How to replace fragment C with fragment A when back button is pressed?

Question

My scenario : Activity 1 consists of Fragments A-> B-> C. All the fragments are added using this code :

        FragmentManager fm = getSupportFragmentManager()         


        

Answer 1

Theory

Use the addToBackStack(tag: String): FragmentTransaction method from within the FragmentTransaction in order to mark a point where you want to return to. This method returns the FragmentTransaction instance for chain-ability only.

Then Return with the popBackStackImmediate(tag: String, flag: int): void method from the FragmentManager. The tag is what you specified before. The flag is either the constant POP_BACK_STACK_INCLUSIVE to include the transaction marked or 0.

Example

What follows is an example with the following layout having a FrameLayout with id content_frame where the fragments are loaded into.

The code below marks a fragment by it's fragment class name when replacing the content of the layout element with id content_frame.

public void loadFragment(final Fragment fragment) {
    
    // create a transaction for transition here
    final FragmentTransaction transaction = getSupportFragmentManager()
            .beginTransaction();
            
    // put the fragment in place
    transaction.replace(R.id.content_frame, fragment);

    // this is the part that will cause a fragment to be added to backstack,
    // this way we can return to it at any time using this tag
    transaction.addToBackStack(fragment.getClass().getName());

    transaction.commit();
}

And to complete this example a method that allows you to get back to that exact same fragment using the tag when you loaded it.

public void backToFragment(final Fragment fragment) {

    // go back to something that was added to the backstack
    getSupportFragmentManager().popBackStackImmediate(
            fragment.getClass().getName(), 0);
    // use 0 or the below constant as flag parameter
    // FragmentManager.POP_BACK_STACK_INCLUSIVE);

}

When implementing this for real you might want to add a null check on the fragment parameter ;-).