Using onBackPressed() in Android Fragments

Question

I am working on a project and I need to be able to use the back button in each fragment to navigate between previous fragments, I have methods written to do so by using a back arrow in the action bar, however, I want to be able to use the same functionality on the back button pressed. I don't want to use the back stack. Is there a way to do this?

EDIT

Rather than using the back stack I want to be able to call the go back to previous method below when the user clicks the back button. I need to used the gobackpressed method within fragments. Is this possible? I hope this is clear and concise. Apologies for any confusion caused above.

Go Back to Previous

public void gobackToPreviousFragment(String preFragmentTag, Fragment preFragment){

    FragmentManager  fm = getSupportFragmentManager();

    FragmentTransaction ft = fm.beginTransaction();
    ft.setCustomAnimations(R.animator.close_slide_in,R.animator.close_slide_out);

    ft.show(preFragment);

    //**BY REMOVING FRAGMENT, WHEN USER TRIES TO REVISIT, FRAGMENT IS BLACK**

    ft.remove(fm.findFragmentByTag(Misc.currentContentFragmentTag));
    ft.addToBackStack(null);
    ft.commit();

    Misc.currentContentFragmentTag = preFragmentTag;

    createBar(preFragment);
}

Go Forward

public void gotoNextFragment(String nextTag, Fragment nextFragment){

    FragmentManager  fm = getSupportFragmentManager();

    FragmentTransaction ft = fm.beginTransaction();
    ft.setCustomAnimations(R.animator.enter_slide_in, R.animator.enter_slide_out);

    boolean newlyCreated = false;
    if(nextFragment == null){
        nextFragment = Fragment.instantiate(this, nextTag);
        newlyCreated = true;
    }

    //hide current fragment
    ft.hide(fm.findFragmentByTag(Misc.currentContentFragmentTag));

    if(newlyCreated){
        ft.add(R.id.content_frame, nextFragment, nextTag);
    }
    else{
        ft.show(nextFragment);
    }

    ft.addToBackStack(null);
    ft.commit();
    Misc.currentContentFragmentTag = nextTag;

    createBar(nextFragment);
}

These are how I navigate back and forth, and I'd like to be able to implement the go back method on the onBackPressed(). Does this make sense?

Answer 1

I didn't find any good answer about this problem, so this is my solution.

If you want to get backPress in each fragment do the following.

create interface OnBackPressedListener

public interface OnBackPressedListener {
    void onBackPressed();
}

That each fragment that wants to be informed of backPress implements this interface.

In parent activity , you can override onBackPressed()

@Override
public void onBackPressed() {
    List<Fragment> fragmentList = getSupportFragmentManager().getFragments();
    if (fragmentList != null) {
        //TODO: Perform your logic to pass back press here
        for(Fragment fragment : fragmentList){
           if(fragment instanceof OnBackPressedListener){
               ((OnBackPressedListener)fragment).onBackPressed();
           }
        }
    }
}

Answer 2

Why don't you want to use the back stack? If there is an underlying problem or confusion maybe we can clear it up for you.

If you want to stick with your requirement just override your Activity's onBackPressed() method and call whatever method you're calling when the back arrow in your ActionBar gets clicked.

EDIT: How to solve the "black screen" fragment back stack problem:

You can get around that issue by adding a backstack listener to the fragment manager. That listener checks if the fragment back stack is empty and finishes the Activity accordingly:

You can set that listener in your Activity's onCreate method:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    FragmentManager fm = getFragmentManager();
    fm.addOnBackStackChangedListener(new OnBackStackChangedListener() {
        @Override
        public void onBackStackChanged() {
            if(getFragmentManager().getBackStackEntryCount() == 0) finish();
        }
    });
}

Answer 3

requireActivity().onBackPressedDispatcher.addCallback(viewLifecycleOwner, object : OnBackPressedCallback(true) {
            override fun handleOnBackPressed() {
                Log.w("a","")
            }
        })

Answer 4

In the fragment where you would like to handle your back button you should attach stuff to your view in the oncreateview

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.second_fragment, container, false);
    v.setOnKeyListener(pressed);
    return v;
}



@Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
    // TODO Auto-generated method stub
    if( keyCode == KeyEvent.KEYCODE_BACK ){
            // back to previous fragment by tag
            myfragmentclass fragment = (myfragmentclass) getActivity().getSupportFragmentManager().findFragmentByTag(TAG);
            if(fragment != null){
                (getActivity().getSupportFragmentManager().beginTransaction()).replace(R.id.cf_g1_mainframe_fm, fragment).commit();
            }
            return true;
        }
        return false;
    }
};

Answer 5

This works for me :D

    @Override
    public void onResume() {
    super.onResume();

    if(getView() == null){
        return;
    }

    getView().setFocusableInTouchMode(true);
    getView().requestFocus();
    getView().setOnKeyListener(new View.OnKeyListener() {
        @Override
        public boolean onKey(View v, int keyCode, KeyEvent event) {

            if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK){
                // handle back button's click listener
                return true;
            }
            return false;
        }
    });}

Answer 6

You can try to override onCreateAnimation, parameter and catch enter==false. This will fire before every back press.

@Override
public Animation onCreateAnimation(int transit, boolean enter, int nextAnim) {            
        if(!enter){
            //leaving fragment
            Log.d(TAG,"leaving fragment");
        }
        return super.onCreateAnimation(transit, enter, nextAnim);
    }

Answer 7

For a Fragment you can simply add

  getActivity().onBackPressed();

to your code

Answer 8

I found a new way to do it without interfaces. You only need to add the below code to the Fragment’s onCreate() method:

//overriding the fragment's oncreate 
override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        //calling onBackPressedDispatcher and adding call back

        requireActivity().onBackPressedDispatcher.addCallback(this) {

      //do stuff here
            
        }
    }

Answer 9

Use this:

@Override
public void onBackPressed() {
    int fragments = getFragmentManager().getBackStackEntryCount();
    if (fragments == 1) {
        finish();
    }
    super.onBackPressed();
}