Develop Reference

How to set up a custom listener in a custom dialog for android?

I'm currently having trouble setting up my custom listener. I just want to pass a string from my dialog to my fragment (where I set up the dialog). I was trying to follow this tutorial: https://www.youtube.com/watch?v=ARezg1D9Zd0.
At minute 10:38, he sets up the listener.
This only problem is that in this, he uses DialogFragment, but I'm extending dialog and I don't know how to attach the context to the listener.
I've tried to set it up in onAttachedToWindow() and in the dialog constructor but it crashes.
What should I actually do?
I'd also appreciate it if someone could explain what the difference is between:
onAttachedToWindow() vs. onAttach(Context context).
Thanks!
MY CUSTOM DIALOG BOX:
public class NewListDialog extends Dialog implements View.OnClickListener {
private Activity c;
private TextInputLayout textInputLayout;
private TextInputEditText editText;
private LinearLayout dialog_root_view;
private Animation fade_out;
private String list_name;
private NewListDialogListener listener;
NewListDialog(Activity a) {
super(a);
this.c = a;
//ANOTHER ATTEMPT TO ATTACH CONTEXT TO LISTENER
//listener = (NewListDialogListener) a.getApplicationContext();
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.new_list_dialog);
MaterialButton cancel = findViewById(R.id.dialog_new_list_cancel_button);
MaterialButton create = findViewById(R.id.dialog_new_list_create_button);
textInputLayout = findViewById(R.id.dialog_text_input_layout);
editText = findViewById(R.id.dialog_edit_text);
dialog_root_view = findViewById(R.id.dialog_root);
fade_out = AnimationUtils.loadAnimation(c, R.anim.fade_out_dialog);
editText.setOnKeyListener(new View.OnKeyListener() {
#Override
public boolean onKey(View view, int i, KeyEvent keyEvent) {
if (isTextValid(editText.getText())) {
textInputLayout.setError(null);
return true;
}
return false;
}
});
cancel.setOnClickListener(this);
create.setOnClickListener(this);
}
#Override
public void onClick(View view) {
switch (view.getId()) {
//Cancel Button
case R.id.dialog_new_list_cancel_button:
dialog_root_view.startAnimation(fade_out);
final Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
dismiss();
}
}, 200);
break;
//Create Button
case R.id.dialog_new_list_create_button:
if (!isTextValid(editText.getText())) {
textInputLayout.setError(c.getString(R.string.dialog_error));
} else {
textInputLayout.setError(null);
//record input string
list_name = editText.getText().toString();
//send information to parent activity
//What to put here?
listener.createListName(list_name);
dismiss();
}
break;
default:
break;
}
}
private boolean isTextValid(#Nullable Editable text) {
return text != null && text.length() > 0;
}
//ATTEMPT TO ATTACH CONTEXT TO LISTENER
#Override
public void onAttachedToWindow() {
super.onAttachedToWindow();
try {
listener = (NewListDialogListener) c.getBaseContext();
} catch (ClassCastException e) {
throw new ClassCastException(c.getBaseContext().toString() + "must implement ExampleDialogListener");
}
}
public interface NewListDialogListener {
void createListName(String listname);
}
}

