片段之间的Android导航

Question

I have a form divided in few fragments. I call every fragment with:

final FragmentManager fm = getSupportFragmentManager();
final FragmentTransaction ft = fm.beginTransaction();
if(fragment.equals(this.formOne) ||   fragment.equals(this.formTwo)) {
        ft.setCustomAnimations(android.R.anim.slide_in_left,android.R.anim.slide_out_right);
    }

ft.replace(R.id.fragForm, fragment);
ft.addToBackStack(null);
ft.commit();

When I click on the back button it skips the previous Fragment and goes back to the Activity but with a blank screen.

For example, I have 3 fragments : A - B - C

If I go to C and want to go back to the previous Activity, I click on the back button so I'm on B, I click again and I'm on A, and when I click again, I have a blank screen, I need to click another time to come back to the previous activity.

I don't understand why have I this blank screen on my Activity.

I don't understand this in the developer documentation:

Note: You should not add transactions to the back stack when the transaction is for horizontal navigation (such as when switching tabs) or when modifying the content appearance (such as when adjusting filters). For more information, about when Back navigation is appropriate, see the Navigation design guide.

If we can't use that, what is the solution?

Answer 1

Don't add it to the backstack when you add fragment A.

ft.add(R.id.fragForm, fragmentA);
ft.commit();


ft.replace(R.id.fragForm, fragmentB);
ft.addToBackStack(null);
ft.commit();

ft.replace(R.id.fragForm, fragmentC);
ft.addToBackStack(null);
ft.commit();

Answer 2

If you don't have to Navigate to previous fragment don't add it to the backstack

Remove this

 ft.addToBackStack(null);