Develop Reference

How can i make double press back to close my app

I have startActivity and HomeScreen activity. HomeScreen activity appears after startActivity. I want to implement double click back to close the application. I tried this code, but after the app is closed, it immediately reopens again or just returns to startActivity.
#Override
public void onBackPressed() {
if (doubleBackToExitPressedOnce) {
super.onBackPressed();
return;
}
this.doubleBackToExitPressedOnce = true;
Toast.makeText(this, "Нажмите ещё раз что бы закрыть приложение", Toast.LENGTH_SHORT).show();
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
doubleBackToExitPressedOnce = false;
}
}, 2000);
}

If this code is in some child activity (not in the main activity), then try replacing:
super.onBackPressed()
with:
finishAffinity()
Since according to the docs:
The default implementation simply finishes the current activity, but you can override this to do whatever you want.
calling super.onBackPressed() will finish current activity - not the whole application. And probably this is the source of Your bugs, but I cannot know for sure, since You haven't provided us with broader context - more code.
So, on the other hand finishAffinity() might be the solution for You. Docs say:
Finish this activity as well as all activities immediately below it in the current task that have the same affinity.
This should finish all the activities.

How to create a util that can be referenced multiple times in different activities

I have successfully implemented a custom Dialog box that appears when the user tries to leave an activity via a back button or by using onBackPressed(). They can simply cancel the dialog box or continue, and leave the activity. This function has been implemented in multiple activities, however its making my code a lot longer than it needs to be. I wanted to know how to create a util that can be referenced in different activities, without the need for the chunk of code to copy pasted multiple times. Please note that I am retrieving the dialog title and description from string.xml
This is my code:
Dialog customDialog;
Button button_one, button_two;
TextView dialog_title, dialog_description;
customDialog = new Dialog(this);
//Back button will close app
#Override
public void onBackPressed() {
customDialog.setContentView(R.layout.custom_dialog_box);
dialog_title = customDialog.findViewById(R.id.dialog_title);
dialog_title.setText(getString(R.string.leaving_activity_warning_title));
dialog_description = customDialog.findViewById(R.id.dialog_description); dialog_description.setText(getString(R.string.leaving_activity_warning_description));
button_one = customDialog.findViewById(R.id.button_one);
button_one.setText(getString(R.string.cancel));
button_two = customDialog.findViewById(R.id.button_two);
button_two.setText(getString(R.string.leave_anyway));
button_one.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
customDialog.dismiss();
}
});
button_two.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
customDialog.dismiss();
finish();
overridePendingTransition(R.anim.slide_in_left, R.anim.slide_out_right);
}
});
Objects.requireNonNull(customDialog.getWindow()).setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
customDialog.show();
}
UPDATE
Created a Java file called "DialogBoxMessage"
DialogBoxMessage Code:
class DialogBoxMessage {
private Dialog customDialog;
private TextView dialog_title, dialog_description;
private Button button_one, button_two;
//Custom Dialog Box Initialization
DialogBoxMessage(Button myButtonOne, TextView myDialogTitle, TextView myDialogDescription, Dialog myCustomDialog) {
customDialog = myCustomDialog;
button_one = myButtonOne;
button_two = myButtonOne;
dialog_title = myDialogTitle;
dialog_description = myDialogDescription;
}
void leaveActivity() {
customDialog.setContentView(R.layout.custom_dialog_box);
dialog_title = customDialog.findViewById(R.id.dialog_title);
dialog_title.setText(Resources.getSystem().getString(R.string.leaving_activity_warning_title));
dialog_description = customDialog.findViewById(R.id.dialog_description);
dialog_description.setText(Resources.getSystem().getString(R.string.leaving_activity_warning_description));
button_one = customDialog.findViewById(R.id.button_one);
button_one.setText(Resources.getSystem().getString(R.string.cancel));
button_two = customDialog.findViewById(R.id.button_two);
button_two.setText(Resources.getSystem().getString(R.string.leave_anyway));
button_one.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
customDialog.dismiss();
}
});
button_two.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
customDialog.dismiss();
}
});
Objects.requireNonNull(customDialog.getWindow()).setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
customDialog.show();
}
}
I input the following code in another activity
Other activity code:
//Reusable exit dialog message
DialogBoxMessage dialogBoxMessage;
//Back button will close app
#Override
public void onBackPressed() {
dialogBoxMessage.leaveActivity();
finish();
}
But it doesn't seem to work, I think there are a lot of issues... please help :(

I assume customDialog is a seperate class you wrote - therefore i would suggest you put main information like contentview, title, message or type in the constructor when you initialize ur Dialog.
For your onClick Method I suggest you create an Interface to handle Button Clicks in your
customDialog class.

