In the main activity, I have LiveData which contains members and a click listener. If I click on a member, then his ID is passed with intent.putExtra. That ID is later passed on to the method open in this activity. With this activity, I want to see the details of a member. In my MemberInfo activity, I marked a line where my problem lies.
It shows me this error: Cannot access database on the main thread since it may potentially lock the UI for a long period of time.
My DAO consists this code:
#Query("SELECT * FROM member_table WHERE MemberID=:id")
Member getMemberInfo(long id);
This is my main activity:
public class MemberMainActivity extends AppCompatActivity implements MemberListAdapter.MemberClickListener{
private MemberViewModel mMemberViewModel;
private List<Member> mMember;
void setMember(List<Member> members) {
mMember = members;
}
public static final int NEW_MEMBER_ACTIVITY_REQUEST_CODE = 1;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_member);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(MemberMainActivity.this, NewMemberActivity.class);
startActivityForResult(intent, NEW_MEMBER_ACTIVITY_REQUEST_CODE);
}
});
RecyclerView recyclerView = findViewById(R.id.recyclerviewcard_member);
final MemberListAdapter adapter = new MemberListAdapter(this);
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
mMemberViewModel = ViewModelProviders.of(this).get(MemberViewModel.class);
mMemberViewModel.getAllMember().observe(this, new Observer<List<Member>>() {
#Override
public void onChanged(#Nullable final List<Member> members) {
mMember = members;
// Update the cached copy of the words in the adapter.
adapter.setMember(members);
}
});
}
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == NEW_MEMBER_ACTIVITY_REQUEST_CODE && resultCode == RESULT_OK) {
Member member = new Member(data.getStringExtra(NewMemberActivity.EXTRA_REPLY), data.getStringExtra(NewMemberActivity.EXTRA_REPLY2));
mMemberViewModel.insert(member);
} else {
Toast.makeText(
getApplicationContext(),
R.string.empty_not_saved,
Toast.LENGTH_LONG).show();
}
}
public void onMemberClick(int position) {
Member member = mMember.get(position);
Intent intent = new Intent(getApplicationContext(),MemberInfo.class);
intent.putExtra("MemberID", member.getId());
MemberInfo.open(this, member.getId());
}
}
This is my activity:
public class MemberInfo extends AppCompatActivity {
public static void open(Activity activity, long memberid) {
Intent intent = new Intent(activity, MemberInfo.class);
intent.putExtra("MemberID", memberid);
activity.startActivity(intent);
}
private List<Member> mMember;
private MemberViewModel mMemberViewModel;
void setMember(List<Member> members){
mMember = members;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_memberinfo);
Log.i("okay", "memberinfo");
Intent intent = getIntent();
if (intent != null && intent.hasExtra("MemberID")) {
long memberid = intent.getLongExtra("MemberID", -1);
// TODO: get customer details based on customer id
TextView firstname = findViewById(R.id.layout_memberfirstname);
TextView surname = findViewById(R.id.layout_membersurname);
TextView balance = findViewById(R.id.layout_memberbalance);
-------------Member member = MemberRoomDatabase.getDatabase().memberDao().getMemberInfo(memberid);-------------
firstname.setText(member.getFirstname());
surname.setText(member.getSurname());
}
else {
Toast.makeText(
getApplicationContext(),
R.string.empty_not_saved,
Toast.LENGTH_LONG).show();
}
}
}
I thought that maybe it is because I'm missing a AsyncTask method. I tried this, but this also didn't work:
private static class insertMemberInfoAsyncTask extends AsyncTask<Member, Void, Void> {
private MemberDao mAsyncTaskDao;
insertMemberInfoAsyncTask(MemberDao dao) {
mAsyncTaskDao = dao;
}
#Override
protected Void doInBackground(Member... params) {
Member member = params[0];
mAsyncTaskDao.getMemberInfo(member.getId());
return null;
}
}
public Member getMemberInfo(long id) {
mAllMember = mMemberDao.getAllMember();
Member member = mMemberDao.getMemberInfo(id);
new insertMemberInfoAsyncTask(mMemberDao).execute(member);
return member;
}
I think I use the method wrong. Can anybody help me?
