Student>()
public static void addStudent(Student theNewStudent){
mSudents.add(theNewStudent);
}
public static List<Student> getStudents(){
return mStudents;
}
}
or with a file:
public static class MyFileClass{
private static String pathFile = "Your path";
public static void addStudent(Student theNewStudent){
File file = new OutputStreamWriter(new FileOutputStream(pathFile,true)); //the true is to append to the file
file.write(/*parse your student as a string*/);
file.close();
}
public static List<Student> getStudents(){
ArrayList<Student> students = new ArrayList<>()
File file = new File(pathFile);
Scanner sc = new Scanner(file);
while (sc.hasNextLine()) {
String line = sc.nextLine();
//parse your line to a student object
students.add(yourNewStudent);
}
sc.close();
return students;
}
}
Just call the add student and the get students in the proper class as follows.
MyStaticClass.addStudent(student);
or
MyFileClass.addStudent(student);
Hope it helps.
In your onclick listener:
public void onClick(View v) {
Intent intent = new Intent(AddActivity.this, MainActivity.class);
Student student = new Student(Fname, FphoneNumber);
MyStaticClass.addStudent(student); // or the FileClass
startActivity(intent);
}
and i cant see where do you retrieve the list. but just use the getStudents of the class.

Intent yourFirstAct= new Intent(firstAct.this,second.class);
yourFirstAct.putExtra("","");
startActivitForResult(yourFirstAct);
in first Activity,
#Override
public void onAcitivityResult(....){
super();
}
in your second activity when you done,
do your stuff whatever you want in second activity. and pass it to mainActivity
Intent yoursecAct= new Intent();
yourSecAct.putExtra("","");
setResult(yourSecAct);
finish();
IF YOU ARE USING IN FRAGMENT
if you do startActivityResult() in fragment means,
your fragment mainActivity must return super() in
public void onAcitivityResult(...){super()}

After getting the details from the student, put the respective details in a bundle and just use intent to go back to the main activity. Then use bundles to extract the data in the main activity.

You can use startActivityForResult for the same. if you haven't found the answer yet then please let me know. I will provide you the code.
Many above answers already defined this thing in a very good way.

This is about communication between Activities. You can use event bus to realize this.
https://github.com/JackZhangqj/EventBus
Then 1. Add event bus dependency to the App's build.grade
compile "de.greenrobot:eventbus:3.0.0
Register and unregister your subscribe in the MainActivity.java
#Override
protected void onStart() {
super.onStart();
EventBus.getDefault().register(this);
}
#Override
protected void onStop() {
super.onStop();
EventBus.getDefault().unregister(this);
}
3.Post event in the AddActivity.java
EventBus.getDefault().post(new Student(name.getText().toString(), phone.getText().toString()));
4.Implement event handling method in MainActivity
//The student is the added student in the AddActivity.java
public void onEventMainThread(Student student) {
}

To kind of expand a little bit on MadScientist's answer, ListView's need adapters in order set the data in it's view. You'll need to define an ArrayAdapter for your list view to communicate with. This will need to go in your MainActivity and will be initialized in the onCreate method. Assuming you want to display both types of information, you'll need to construct your adapter with the built in layout for showing two items via android.R.layout.simple_list_item_2. If you would like to create your own layout, however, you can look up how to do that here.
public class MainActivity extends AppCompatActivity {
Button addStudent;
ArrayAdapter<Student> adapter;
ArrayList<Student> students = new ArrayList<Student>();
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_2, students);
ListView listView = (ListView) findViewById(R.id.listView);
listView.addAdapter(adapter);
add();
}
Call the startActivityForResult(intent, 123) in your Listener to start the new activity. Then, once you have typed in your data, add your items to the intent and call finish() in your AddActivity. Override the onActivityResult in your MainActivity to pull the items off your intent and add them to your list. Finally, notify the adapter of the changes via adapter.notifyDataSetChanged()