This could be implemented as a static method in a utilities class. The method would require 'this' as a parameter, which contains the activity context. The method should return the result of the button press. The activity can use this response to determine if finish() should be called or not.
UPDATE
I had suggested a simple static method, but you've gone down the object-oriented route. That's fine.
However, your constructor requires passing in several views, which wouldn't appear to achieve the code efficiency you are after.
Your constructor should just require the Activity context; everything else is encapsulated in your new class.
In each Activity's onBackPressed method you will need to create the object with
dialogBoxMessage = new DialogBoxMessage(this);
before you can call any of that object's methods.

Have to press the back button twice to get to previous activity?

I am simply trying to click back and navigate to my previous activity. My flow is this: I go to news_feed activity -> Comments activity -> User Profile activity -> click back (Go to Comments activity) -> click back (This does nothing for some reason) -> Click back (Go back to news_feed activity). I'm not sure why I have to click back twice when I try to go from Comments activity back to news_feed activity. If I go from news_feed activity -> Comments -> press back (Go to news_feed activity) this works perfectly. Here is my code:
news_feed.java:
#Override
public void onBackPressed() {
super.onBackPressed();
Intent startMain = new Intent(Intent.ACTION_MAIN);
startMain.addCategory(Intent.CATEGORY_HOME);
startMain.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(startMain);
}
Comments.java:
#Override
public void onBackPressed() {
super.onBackPressed();
this.finish();
}
UserProfile.java:
#Override
public void onBackPressed() {
super.onBackPressed();
Intent intent = new Intent(UserProfile.this, Comments.class);
Bundle bundle = new Bundle();
bundle.putString("postId", postId);
bundle.putString("posterUserId", posterUserId);
bundle.putString("posterName", posterName);
bundle.putString("postStatus", postStatus);
bundle.putString("postTimeStamp", postTimeStamp);
bundle.putString("postTitle", postTitle);
intent.putExtras(bundle);
startActivity(intent);
finish();
}
I don't think navigating to these activities would change anything, but I can include the intents that I used to navigate to these activities also if necessary. Otherwise I just included the onBackPressed code that I had for these activities. Any ideas why this might cause a problem? Any help would be appreciated. Thanks.

In your UserProfile class, in onBackPressed() method, you are starting the Comments class again. Why do you have to do this?
What is happening is, you are starting a new Comments activity onBackPressed() of the USerProfile class, so there are two instances of Comments Activity. So you feel you are pressing back btn twice.
If you have to pass data back to Comments from UserProfile class, then make use of setResult() method.
This will be of help
How to pass data from 2nd activity to 1st activity when pressed back? - android
Sending data back to the Main Activity in android

I you want to send back the result to previous activity the start activity by using
startActivityForResult()
insead of
startActivity()
and don't override
onBackPressed()

You can try something like this:
private boolean clicked;
#Override
public void onBackPressed() {
if (!clicked) { // if it was not clicked before, change the value of clicked to true and do nothing directly return, if clicked again, then it will be finish the activity.
clicked=true;
return;
}
super.onBackPressed();
}
And if you are going to use the time, then you can do like this:
private long lastClicked;
#Override
public void onBackPressed() {
if (System.currentTimeMillis() - lastClicked < 1000) { // within one second
super.onBackPressed();
}
lastClicked = System.currentTimeMillis();
}