One option is to update your query to this:
#Query("SELECT * FROM member_table WHERE MemberID=:id")
LiveData<Member> getMemberInfo(long id);
(or similar, using Flowable). This avoids the need to manually create your own AsyncTask.
Returning the LiveData wrapper around the Member type automatically signals to Room that the query can/should be performed asynchronously. Per https://developer.android.com/training/data-storage/room/accessing-data (my emphasis):
Note: Room doesn't support database access on the main thread unless you've called allowMainThreadQueries() on the builder because it might lock the UI for a long period of time. Asynchronous queries—queries that return instances of LiveData or Flowable—are exempt from this rule because they asynchronously run the query on a background thread when needed.
You can use Future and Callable. So you would not be required to write a long asynctask and can perform your queries without adding allowMainThreadQueries() or using LiveData.
My dao query:-
#Query("SELECT * from user_data_table where SNO = 1")
UserData getDefaultData();
My repository method:-
public UserData getDefaultData() throws ExecutionException, InterruptedException {
Callable<UserData> callable = new Callable<UserData>() {
#Override
public UserData call() throws Exception {
return userDao.getDefaultData();
}
};
Future<UserData> future = Executors.newSingleThreadExecutor().submit(callable);
return future.get();
}
In my case, it works if you add Dispatcher.IO when you use coroutines:
viewModelScope.launch(Dispatchers.IO) {
//your database call
}
For me allowMainThreadQueries() works.
This allows room to support database access on the main thread.
See the following code
#Database(entities = [Word::class ],version = 1)
abstract class VocabularyDatabase:RoomDatabase() {
companion object {
private lateinit var INSTANCE:VocabularyDatabase
fun getInstance(context:Context):VocabularyDatabase= Room.databaseBuilder(
context,
VocabularyDatabase::class.java,
"vocabulary"
)
.createFromAsset("vocabulary.db")
.allowMainThreadQueries()
.build()
}
abstract fun dao():WordDao
}
Using Future and Callables can be an alternative here. By using Future and Callable you can get rid of AsyncTask and forcing your queries to the main thread.
The syntax would be as follow -
#Throws(ExecutionException::class, InterruptedException::class)
private fun canContinue(id: String): UserData{
val callable = Callable { userDao.getDefaultData() }
val future = Executors.newSingleThreadExecutor().submit(callable)
return future!!.get()
}
And, don't forget the null check for the data returned. Because it might be null
Related
I programmed a Vocabulary Trainer with Vocabulary Cards. The Vocabulary Cards are Entries in a Room Database created from an asset. I am displaying these Vocabulary Cards with ViewPager2 in an Activity. I have a 'correct' and a 'false' button and when the user clicks on either, I want to update the Vocabulary Card (-> The entry in the sqlite database) and automatically swipe to the next item of the ViewPager2.
If I implement the buttons in the ViewPager2Adapter, I can't find a way to change the position of the ViewPager2. If I implement the buttons in the activity the sqlite entry does not update properly (After it updates the entry, the activity is constantly refreshed, it seems like it never the leaves the OnClick methode of the button).
So is it possible to change the position of ViewPager2 from inside the ViewPager2Adpater?
Thanks for your help!