How initialize correctly static variable in PreferenceActivity

I have Preference class extent PreferenceActivity.
I create public static String quality; in Preference.class i add in onCreate
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.pref);
quality = "QUALITY_HIGH";//initialize
}
and add in Preference.class this method
public void getQuality() {
if (keyquality.equals("480p")) {
quality = "QUALITY_LOW";
//
}
if (keyquality.equals("720p")) {
//
quality = "QUALITY_720P";
}
if (keyquality.equals("1080p")) {
//
quality = "QUALITY_HIGH";
}
}
in another class i create method to get my variable and set settings
private void getqualityvideo() {
/*if (Prefernce.quality == null) {
preferencecamrecoder = CamcorderProfile.get(CamcorderProfile.QUALITY_HIGH);
} else {*/
if (Prefernce.quality.equals("QUALITY_LOW")) {
preferencecamrecoder = CamcorderProfile.get(CamcorderProfile.QUALITY_LOW);
}
if (Prefernce.quality.equals("QUALITY_720P")) {
preferencecamrecoder = CamcorderProfile.get(CamcorderProfile.QUALITY_720P);
}
if (Prefernce.quality.equals("QUALITY_HIGH")) {
preferencecamrecoder = CamcorderProfile.get(CamcorderProfile.QUALITY_HIGH);
}
// }
}
Problem:
when start application
private void startServes() {
btnStart = (ImageView) findViewById(R.id.StartService);
btnStart.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
v.startAnimation(mAnimationImage);
Intent intent = new Intent(MainActivity.this, RecorderService.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startService(intent);
changeCamera
.setEnabled(false);
btnStart.setEnabled(false);
setings.setEnabled(false);
moveTaskToBack(false);
}
});
}
in another class in method
getqualityvideo() error NullPointerException
error in this first line
if (Prefernce.quality.equals("QUALITY_LOW"))
why the quality variable is empty?

The reason is that you're setting Preference.quality in the onCreate method in your Preference class. So what's probably happening is that when you start your application in your other class, Preference.quality is going to be null because it was never initialized to anything. The reason is that the other class has no way to access the onCreate method in your Preference class as of now. onCreate is executed when an activity starts, but that doesn't seem to happen anywhere in your code. A solution could be to initialize public static String quality outside of your onCreate method but still within the Preference class,
public static String quality = "QUALITY_HIGH";
#Override
public void onCreate(Bundle savedInstanceState) {
//insert code here
}
The problem was merely a scope issue.

While using the IntentIntegrator from the ZXing library, can I add a flash button to the barcode scanner via the Intent?

I am scanning barcodes and QR codes from an Android app via Intent using the ZXing Library and its port of the Android Application. I added the following two lines in my Gradle dependencies to use the android-integration code without modification:
compile 'com.journeyapps:zxing-android-embedded:3.2.0#aar'
compile 'com.google.zxing:core:3.2.1'
And I am using IntentIntegrator in my Activity to scan a barcode in the onCreate() like this:
integrator = new IntentIntegrator(this);
integrator.setOrientationLocked(false);
integrator.setPrompt(getString(R.string.scanner_text)); // Set the text of the scanner
integrator.setCameraId(0); // Use a specific camera of the device
integrator.setBeepEnabled(true); // Enable beep in the scanner
integrator.setBarcodeImageEnabled(false); // Do not fetch image from the camera
integrator.initiateScan();
Everything works and I get correct scanned result, but I want a flash button in the lower right corner of the scanner like this:
I can already control the flash using the volume up and down keys because I override the CaptureActivity.
Is a flash button like the one above already there in the barcode scanner which can switch between AUTO, ON and OFF mode? If there is, can I use the addExtra() method of the IntentIntegrator to activate it? Or is the only way to implement this would be to modify the entire code according to my needs?