You don't need to override onBackPressed() if all you're going to do is call startActivity() and finish() in the current activity. The Android backstack will handle both of those for you. Moreover, in your UserProfile.java you are passing data to previous activity. For this, you should use startActvityForResult() in the Comments activity (i.e the previous activity) instead of startActivity().
To learn more about startActvityForResult() visit: https://developer.android.com/training/basics/intents/result.html

public void onBackPressed() {
if (this.lastBackPressTime < System.currentTimeMillis() - 2000) {
this.lastBackPressTime = System.currentTimeMillis();
} else {
//super.onBackPressed(); for exit
//INTENT HERE TO YOUR SECOND ACTIVITY like below
Intent intent=new Intent(A.this,B.class);
startActivirty(intent);
}
}
Create a global variable
private long lastBackPressTime = 0;
Hope this will help you,Let me know..

Method unnecessarily getting called?

I have a BaseActivity that gets extended by every other activity. The thing is, I have the music muted whenever the user leaves (onPause) the activity. I also stop listening for telephone calls. The problem is, onPause is getting called whenever the user switches between activities, meaning the app is unnecessarily muting and stopping telephonymanager, even though it should only be muting and stopping telephonymanager if the user were to leave the app.:
#Override
protected void onPause() {
Log.v(TAG, "IN onPause!");
// unregister phone listener to telephony manager
tManager.listen(phoneStateListener, PhoneStateListener.LISTEN_NONE);
mute();
super.onPause();
}
Now say I switch between public class myClass extends BaseActivity and switch to public class myOtherClass extends BaseActivity. This switch is unnecessarily executing onPause, even though I only want onPause to be called when the user leaves the app. What should I do?
Thanks for the expert advice,
Rich

From my understanding you are muting your music playing in onPause of BaseActivity, instead of that write it inside your Music play activity
Ex :
public class BaseActivity extends AppCompatActivity{
#Override
public void onPause(){
//do things that common for all activities
}
}
public void MusicPlayActivity extends AppCompatActivity{
#Override
public void onPause(){
music.mute()
}
}
This will work
UPDATE
There are few ways to detect whether your application is running in the background, but only one of them is completely reliable:
Track visibility of your application by yourself using Activity.onPause, Activity.onResume methods. Store "visibility" status in some other class.
Example
: Implement custom Application class (note the isActivityVisible() static method):
public class MyApplication extends Application {
public static boolean isActivityVisible() {
return activityVisible;
}
public static void activityResumed() {
activityVisible = true;
}
public static void activityPaused() {
activityVisible = false;
}
private static boolean activityVisible;
}
Register your application class in AndroidManifest.xml:
<application
android:name="your.app.package.MyApplication"
android:icon="#drawable/icon"
android:label="#string/app_name" >
Add onPause and onResume to every Activity in the project (you may create a common ancestor for your Activities if you'd like to, but if your activity is already extended from MapActivity/ListActivity etc. you still need to write the following by hand):
#Override
protected void onResume() {
super.onResume();
MyApplication.activityResumed();
}
#Override
protected void onPause() {
super.onPause();
MyApplication.activityPaused();
}
ActivityLifecycleCallbacks were added in API level 14 (Android 4.0). You can use them to track whether an activity of your application is currently visible to the user. Check Cornstalks' answer below for the details.

From your comments you only want to stop the music when the last Activity of your application is exiting. Overriding the finish() method of your BaseActivity like this should accomplish what you want:
#Override
public void finish() {
super.finish();
if (isTaskRoot()) {
// This is the last Activity in the stack so mute your music here...
}
}
Actually you probably want onDestroy() or onStop() as I'm not sure finish() executes unless you call it but the idea is the same:
#Override
protected void onDestroy() {
super.onDestroy();
if (isTaskRoot()) {
// This is the last Activity in the stack so mute your music here...
}
}
Here's info on isTaskRoot():
Return whether this activity is the root of a task. The root is the first activity in a task.
Returns
True if this is the root activity, else false.