That is the relevant code if I have the buttons in my ViewPager2Adapter. Here I don't know how to change the position of the ViewPager2
public void onBindViewHolder(#NonNull #NotNull ViewHolder holder, int position) {
VocabularyCard vocabularyCard = currentCards.get(position);
holder.btn_correct.setOnClickListener(view -> {
vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard);
});
holder.btn_false.setOnClickListener(v15 -> {
vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard);
});
That is the relevant code if I have the buttons in the Activity. Here the update function triggers an infinite updating of the Activity:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
initAll();
btn_correct_2.setOnClickListener(view -> {
int currentPos = viewpager2.getCurrentItem();
vocabularyViewModel.getCurrentCards().observe(this, vocabularyCards -> {
if (vocabularyCards.size() == currentPos){
Intent intent = new Intent(TestActivity.this, MainActivity.class);
startActivity(intent);
}else {
viewpager2.setCurrentItem(currentPos + 1);
}
VocabularyCard vocabularyCard = vocabularyCards.get(currentPos);
vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard);
});
});
btn_false_2.setOnClickListener(view -> {
int currentPos = viewpager2.getCurrentItem();
vocabularyViewModel.getCurrentCards().observe(this, vocabularyCards -> {
if (vocabularyCards.size() == currentPos){
Intent intent = new Intent(TestActivity.this, MainActivity.class);
startActivity(intent);
}else {
viewpager2.setCurrentItem(currentPos + 1);
}
VocabularyCard vocabularyCard = vocabularyCards.get(currentPos);
vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard);
});
});
Objects.requireNonNull(getSupportActionBar()).setTitle(getResources().getString(R.string.learn_new_words));
LiveData<List<VocabularyCard>> allNewCards = vocabularyViewModel.getAllNewCards(goal);
allNewCards.observe(this, vocabularyCards -> vocabularyViewModel.setCurrentCards(vocabularyCards));
vocabularyViewModel.getCurrentCards().observe(this, vocabularyCards -> {
viewPager2Adapter.setCurrentCards(vocabularyCards);
viewpager2.setAdapter(viewPager2Adapter);
viewpager2.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
super.onPageScrolled(position, positionOffset, positionOffsetPixels);
}
#Override
public void onPageSelected(int position) {
super.onPageSelected(position);
}
#Override
public void onPageScrollStateChanged(int state) {
super.onPageScrollStateChanged(state);
}
});
});
The update function in the Room DAO is straightforward:
#Update
void updateSingleVocabularyCard(VocabularyCard vocabularyCard);
I left out all the code that is not relevant.
There are several ways to propagate an event from the adapter to the activity where you manage your cards using ViewPager2. Let's have a look how it can be done either using an interface or using the same view model. But in any case I strongly recommend you to update your database in a background thread to prevent any possible UI lags.
1. Using an interface
This option is more flexible since you can propagate events as well as pass data as parameters. You can also reuse this interface for other cases. As far as I See you have a holder that has 2 buttons for the users to make choices. So our event here would be something like ChoiceEventListener, let's call this interface like so. Then you'd have to add a method to handle this event from within anywhere you wanna hear this event, and let's call its handle method onChoice(). Finally we would need a variable to indicate what the choice is. Now that ready to implement, let's write the new interface...
ChoiceEventListener.java
public interface ChoiceEventListener {
void onChoice(VocabularyCard vocabularyCard, boolean choice);
}
The next thing to do is to implement this interface where you want to listen to this event. In this case it is in your activity. There are 2 ways to do this:
You make your activity to inherit its methods using the implements keyword
YourActivity.java
public class YourActivity extends AppCompatActivity implements ChoiceEventListener {
// Use a background thread for database operations
private Executor executor = Executors.newSingleThreadExecutor();
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
initAll();
// You must construct your adapter class with the listener
ViewPager2Adapter adapter = new ViewPager2Adapter(/* Other params... */, this);
}
#Override
public void onChoice(VocabularyCard vocabularyCard, boolean choice) {
if(choice) {
// User pressed the correct button
}
else {
// User pressed the false button
}
// Update card in the background
executor.execute(()-> vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard));
}
}
You can implement it as an anonymous function
YourActivity.java
public class YourActivity extends AppCompatActivity {
// Use a background thread for database operations
private Executor executor = Executors.newSingleThreadExecutor();
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
initAll();
// You must construct your adapter class with the listener
ViewPager2Adapter adapter = new ViewPager2Adapter(/* Other params... */, (vocabularyCard, choice) -> {
if(choice) {
// User pressed the correct button
}
else {
// User pressed the false button
}
// Update card in the background
executor.execute(()-> vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard));
});
}
}
Finally the ViewPager2Adapter class implementation would be something like this:
ViewPager2Adapter.java
public class ViewPager2Adapter extends RecyclerView.Adapter<ViewPager2ViewHolder> {
// Here is your listener to deliver the choice event to it
private final ChoiceEventListener listener;
// Constructor
public ViewPager2Adapter(/* Other params... */, ChoiceEventListener listener) {
/* Other inits */
this.listener = listener;
}
public void onBindViewHolder(#NonNull #NotNull ViewHolder holder, int position) {
VocabularyCard vocabularyCard = currentCards.get(position);
holder.btn_correct.setOnClickListener(view -> {
listener.onChoice(vocabularyCard, true); // true for correct
});
holder.btn_false.setOnClickListener(v15 -> {
listener.onChoice(vocabularyCard, false); // false for false :)
});
}
}
2. Use the ViewModel for inter-communication
In this option we use a LiveData object to make page switching. The only thing you need to know in your activity is the current position which you get it from the adapter class. Once you update it in the adapter, set the current position value in live data so that you can switch the page in your activity.