In case you define a custom dialog then you can declare a method to allow other components call it or listen events on this dialog. Add this method to you custom dialog.
public void setNewListDialogListener(NewListDialogListener listener){
this.listener = listener;
}
NewListDialog.java
public class NewListDialog extends Dialog implements View.OnClickListener {
private Activity c;
private TextInputLayout textInputLayout;
private TextInputEditText editText;
private LinearLayout dialog_root_view;
private Animation fade_out;
private String list_name;
private NewListDialogListener listener;
NewListDialog(Activity a) {
super(a);
this.c = a;
}
public void setNewListDialogListener(NewListDialogListener listener) {
this.listener = listener;
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.new_list_dialog);
MaterialButton cancel = findViewById(R.id.dialog_new_list_cancel_button);
MaterialButton create = findViewById(R.id.dialog_new_list_create_button);
textInputLayout = findViewById(R.id.dialog_text_input_layout);
editText = findViewById(R.id.dialog_edit_text);
dialog_root_view = findViewById(R.id.dialog_root);
fade_out = AnimationUtils.loadAnimation(c, R.anim.fade_out_dialog);
editText.setOnKeyListener(new View.OnKeyListener() {
#Override
public boolean onKey(View view, int i, KeyEvent keyEvent) {
if (isTextValid(editText.getText())) {
textInputLayout.setError(null);
return true;
}
return false;
}
});
cancel.setOnClickListener(this);
create.setOnClickListener(this);
}
#Override
public void onClick(View view) {
switch (view.getId()) {
//Cancel Button
case R.id.dialog_new_list_cancel_button:
dialog_root_view.startAnimation(fade_out);
final Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
dismiss();
}
}, 200);
break;
//Create Button
case R.id.dialog_new_list_create_button:
if (!isTextValid(editText.getText())) {
textInputLayout.setError(c.getString(R.string.dialog_error));
} else {
textInputLayout.setError(null);
//record input string
list_name = editText.getText().toString();
//send information to parent activity
//What to put here?
if (listener != null) {
listener.createListName(list_name);
}
dismiss();
}
break;
default:
break;
}
}
private boolean isTextValid(#Nullable Editable text) {
return text != null && text.length() > 0;
}
public interface NewListDialogListener {
void createListName(String listname);
}
}
In other components such as an activity which must implements NewListDialogListener.
NewListDialog dialog = new NewListDialog(this);
dialog.setNewListDialogListener(this);
If you don't want the activity implements NewListDialogListener then you can pass a listener instead.
NewListDialog dialog = new NewListDialog(this);
dialog.setNewListDialogListener(new NewListDialog.NewListDialogListener() {
#Override
public void createListName(String listname) {
// TODO: Your code here
}
});

In android Fragments and Activity has lifecycles. Fragments are hosted inside Activity and get the context of host activity via onattach method.
On the other hand Dialog is extended from Object (God class) without any lifecycle and should be treaded as an object.
If your activity is implementing NewListDialogListener then you can do
listener = (NewListDialogListener) a;
onAttachedToWindow : mean the dialog will be drawn on screen soon
and
getApplicationContext() will give you the context object of the application (one per app) which is surely not related with your listener and hence won't work
Reference :
Android DialogFragment vs Dialog
Difference between getContext() , getApplicationContext() , getBaseContext() and “this”

You can use RxAndroid instead of using listener, in this situation I use RxAndroid to get data from dialogs to activities or fragments.
Just need to create a PublishSubject and get the observed data. on activity or fragment :
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
PublishSubject<String > objectPublishSubject = PublishSubject.create();
objectPublishSubject.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.newThread())
.subscribe(this::onNext);
CustomDialog customDialog = new CustomDialog(this, objectPublishSubject);
customDialog.show();
}
private void onNext(String data) {
Log.i("DIALOG_DATA", data);
}
and you can create dialog like this :
public class CustomDialog extends Dialog implements View.OnClickListener {
private PublishSubject<String> subject;
public CustomDialog(#NonNull Context context, PublishSubject<String> subject) {
super(context);
this.subject = subject;
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.custom_dialog);
findViewById(R.id.button).setOnClickListener(this);
}
#Override
public void onClick(View v) {
subject.onNext("Data");
dismiss();
}

