片段onback按钮按下android跳过片段

Question

I have 4 Fragments ABC D. how to use back stack and how to set fragments? I want to add just Fragment A to stack and when I press back button from BC or D, I want to to set fragment A. I dont want BC and D in back stack

Answer 1

Normally in your FragmentTransaction you should call addToBackstack(null) to add it into backstack.

The backstack is actually a stack where you pop a Fragment when user presses back.

So if A puts B, B puts C and C puts D; you cannot go from D to A directly.

You can override onBackPressed() and control the behavior yourself without using the Fragment's builtin back stack support.

Answer 2

You can popbackstack to clear any fragments in history and ad to backstack fragment A like so :

//create an instance of the fragment you want o be avilable on back press
FragmentA fragmentA = new FragmentA();

FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

//Create instance of the fragment that is going to be loaded
FragmentD fragmentD = new FragmentD();

//Replace the current fragment with Fragment D 
fragmentTransaction.replace(R.id.frame_container, fragmentD);

//Clear frgament history and include the fragment wanted on back press
fragmentManager.popBackStack();

fragmentTransaction.addToBackStack(fragmentA.getclass().getName());

fragmentTransaction.commit();