VocabularyViewModel.java
public class VocabularyViewModel extends ViewModel {
public MutableLiveData<Integer> mldCurrentPosition = new MutableLiveData<>(0);
}
YourActivity.java
public class YourActivity extends AppCompatActivity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
initAll();
vocabularyViewModel.mldCurrentPosition().observe(this, currentPosition -> {
if(currenPosition == null) return; // ignore when null
viewpager2.setCurrentItem(currentPosition + 1);
}
}
}
Finally the ViewPager2Adapter class implementation would be something like this:
ViewPager2Adapter.java
public class ViewPager2Adapter extends RecyclerView.Adapter<ViewPager2ViewHolder> {
// Use a background thread for database operations
private Executor executor = Executors.newSingleThreadExecutor();
public void onBindViewHolder(#NonNull #NotNull ViewHolder holder, int position) {
VocabularyCard vocabularyCard = currentCards.get(position);
holder.btn_correct.setOnClickListener(view -> {
// Update card in the background
executor.execute(()-> vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard));
// Then invoke switching to the next card
vocabularyViewModel.mldCurrentPosition.setValue(position + 1);
});
holder.btn_false.setOnClickListener(v15 -> {
// Update card in the background
executor.execute(()-> vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard));
// Then invoke switching to the next card
vocabularyViewModel.mldCurrentPosition.setValue(position + 1);
});
}
}
I have a problem implementing Google signin with MVVM in Java.
here, in a normal way you will see this sample code from Google:
PROBLEM:
in your activity:
#Override
public void onCreate(Bundle savedInstanceState) {
/* Here is the Issue:
* Google Object is defined in View - Activity
* I would like to have Google Object defined in my ViewModel
*/
GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN).requestEmail().build();
mGoogleSignInClient = GoogleSignIn.getClient(this, gso);
}
// when Google Button CLicked
#Override
public void onClick(View v) { signIn(); }
private void signIn() {
/* Here is the Issue:
* I have to get this process done in View Model
* so view will not reference any Google Object
*/
Intent signInIntent = mGoogleSignInClient.getSignInIntent();
startActivityForResult(signInIntent, RC_SIGN_IN);
}
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// Below will be processed in ViewModel
GoogleSignInClient.getSignInIntent(...);
if (requestCode == RC_SIGN_IN) {
Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);
handleSignInResult(task);
}
}
QUESTIONS: *see comment
so I came out with Idea Below:
in Activity:
// when Google Button CLicked
#Override
public void onClick(View v) { viewModel.loginGoogle(); }
private void subscribeUi() {
// register startActivityForResult Event to ViewModel and set this activity as receiver...
// viewModel.startActivityForResultEvent.setEventReceiver(this Activity)
// How to do this?
}
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
// send the result to View Model
viewModel.onResultFromActivity(requestCode,resultCode,data);
// escallate to super
super.onActivityResult(requestCode, resultCode, data)
}
now in ViewModel:
public void viewModelOnCreate() {
// This is what i want: Google object defined in View Model
// but I dont know how to call startActivityForResult from here?
GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN).requestEmail().build();
mGoogleSignInClient = GoogleSignIn.getClient(getApplication(), gso);
}
// triggered when login button pressed
public void loginGoogle(){
// send Trigger startActivityForResult(getGoogleSignInIntent(), GOOGLE_SIGN_IN) this event should be catch later in my Activity
// How to do this?