how to call an intent from a different class

I am trying to call an intent from a handler and I don't know how to do it. I have tried many different ways but it does't seem to be working. I want to start the PrimeNumbersActivity when the progress dialog reaches its max.
public class MyHandler extends Handler {
ProgressDialog progressDialog;
Context context;
public MyHandler(ProgressDialog progressDialog) {
this.progressDialog = progressDialog;
}
public MyHandler(Context context){
this.context = context;
}
#Override
public void handleMessage(Message msg) {
findPrimeNumber(Integer.parseInt(msg.obj.toString()));
}
public void findPrimeNumber(int number){
ArrayList<Integer> primeNumbers = new ArrayList<>();
boolean isPrimeNumber;
PrimeNumbers primeNumbers1 = new PrimeNumbers();
for(int i = 2; i <= number; i++){
isPrimeNumber = true;
for(int j = 1; j <= i; j++){
try {
sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
if(j != 1 && j != i){
if(i%j == 0){
isPrimeNumber = false;
break;
}
}
}
if(isPrimeNumber){
primeNumbers.add(i);
primeNumbers1.primeNumbers.add(i);
}
progressDialog.setProgress(i*100/number);
if(progressDialog.getProgress() == progressDialog.getMax()){
progressDialog.dismiss();
Intent intent = new Intent(context.getApplicationContext(),PrimeNumbersActivity.class);
context.startActivity(intent);
}
}
for (int i :
primeNumbers) {
Log.d(TAG, i + "");
}
}
}
the PrimeNumbersActivity
public class PrimeNumbersActivity extends AppCompatActivity {
private PrimeNumbers primeNumbers = new PrimeNumbers();
private ListView listView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_prime_numbers);
listView = findViewById(R.id.listView);
if(primeNumbers.primeNumbers.isEmpty()){
Toast.makeText(getApplicationContext(),"Pas de nombres premiers",Toast.LENGTH_SHORT).show();
}else{
ArrayAdapter<Integer> arrayAdapter = new ArrayAdapter<Integer>(getApplicationContext(),android.R.layout.simple_list_item_1,primeNumbers.primeNumbers);
listView.setAdapter(arrayAdapter);
}
}
}
MainActivity
public class MainActivity extends AppCompatActivity {
public static final int number = 20;
public Button button;
public EditText editText;
public ProgressDialog progressDialog;
public AlertDialog.Builder alertDialog;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
progressDialog = new ProgressDialog(MainActivity.this);
progressDialog.setMax(100);
progressDialog.setMessage("Please wait...");
progressDialog.setTitle("Finding prime numbers");
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
final MyThread thread = new MyThread(progressDialog);
thread.setName("MyThread");
thread.start();
button = (Button) findViewById(R.id.afficherNombrePremier);
editText = (EditText) findViewById(R.id.editText);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(editText.getText().toString().isEmpty()){
alertDialog = new AlertDialog.Builder(MainActivity.this);
alertDialog.setTitle("Warning");
alertDialog.setMessage("Veuillez saisir un nombre entier dans la zone de texte");
alertDialog.show();
}
else{
progressDialog.show();
Message message = Message.obtain();
message.obj = editText.getText().toString();
thread.mHandler.sendMessage(message);
}
}
});
}
}
Error:
04-24 00:45:15.457 4625-4712/com.example.mohammed.tdservicesex1 E/AndroidRuntime: FATAL EXCEPTION: MyThread
Process: com.example.mohammed.tdservicesex1, PID: 4625
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference
at com.example.mohammed.tdservicesex1.MyHandler.findPrimeNumber(MyHandler.java:65)
at com.example.mohammed.tdservicesex1.MyHandler.handleMessage(MyHandler.java:31)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at com.example.mohammed.tdservicesex1.MyThread.run(MyThread.java:22)
Thread:
public class MyThread extends Thread {
private static final String TAG = MyThread.class.getSimpleName();
public MyHandler mHandler;
ProgressDialog progressDialog;
public MyThread(ProgressDialog progressDialog) {
this.progressDialog = progressDialog;
}
#Override
public void run() {
Looper.prepare();
mHandler = new MyHandler(progressDialog);
Looper.loop();
}
}

The error is happened because you haven't set any context with your constructor in your MyHandler class. Your constructors is like the following:
public class MyHandler extends Handler {
...
public MyHandler(ProgressDialog progressDialog) {
this.progressDialog = progressDialog;
}
public MyHandler(Context context){
this.context = context;
}
...
}
you can see that you have 2 different constructors. In your code, you're only using the first constructor, you never assign the context with your second constructor. This is a common error when you're using multiple constructor for a class.
To solve the problem, you need to change your constructor so that it needs two parameters: ProgressDialog and Context. Change the constructor to something like this:
public class MyHandler extends Handler {
...
public MyHandler(ProgressDialog progressDialog, Context context) {
this.progressDialog = progressDialog;
this.context = context;
}
...
}

I believe you cannot start an activity using the application context (in a straightforward manner). You either have to
Use activity context
Use application context but add this flag FLAG_ACTIVITY_NEW_TASK
Be warned that FLAG_ACTIVITYNEW_TASK will start a new task in the history stack
Try something like this:
Intent intent = new Intent(context.getApplicationContext(),PrimeNumbersActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(intent);

Make sure you declared PrimeNumbersActivity in Android Manifest
This should work:
Intent intent = new Intent(context,PrimeNumbersActivity.class);
context.startActivity(intent);
If #2 does not work. It means this condition is always false:
if(progressDialog.getProgress() == progressDialog.getMax())

