Fragment Back Button Navigation

Question

Suppose I have 3 Fragments: A,B,C

1. I go from A -> B
2. B -> C
3. C -> B (without pressing back button)
4. B -> C (without pressing back button)
5. C -> B (without pressing back button)
6. B -> C (without pressing back button)

Now by pressing Back Button, Navigation should be C->B->A -> finish

In other words, irrespective of number of navigation (without pressing back button) between B->C and C->B, back navigation by pressing back button should in order C->B->A

Answer 1

Assuming that all the allowed transitions are A<->B<->C, you can use FragmentManager.popBackStack() method when navigating C->B, and always add the transition to back stack when navigating B->C.

Here's how to do the transitions:

public void transitionFromAToB() {
    getSupportFragmentManager().beginTransaction()
            .replace(R.id.fragment_container, new FragmentB())
            .addToBackStack(null)
            .commit();
}

public void transitionFromBToC() {
    getSupportFragmentManager().beginTransaction()
            .replace(R.id.fragment_container, new FragmentC())
            .addToBackStack(null)
            .commit();

}

public void tansitionFromCToB() {
    getSupportFragmentManager().popBackStack();
}

public void transitionFromBToA() {
    getSupportFragmentManager().popBackStack();
}

So when transitioning C->B, you're not actually doing a new transition, you're actually just reversing the B->C transition.