Back press fragments issue in android

问题:

I have four Fragments: A, B, C, D. Now I am moving from A --> B so my code will be

from A to B

getActivity().getSupportFragmentManager()
    .beginTransaction()
    .replace(R.id.content_frame, new B())
    .addToBackStack("A")
    .commit();

Now from B to C so code will be

getActivity().getSupportFragmentManager()
    .beginTransaction()
    .replace(R.id.content_frame, new C())
    .addToBackStack("B")
    .commit();

Now from C to D. But I don't want to include C in backstack because on back press I don't want C fragment to be shown.

 getActivity().getSupportFragmentManager()
     .beginTransaction()
     .replace(R.id.content_frame, new D())
     .commit();

Now when I press Back button it will work perfectly upto A. Now if I repeat same process again. Now again on back press From D Fragment, I will be sent directly on A fragment instead of B fragment. Can you please figure it out the mistake that I am doing in above code?

回答1:

You have to provide same String value for addToBackStack for single Stack.

.replace(R.id.content_frame, new B())
.addToBackStack("stack") 

.replace(R.id.content_frame, new C())
.addToBackStack("stack") 

回答2:

Here is the code of BackStackChangedListener.

public  static void performNoBackStackTransaction( final FragmentManager fragmentManager, String tag, Fragment fragment) {
    final int newBackStackLength = fragmentManager.getBackStackEntryCount() +1;

    fragmentManager.beginTransaction()
            .replace(R.id.content_frame, fragment, tag)
            .addToBackStack(tag)
            .commit();

    fragmentManager.addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
        @Override
        public void onBackStackChanged() {
            int nowCount = fragmentManager.getBackStackEntryCount();
            if (newBackStackLength != nowCount) {
                // we don't really care if going back or forward. we already performed the logic here.
                fragmentManager.removeOnBackStackChangedListener(this);

                if ( newBackStackLength > nowCount ) { // user pressed back
                    fragmentManager.popBackStackImmediate();
                }
            }
        }
    });
}