Android: How to finish an activity by an ImageView which belongs to the activity in an another class

I want to finish an activity by an image, and here is what I did:
there's an ImageView in the layout [activity_login.xml] .
/**
* the activity that I want to destroy
*/
public class LoginActivity extends Activity {
public static LoginActivity activityInstance;
private ImageView imgBtnBack;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
// for closing this activity by an another class
activityInstance = this;
// add event listener
imgBtnBack = (ImageView) findViewById(R.id.img_btn_back);
imgBtnBack.setOnClickListener(new LoginActivityListener());
}
#Override
protected void onDestroy() {
super.onDestroy();
}
}
/**
* the event handler of LoginActivity
*/
public class LoginActivityListener implements View.OnClickListener{
private Context context;
#Override
public void onClick(View view) {
context = view.getContext();
int id = view.getId();
switch (id) {
case R.id.img_btn_back: // close the activity by an image
LoginActivity.activityInstance.finish();
default:
break;
}
}
}
And I don't know if it was good by the way I did.
can anyone find and tell me a better way to make this work.

Add below code in your onCreate method
imgBtnBack = (ImageView) findViewById(R.id.img_btn_back);
imgBtnBack .setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
finish();
}
});

onClickListener not working in my activity

My layout has 13 TextViews which on click changes the ListView Items.
Here is my activity:
public class ExampleActivity extends ListActivity implements
OnClickListener {
private String[] sa = new String[100];
private ListView lv;
private Context context = this;
private ArrayAdapter adapter;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
new LongOperation().execute("1");
lv = getListView();
}
private class LongOperation extends AsyncTask<String, Void, String> {
private ProgressDialog dialog = new ProgressDialog(
ExampleActivity.this);
#Override
protected String doInBackground(String... params) {
int i = Integer.parseInt(params[0]);
for (int n = 0; n < 100; n++) {
if (i != 5 && i != 10) {
sa[n] = "Item" + i;
} else {
}
}
return params[0];
}
#Override
protected void onPostExecute(String result) {
adapter = new ArrayAdapter<Object>(context,
android.R.layout.simple_list_item_1, sa);
lv.setAdapter(adapter);
this.dialog.dismiss();
}
#Override
protected void onPreExecute() {
this.dialog.setMessage("Please wait");
this.dialog.show();
}
#Override
protected void onProgressUpdate(Void... values) {
}
}
public void onClick(View v) {
Log.d("onClick", v.getId() + "**");
int id = v.getId();
switch (id) {
case R.id.tv1: {
new LongOperation().execute("1");
}
case R.id.tv2: {
new LongOperation().execute("2");
}
case R.id.tv3: {
new LongOperation().execute("3");
}
case R.id.tv4: {
new LongOperation().execute("4");
}
case R.id.tv5: {
new LongOperation().execute("5");
}
case R.id.tv6: {
new LongOperation().execute("6");
}
case R.id.tv7: {
new LongOperation().execute("7");
}
case R.id.tv8: {
new LongOperation().execute("8");
}
case R.id.tv9: {
new LongOperation().execute("9");
}
case R.id.tv10: {
new LongOperation().execute("10");
}
case R.id.tv11: {
new LongOperation().execute("11");
}
case R.id.tv12: {
new LongOperation().execute("12");
}
case R.id.tv13: {
new LongOperation().execute("13");
}
}
}
}
the listView is populated as item1 when i launch the app. but when i click on any of the TextViews, the onClick method is not triggered. i checked it using a Log.
Thank You.

Because you are not registering onClickListener with your TextViews hence your TextViews are not getting Clicked event.
For this you have to do something like,
onCreate()
{
TextView tv1 = (TextVIew)findViewById(R.id.tv1);
tv1.setOnClickListener(this);
Better Solution:
In your Activity's xml Layout File,
in your all TextView put attribute android:onClick="textClick"
Now remove onClickListener from your Activity and just write
public void textClick(View TextView)
in your activity. Then you don't have to register onClicklistener for all TextView. Android does itself for you..

