Use onBackPressed for fragments

Question

I have to show an animation when go back to previous fragment, so I must use a onBackPressed method. Since it's avaible just in activities, I tried to use a reference:

@Override
onBackPressed(){
super.onBackPressed();
infoFragment.onBackButtonPressed();
}

And in the InfoFragment I defined onBackButtonPressed method but it didn't work. So I tried like this:

view.setFocusableInTouchMode(true);
        view.requestFocus();
        view.setOnKeyListener(new View.OnKeyListener() {
            @Override
            public boolean onKey(View view, int i, KeyEvent keyEvent) {
                if(i==KeyEvent.KEYCODE_BACK){
                    MainActivity mainActivity=(MainActivity)getActivity();
                    mainActivity.loadMainFragment();
                    return true;
                }
                return false;
            }
        });

So, why it didn't work?

The first approach should work just fine, but I don't think that needs a custom back button listener. See http://stackoverflow.com/questions/10886669/how-to-reverse-fragment-animations-on-backstack — Iman Akbari, Jul 30 '16 at 15:54
`onBackPressed()` belongs to the Activity, not to the Fragment — Phantômaxx, Jul 30 '16 at 15:54

score 0 · Answer 1 · edited May 23 '17 at 12:14

If you would like to delay the back press event until your custom animation finishes, you should rewrite your code according to this snippet.

@Override
public void onBackPressed(){
    infoFragment.onBackButtonPressed(new Runnable(){
        @Override
        public void run(){
            super.onBackPressed();
        }
    });
}

What's that runnable?

Your onBackButtonPressed method should get a runnable object and run it once the custom animation is over. This runnable is used as a callback function.

Using this way, you're delaying call to super.onBackPressed(), so you can first play your animation, then relaying the event to your activity's super class.

When should I call this runnable?

For your custom animation, attach an animation listener and call that runnable in onAnimationEnd method of it.

Use onBackPressed for fragments

1 Answers1