I had overlooked this page on Embedding BarcodeView and these sample activities which show how to customise the Barcode Scanner according to your needs. The example activity that helped me was CustomScannerActivity.
There isn't a option in the IntentIntegrator class to implement a flash button natively. Instead I should make a custom layout for the Barcode Scanner, use it in a custom activity and call this activity from the IntentIntegrator.
I have two activities. One is the ScannerActivity and other one is the CallingActivity. A mistake that confused me for a while was that I created an instance of IntentIntegrator in the onCreate() method of ScannerActivity. It should be in the CallingActivity.
In the example given a Button is used and the text of the Button is changed according to the flash. I created a new Android Layout called activity_custom_scanner where I replaced the Button with a ToggleButton and used images for the button instead to get my desired Flash On/Off Button.
So my ScannerActivity looks like this:
public class CustomScannerActivity extends Activity implements
CompoundBarcodeView.TorchListener {
private static final int BarCodeScannerViewControllerUserCanceledErrorCode = 99991;
private static final String TAG = CustomScannerActivity.class.getSimpleName();
private CaptureManager capture;
private CompoundBarcodeView barcodeScannerView;
private ToggleButton switchFlashlightButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_custom_scanner);
barcodeScannerView = (CompoundBarcodeView)findViewById(R.id.zxing_barcode_scanner);
barcodeScannerView.setTorchListener(this);
switchFlashlightButton = (ToggleButton)findViewById(R.id.switch_flashlight);
switchFlashlightButton.setText(null);
switchFlashlightButton.setTextOn(null);
switchFlashlightButton.setTextOff(null);
// if the device does not have flashlight in its camera,
// then remove the switch flashlight button...
if (!hasFlash()) {
switchFlashlightButton.setVisibility(View.GONE);
}
switchFlashlightButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
// Save the state here
if (isChecked) {
barcodeScannerView.setTorchOn();
} else {
barcodeScannerView.setTorchOff();
}
}
});
capture = new CaptureManager(this, barcodeScannerView);
capture.initializeFromIntent(getIntent(), savedInstanceState);
capture.decode();
}
#Override
protected void onResume() {
super.onResume();
capture.onResume();
}
#Override
protected void onPause() {
super.onPause();
capture.onPause();
}
#Override
protected void onDestroy() {
super.onDestroy();
capture.onDestroy();
}
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
capture.onSaveInstanceState(outState);
}
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
return barcodeScannerView.onKeyDown(keyCode, event) || super.onKeyDown(keyCode, event);
}
/**
* Check if the device's camera has a Flashlight.
* #return true if there is Flashlight, otherwise false.
*/
private boolean hasFlash() {
return getApplicationContext().getPackageManager()
.hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH);
}
#Override
public void onTorchOn() {
// necessary override..
}
#Override
public void onTorchOff() {
// necessary override..
}
}
And the CallingActivity looks like this:
public class CallingActivity extends Activity {
private static final String TAG = CallingActivity.class.getSimpleName();
private static final int BarCodeScannerViewControllerUserCanceledErrorCode = 99991;
String uuid;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
uuid = getIntent().getStringExtra("uuid");
new IntentIntegrator(this).setOrientationLocked(false).setCaptureActivity(CustomScannerActivity.class).initiateScan();
}
public void onActivityResult(int requestCode, int resultCode, Intent intent) {
IntentResult scanResult = IntentIntegrator.parseActivityResult(requestCode, resultCode, intent);
if (resultCode == RESULT_OK) {
if (scanResult != null) {
// handle scan result
Log.i(TAG, "Text from Barcode Scanner: " + scanResult.getContents());
getIntent().putExtra("data", scanResult.getContents());
getIntent().putExtra("uuid", uuid);
}
}
else if (resultCode == RESULT_CANCELED) {
getIntent().putExtra("error", "User canceled");
getIntent().putExtra("error_code", BarCodeScannerViewControllerUserCanceledErrorCode);
}
else
{
getIntent().putExtra("error", getString(R.string.scanner_error));
getIntent().putExtra("error_code", BarCodeScannerViewControllerUserCanceledErrorCode);
}
setResult(resultCode, this.getIntent());
this.finish();
}
}
I am not sure if it's the perfect way, but that's how I did it.
Hope it helps someone!

There is a setTorchOn method in CompoundBarcodeView so you can check that method out and try to implement it for your needs. Hope it helps.

This question is probably too old, but you can use the Volume buttons to turn on/off the torch while scanning.