This is a sample program provided when you use implements OnClickListener
public class ExampleActivity extends Activity implements OnClickListener {
protected void onCreate(Bundle savedValues) {
Button button = (Button)findViewById(R.id.corky);
button.setOnClickListener(this); // have a look on this line. registering.
}
// Implement the OnClickListener callback
public void onClick(View v) {
// do something when the button is clicked
}
}

this happens because you not using the setOnClickListener() for your TextViews

Add this static function in your activity class, This work for me in my MainActivity.java
public class MainActivity extends AppCompatActivity {
static {
AppCompatDelegate.setCompatVectorFromResourcesEnabled(true);
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}

AsyncTask : passing value to an Activity (onCreate method )

Update1
activity:
public Integer _number = 0;
#Override
public void onCreate(Bundle savedInstanceState) {
if (_number >0)
{
Log.d("onSuccessfulExecute", ""+_number);
}
else
{
Log.d("onSuccessfulExecute", "nope empty songs lists");
}
}
public int onSuccessfulExecute(int numberOfSongList) {
_number = numberOfSongList;
if (numberOfSongList >0)
{
Log.d("onSuccessfulExecute", ""+numberOfSongList);
}
else
{
Log.d("onSuccessfulExecute", "nope empty songs lists");
}
return numberOfSongList;
}
end Update1
UPDATE: AsynchTask has its own external class.
How to pass an value from AsyncTask onPostExecute()... to activity
my code does returning value from onPostExecute() and updating on UI but i am looking for a way to set the activity variable (NumberOfSongList) coming from AsynchTask.
AsyncTask class:
#Override
public void onPostExecute(asynctask.Payload payload)
{
AsyncTemplateActivity app = (AsyncTemplateActivity) payload.data[0];
//the below code DOES UPDATE the UI textView control
int answer = ((Integer) payload.result).intValue();
app.taskStatus.setText("Success: answer = "+answer);
//PROBLEM:
//i am trying to populate the value to an variable but does not seems like the way i am doing:
app.NumberOfSongList = payload.answer;
..............
..............
}
Activity:
public Integer NumberOfSongList;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//Several UI Code
new ConnectingTask().execute();
Log.d("onCreate", ""+NumberOfSongList);
}

What about using a setter method? e.g.
private int _number;
public int setNumber(int number) {
_number = number;
}
UPDATE:
Please look at this code. This will do what you're trying to accomplish.
Activity class
public class TestActivity extends Activity {
public int Number;
#Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.test);
Button btnDisplay = (Button) findViewById(R.id.btnDisplay);
btnDisplay.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Toast toast = Toast.makeText(v.getContext(), "Generated number: " + String.valueOf(Number), Toast.LENGTH_LONG);
toast.show();
}
});
new TestTask(this).execute();
}
}
AsyncTask class
public class TestTask extends AsyncTask<Void, Void, Integer> {
private final Context _context;
private final String TAG = "TestTask";
private final Random _rnd;
public TestTask(Context context){
_context = context;
_rnd = new Random();
}
#Override
protected void onPreExecute() {
//TODO: Do task init.
super.onPreExecute();
}
#Override
protected Integer doInBackground(Void... params) {
//Simulate a long-running procedure.
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
Log.e(TAG, e.getMessage());
}
return _rnd.nextInt();
}
#Override
protected void onPostExecute(Integer result) {
TestActivity test = (TestActivity) _context;
test.Number = result;
super.onPostExecute(result);
}
}

Just a word of caution: Be very careful when attempting to hold a reference to an Activity instance in an AsyncTask - I found this out the hard way :). If the user happens to rotate the device while your background task is still running, your activity will be destroyed and recreated thus invalidating the reference being to the Activity.

Create a listener.
Make a new class file. Called it something like MyAsyncListener and make it look like this:
public interface MyAsyncListener() {
onSuccessfulExecute(int numberOfSongList);
}
Make your activity implement MyAsyncListener, ie,
public class myActivity extends Activity implements MyAsyncListener {
Add the listener to the constructor for your AsyncTask and set it to a global var in the Async class. Then call the listener's method in onPostExecute and pass the data.
public class MyCustomAsync extends AsyncTask<Void,Void,Void> {
MyAsyncListener mal;
public MyCustomAsync(MyAsyncListener listener) {
this.mal = listener;
}
#Override
public void onPostExecute(asynctask.Payload payload) {
\\update UI
mal.onSuccessfulExecute(int numberOfSongList);
}
}
Now, whenever your AsyncTask is done, it will call the method onSuccessfulExecute in your Activity class which should look like:
#Override
public void onSuccessfulExecute(int numberOfSongList) {
\\do whatever
}
Good luck.