Press back button twice to exit the app with some condition

Question

All I want is to exit the application only when back stack is empty.

One section of my app contains a gallery,in which, when a picture is clicked, a fragment showing the full screen image is opened. When back button is pressed in this full screen image, I want to go back to the gallery fragment. I did this by adding the fragment to back stack.

But in other parts of the application, when back button is pressed, I want to show a toast "Please click BACK again to exit". And when the back button is pressed again, the app closes. How can I do this?

This is what I have done so far:

 boolean doubleBackToExitPressedOnce = false;
@Override
public void onBackPressed() {
    if (getFragmentManager().getBackStackEntryCount() > 0 ){
       getFragmentManager().popBackStack();
    } else {

        if (doubleBackToExitPressedOnce) {
            super.onBackPressed();
            return;
        }

        this.doubleBackToExitPressedOnce = true;
        commonTasks.ShowStringMessage("Please click BACK again to exit");

        new Handler().postDelayed(new Runnable() {

            @Override
            public void run() {
                doubleBackToExitPressedOnce=false;
            }
        }, 2000);

       //super.onBackPressed();
    }
}

Obviously, it didn't work.

please confirm if you are you adding your fragments to backstack using getFragmentManager() or getSupportFragmentManager() — Nitesh, Sep 26 '16 at 12:35
your code is looking fine to me.. can you please tell whats happening when your are pressing the back button? — Nitesh, Sep 26 '16 at 12:39
@Nitesh: Instead of just going back to gallery fragment when I click back button from fullimage fragment, I get the toast message: "Please click BACK again to exit". I have to tap back button twice from full image fragment to go back to the gallery. — Tom Alex, Sep 26 '16 at 12:49

score 0 · Answer 1 · edited May 23 '17 at 10:27

0

You can try using getSupportFragmentManager()

It has a method which returns array of all the fragments it is containing and you can put the check for its size as following

boolean doubleBackToExitPressedOnce = false;
@Override
public void onBackPressed() {
if (getSupportFragmentManager().getFragments().size() > 0 ){
   getSupportFragmentManager().popBackStack();
} else {

    if (doubleBackToExitPressedOnce) {
        super.onBackPressed();
        return;
    }

    this.doubleBackToExitPressedOnce = true;
    commonTasks.ShowStringMessage("Please click BACK again to exit");

    new Handler().postDelayed(new Runnable() {

        @Override
        public void run() {
            doubleBackToExitPressedOnce=false;
        }
    }, 2000);

   //super.onBackPressed();
}

}

P.S: you also need to change getSupportFragmentManager() while fragment transection.

Also reffer this link Why FragmentManager's getBackStackEntryCount() return zero?

edited May 23 '17 at 10:27

Community

1
1

answered Sep 26 '16 at 12:48

Nitesh

3,868
1
20
26

Now its not even showing the toast message. The app closes on the first back button press – Tom Alex Sep 26 '16 at 12:59
sry my bad .. updating my answer – Nitesh Sep 26 '16 at 12:59
Now the app isnt exiting at all when I click the back button – Tom Alex Sep 26 '16 at 13:11
Have you got a better solution? – Tom Alex Sep 26 '16 at 13:35
this one is working at my end. so Debugging your code is better option for you. – Nitesh Sep 26 '16 at 13:38
I have found out that the control gets in the else section every time even if the if condition(i.e if the back stack is not empty) is true. Do you have any idea why this is happening? – Tom Alex Sep 26 '16 at 13:42

score 0 · Answer 2 · answered Sep 26 '16 at 13:05

You can try something diff. Add Exit code in your Activity's onBackPressed Method, and whenever you get the onBackPressed trigger Just check that is your Gallery Fragment is Active? , if it is then Perform Exit code else Change the Fragment.

//define as field variable
private boolean doubleBackToExit = false;

MyGalleryFragment myFragment = (MyGalleryFragment)getFragmentManager().findFragmentByTag("MY_FRAGMENT");
if (myFragment != null && myFragment.isVisible()) {

    if (doubleBackToExit) {
        super.onBackPressed();
        finishAffinity();
        return;
    }
    this.doubleBackToExit = true;
    toastMsg(getResources().getString(R.string.touch_again_to_exit));

    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            doubleBackToExit = false;
        }
    }, 2000);
} else {
    //Change Layout/Fragment
}

Just Dont forget to Add Tag in Fragment...

fragTrans.replace(android.R.id.content, myFragment, "MY_FRAGMENT");

Hope this will work..!

Have you added Tag with Fragment ? and Added in Activity this code ? — Uttam Panchasara, Sep 26 '16 at 14:22
Yes I did. But I was getting error in the line: "MyGalleryFragment myFragment = (MyGalleryFragment)getFragmentManager().findFragmentByTag("MY_FRAGMENT");" So I did something like this: " Fragment myFragment = getFragmentManager().findFragmentByTag("a");" — Tom Alex, Sep 26 '16 at 14:33
@TomAlex Here i put that as example you need to use your own fragment name instead of `MyGalleryFragment` and dntt forget to **add Tag.** — Uttam Panchasara, Sep 26 '16 at 14:44

score 0 · Answer 3 · answered Sep 26 '16 at 14:01

0

Try using

super.onBackPressed();

instead of

getFragmentManager().popBackStack();

and let us know about the result.

answered Sep 26 '16 at 14:01

A. Badakhshan

1,045
7
22

The same result. The problem is that control always get into the else section. Even after adding a fragment to the back stack. ie, even after (getFragmentManager().getBackStackEntryCount()>0) is false. Any idea whats going on? – Tom Alex Sep 26 '16 at 14:19
What type of activity do you use? Is it AppCompatActivity or FragmentActivity? – A. Badakhshan Sep 27 '16 at 05:47

Press back button twice to exit the app with some condition

3 Answers3