// maybe something like:
// startActivityForResultEvent.sendEvent( ActivityNavigation.startActivityForResult startActivityForResult(getGoogleSignInIntent(), GOOGLE_SIGN_IN)
}
public void onResultFromActivity(int requestCode, int resultCode, Intent data){
// do whatever needed here after received result from Google
// for example:
if (requestCode == RC_SIGN_IN) {
Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);
handleSignInResult(task);
}
}
any Idea how to get this achieved?
been scratching my head to get this done...
thanks and Appreciate the help :)
}
I think you can do the following, it is not hold global reference to context so it will not leak
public void loginGoogle(Context context){
if(isSigningIn)
return
context.startActivityForResult(getGoogleSignInIntent(), GOOGLE_SIGN_IN)
isSigningIn = true;
}
You can use SingleLiveData to open new screen. See:
https://proandroiddev.com/livedata-with-single-events-2395dea972a8
You create class with all necessary parameters to start activity
In ViewModel you create this class with parameters you need
You create single live data field in your ViewModel and observe it from activity/fragment
You send this class with SingleLiveData
create class:
public Enum Screen {
LOGIN
}
in ViewModel:
...
private SingleLiveData<Screen> onOpenScreen = new SingleLiveData<Screen>()
public SingleLiveData<Screen> observeScreenOpen() {
return onOpenScreen
}
public void loginGoogle(){
onOpenScreen.value = Screen.LOGIN
}
...
in activity/fragment
viewModel.observeScreenOpen(this, new Observer<Screen> {screen->
if(screen == Screen.LOGIN) {
//start your activity here
}
})
This seems to be disencourage by the documentation and function that replaced startActivityForResult:
Register a request to start an activity for result, designated by the given contract. This creates a record in the registry associated with this caller, managing request code, as well as conversions to/from Intent under the hood. This must be called unconditionally, as part of initialization path, typically as a field initializer of an Activity or Fragment.
If the host of this fragment is an ActivityResultRegistryOwner the ActivityResultRegistry of the host will be used. Otherwise, this will use the registry of the Fragment's Activity.
Attention for the "This must be called unconditionally, as part of initialization path".
Also notice this IlliegalStateException message:
Fragment [this] is attempting to registerForActivityResult after being created. Fragments must call "registerForActivityResult() before they are created (i.e. initialization, "onAttach(), or onCreate()).
So my suggestion is to put the contract and registerForActivityResult() on your Activity or Fragment onCreate and whatever you will be doing with the result in a function in your view model / domain class, which is basically what you are already doing.
What I would do is register a callback in the ViewModel that is invoked that the Activity can react to. Then the ViewModel can own the bulk of the business logic but does not have to have a reference to the Activity or Context and the Activity can deal with the Activity-specific stuff of launching an Intent.
Example:
Callback Interface:
interface OnSignInStartedListener {
void onSignInStarted(GoogleSignInClient client);
}
ViewModel:
public class ViewModel {
private final OnSignInStartedListener mListener;
public ViewModel(OnSignInStartedListener listener) {
mListener = listener;
}
public void viewModelOnCreate() {
// This is what i want: Google object defined in View Model
// but I dont know how to call startActivityForResult from here?
GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN).requestEmail().build();
mGoogleSignInClient = GoogleSignIn.getClient(getApplication(), gso);
}
public void loginGoogle() {
// Invoke callback here to notify Activity
mListener.onSignInStarted(mGoogleSignInClient);
}
}
Activity:
protected void onCreate(Bundle savedInstanceState) {
...
mViewModel = new ViewModel(new OnSignInStartedListener() {
#Override
public void onSignInStarted(GoogleSignInClient client) {
startActivityForResult(client.getSignInIntent(), RC_SIGN_IN);
}
});
...
}
#Override
public void onClick(View v) {
// Invokes listener this activity created to start sign in flow
viewModel.loginGoogle();
}
Hope that helps!
I have MainActivity and on its onResume method I call pattern lock to create and confirm user identity. User visits and leave this MainActivity back and forth while active on the app as well as when phone is in sleep mode and user unlocks it. These both scenarios will call onRestart, onStart and onResume methods, but I only want to revoke the pattern in unlock scenario.
handlePattern() method needs a proper distinguishing to be called.
How to distinguish this when I call the handlePattern method ?
