Fragment onResume() & onPause() is not called on b

Question

I have multiple fragment inside an activity. On a button click I am starting a new fragment, adding it to backstack. I naturally expected the onPause() method of current Fragment and onResume() of new Fragment to be called. Well it is not happening.

LoginFragment.java

public class LoginFragment extends Fragment{
  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
      final View view  =   inflater.inflate(R.layout.login_fragment, container, false);
      final FragmentManager mFragmentmanager =  getFragmentManager();

      Button btnHome  = (Button)view.findViewById(R.id.home_btn);
      btnHome.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view){
           HomeFragment fragment    = new HomeFragment();
           FragmentTransaction ft2   =  mFragmentmanager.beginTransaction();
           ft2.setCustomAnimations(R.anim.slide_right, R.anim.slide_out_left
                    , R.anim.slide_left, R.anim.slide_out_right);
           ft2.replace(R.id.middle_fragment, fragment);
           ft2.addToBackStack(""); 
           ft2.commit();    
         }
      });
  }

  @Override
  public void onResume() {
     Log.e("DEBUG", "onResume of LoginFragment");
     super.onResume();
  }

  @Override
  public void onPause() {
    Log.e("DEBUG", "OnPause of loginFragment");
    super.onPause();
  }
}

HomeFragment.java

public class HomeFragment extends Fragment{
  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
     final View view  =   inflater.inflate(R.layout.login_fragment, container, false);
  }

  @Override
  public void onResume() {
     Log.e("DEBUG", "onResume of HomeFragment");
     super.onResume();
  }

  @Override
  public void onPause() {
     Log.e("DEBUG", "OnPause of HomeFragment");
     super.onPause();
  }
}

What I expected, was,

1. When button is clicked, LoginFragment gets replaced with HomeFragment, onPause() of LoginFragment, and onResume() of HomeFragment gets called
2. When back is pressed, HomeFragment is poped out and LoginFragment is seen, and onPause() of HomeFragment and onResume() of LoginFragment gets called.

What I am getting is,

1. When button is clicked, HomeFragment is correctly replacing LoginFragment, onResume() of HomeFragment is called, but onPause() of LoginFragment is never called.
2. When back pressed, HomeFragment is correctly popping to reveal LoginFragment, onPause() of HomeFragment gets called, but onResume() of LoginFragment never gets called.

Is this the normal behaviour? Why is onResume() of LoginFragment not getting called when I press the back button.

Answer 1

• Since you have used ft2.replace(), FragmentTransaction.remove() method is called and the Loginfragment will be removed. Refer to this. So onStop() of LoginFragment will be called instead of onPause(). (As the new fragment completely replaces the old one).
• But since you have also used ft2.addtobackstack(), the state of the Loginfragment will be saved as a bundle and when you click back button from HomeFragment, onViewStateRestored() will be called followed by onStart() of LoginFragment. So eventually onResume() won't be called.

Answer 2

If you really want to replace fragment inside other fragment you should use Nested Fragments.

In your code you should replace

final FragmentManager mFragmentmanager =  getFragmentManager();

with

final FragmentManager mFragmentmanager =  getChildFragmentManager();

Answer 3

What i do in child fragment:

@Override
public void onDetach() {
   super.onDetach();
   ParentFragment pf = (ParentFragment) this.getParentFragment();
   pf.onResume();
}

And then override onResume on ParentFragment

Answer 4

onPause() method works in activity class you can use:

public void onDestroyView(){
super.onDestroyView    
}

for same purpose..

Answer 5

A fragment must always be embedded in an activity and the fragment's lifecycle is directly affected by the host activity's lifecycle. For example, when the activity is paused, so are all fragments in it, and when the activity is destroyed, so are all fragments

Answer 6

If you add the fragment in XML, you can't swap them dynamically. What happens is they overly, so they events don't fire as one would expect. The issue is documented in this question. FragmenManager replace makes overlay

Turn middle_fragment into a FrameLayout, and load it like below and your events will fire.

getFragmentManager().beginTransation().
    add(R.id.middle_fragment, new MiddleFragment()).commit();