OnCancelListener is not called in DialogFragment

I have a simple AlertDialog that displays a list of some items and upon clicking one of them, the clicked item is passed back to the enclosing Activity. I also want to perform some default handling when the user cancels the dialog (using the back button) - more specifically, I want to pass an empty string to the activity in such case.
However, if I put the dialog in a DialogFragment (from the compatibility package), the OnCancelListener is not called when I close the dialog with the back button. What am I doing wrong?
public class SelectItemDialog extends DialogFragment {
public interface Callback {
void onItemSelected(String string);
}
private static final String ARG_ITEMS = "items";
private Callback callback;
public static SelectItemDialog fromItems(Collection<String> items) {
SelectItemDialog fragment = new SelectItemDialog();
fragment.setArguments(newArguments(items));
return fragment;
}
private static Bundle newArguments(Collection<String> items) {
Bundle arguments = new Bundle();
arguments.putStringArray(ARG_ITEMS, items.toArray(new String[items.size()]));
return arguments;
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
callback = (Callback) activity;
}
#Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
final String[] items = getArguments().getStringArray(ARG_ITEMS);
return new AlertDialog.Builder(getActivity())
.setTitle(R.string.dialog_select_email_title)
.setItems(items, new OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
callback.onItemSelected(items[which]);
}
})
.setOnCancelListener(new OnCancelListener() {
#Override
public void onCancel(DialogInterface dialog) {
// this code is not executed
callback.onItemSelected("");
throw new RuntimeException("dialog cancelled");
}
})
.create();
}
}

It might have to do with the fact that there is no explicit call to cancel() from your code.
The OnCancelListener documentation says:
This will only be called when the dialog is canceled
Which probably needs an explicit cancel() call.
Either make a positive/negative button with a OnClickListener that calls DialogInterface#cancel() or use a OnDismissListener() with an extra check to see if a list item was clicked.
Also, to listen for a back keypress and cancel the dialog, you can set up an OnKeyListener, like outlined in this SO answer
Also, once you have the Dialog set up, it would also be a good idea to use Dialog#setCanceledOnTouchOutside() in case the the user taps outside the Dialog.
Edit: The below part is the easy way to handle cancel events in a DialogFragment.
Since you are using a DialogFragment, this class has a very handy method, DialogFragment#onCancel() which gets called when the DialogFragment is cancelled. Do your logic in there.
DialogFragments are more complex, with a slightly different lifecycle than normal dialogs. Therefore, first check the documentation if you have a certain Dialog-based approach that you are trying to port to a DialogFragment, some methods may exist that allow your new implementation to function properly!

If you are using DialogFragment and want to listen back button then use this -
this.getDialog().setOnKeyListener(new Dialog.OnKeyListener() {
#Override
public boolean onKey(DialogInterface dialog, int keyCode,
KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
if (****) {
your logic
}
return true;
}
return false;
}
});

Note: DialogFragment own the Dialog.setOnCancelListener and Dialog.setOnDismissListener callbacks. You must not set them yourself.
To find out about these events, override onCancel(DialogInterface) and onDismiss(DialogInterface).
public class SelectItemDialog extends DialogFragment {
#Override
public void onDismiss(DialogInterface dialog) {
super.onDismiss(dialog);
//your code hear
dialog.cancel();
}
}
And you should remove .setOnCancelListener()

Actually if you want to use DialogFragment, you can never add OnCancelListener or OnDismissListener to it, since the Dialog Fragment owns callbacks to these methods!
You have 3 options here:
1- go with regular dialogs.2- set your dialog fragment to cancellable(false) and add a cancel button to the dialog.3- check #Nikhil Pingle answer.
this is from the documentation of the Dialog Fragment
* <p><em>Note: DialogFragment own the {#link Dialog#setOnCancelListener
* Dialog.setOnCancelListener} and {#link Dialog#setOnDismissListener
* Dialog.setOnDismissListener} callbacks. You must not set them yourself.</em>
* To find out about these events, override {#link #onCancel(DialogInterface)}
* and {#link #onDismiss(DialogInterface)}.</p>

Cancel Listener or Dismiss listener in DialogFragment can achieve by onDismiss
DialogFragment newFragment = new DatePickerFragment();
newFragment.show(getFragmentManager(), "datePicker");
newFragment.onDismiss(new DialogInterface(){
#Override
public void cancel() {
// TODO Auto-generated method stub
}
#Override
public void dismiss() {
// TODO Auto-generated method stub
}
});