MainActivity.class
onCreate(){}
onResume(){
//help needed to know that user is just visiting activity in app back and forth
or came back after unlocking the screen.
if(isPatternCallRequired){
handlePattern()
}
}
In your onStop() method call you can check if the player is in sleep mode and cache the boolean.
PowerManager pm = (PowerManager)
_context.getSystemService(Context.POWER_SERVICE);
boolean isInSleepMode = !pm.isScreenOn();
Check for the build version
if( Build.VERSION.SDK_INT >= 20)
// use isInteractive()
else
// use isScreenOn()
in onRestart which will get called when you resume from sleep - based on the cached value you can show the pattern to unlock.
You may need to reset the cached value once you are done using it.
onResume may not be a right API for the call as it will be called even when your activity loads.
Edited answer based on your comment
You can try ActivityLifecycleCallbacks too like this,
First, Register your Application in your Application class.
public class StackApp extends Application {
private static final String TAG = StackApp.class.getSimpleName();
public static final String INTENT_ACTION_APP_STATE_CHANGE = "intent_action_app_state_change";
public static final String INTENT_DATA_IS_IN_BACKGROUND = "intent_data_is_in_background";
private static int mNumRunningActivities = 0;
private static AtomicBoolean mIsAppInForeground = new AtomicBoolean();
#Override
public void onCreate() {
super.onCreate();
if (Build.VERSION.SDK_INT >= 14) {
// registerActivityLifecycleCallbacks is supported only from the SDK version 14.
registerActivityLifecycleCallbacks(new Application.ActivityLifecycleCallbacks() {
#Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
}
#Override
public void onActivityStarted(Activity activity) {
mNumRunningActivities++;
if (mNumRunningActivities == 1) {
notifyAppState(false);
Log.i(TAG, "APP IN FOREGROUND");
}
}
#Override
public void onActivityResumed(Activity activity) {
}
#Override
public void onActivityPaused(Activity activity) {
}
#Override
public void onActivityStopped(Activity activity) {
mNumRunningActivities--;
if (mNumRunningActivities == 0) {
notifyAppState(true);
}
}
#Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
}
#Override
public void onActivityDestroyed(Activity activity) {
}
});
}
}
/**
* To notify App state whether its in ForeGround or in Background
*
* #param isInBackground
*/
private void notifyAppState(boolean isInBackground) {
if (isInBackground) {
mIsAppInForeground.set(false);
} else {
mIsAppInForeground.set(true);
}
sendAppStateChangeBroadcast(isInBackground);
}
public static boolean isInForeground() {
return mIsAppInForeground.get();
}
private void sendAppStateChangeBroadcast(boolean isInBackground) {
Log.i(TAG, "sendAppStateChangeBroadcast - isInBackground : " + isInBackground);
Intent intent = new Intent();
intent.setAction(INTENT_ACTION_APP_STATE_CHANGE);
intent.putExtra(INTENT_DATA_IS_IN_BACKGROUND, isInBackground);
LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
}
}
And register the broadcast and listen whether the App is going background or foreground like this Sample Activity example
public class SampleMyActivity extends AppCompatActivity {
private OnAppStateReceiver mAppStateReceiver;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sample_my);
mAppStateReceiver = new OnAppStateReceiver();
IntentFilter filter = new IntentFilter(StackApp.INTENT_ACTION_APP_STATE_CHANGE);
LocalBroadcastManager.getInstance(this).registerReceiver(mAppStateReceiver, filter);
}
#Override
protected void onDestroy() {
super.onDestroy();
if (mAppStateReceiver != null) {
LocalBroadcastManager.getInstance(this).unregisterReceiver(mAppStateReceiver);
}
}
private class OnAppStateReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (!TextUtils.isEmpty(action) && StackApp.INTENT_ACTION_APP_STATE_CHANGE.equalsIgnoreCase(action)) {
boolean isGoingBackground = intent.getBooleanExtra(StackApp.INTENT_DATA_IS_IN_BACKGROUND, false);
if (isGoingBackground) {
//Your app is not vissible to the use
} else {
// App is visible to the user.
}
}
}
}
}
Note: If you want to listen in Multiple Activity you can create a base
class and add the listener there and you can do the operation, In that
case you can reduce a lot of code.
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()
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.