Question

I’m using the compatibility package v4 in my project and I’m having an issue with keeping a Fragment around after it’s removed from view. I have my Activity displaying 2 fragments…a menu frame on the left, content pane on the right. The menu frame has 3 different menus (Fragments) that can be displayed.

This is how I’m replacing the menu Fragment:

public void showMenuFragment( Fragment fragment, String tag ) {

        showFragment( R.id.menu_frame, fragment, tag, false);
        setLastMenuPushed( tag );
    }

protected void showFragment( int resId, Fragment fragment, String tag, boolean addToBackStack ) {

        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction transaction = fragmentManager.beginTransaction();

        if ( fragmentManager.findFragmentByTag( tag ) != null && fragment.isAdded() ) {
            transaction.remove( fragment );
        }

        transaction.replace( resId, fragment, tag ).setTransition( FragmentTransaction.TRANSIT_FRAGMENT_OPEN ).setBreadCrumbShortTitle( tag );

        if ( addToBackStack ) {
            transaction.addToBackStack( tag );
        }

        transaction.commit();
    }

The menu Fragments require data to be loaded before it can be displayed, so I show a loading spinner. Once it’s loaded the first time, I want to not have to ever load it a second time unless the Activity is finished.

When I call showMenuFragment(...) I try to pass in a Fragment using FragmentManager.findFragmentByTag(String tag) but it’s always null, so I have to make a new Fragment every time I want to show a different menu.

My question is, how do I keep these Fragments around after they are replaced by other menus? I want to avoid keeping manual references to the Fragments because when the device is rotated, the instance of my Activity class is destroyed and I would lose those references.

EDIT: To put in much simpler terms, I want the FragmentManager to keep track of previous Fragments without having to add them to the back stack. I don’t want to hit the back button and see the previous menu shown.

Answer 1

Just figured it out. Instead of removing Fragments when I add new ones, I just hide them, then show them when I want to display them again. Here’s my modified methods:

public void showMenuFragment( Fragment fragment, String tag, boolean addToBackStack ) {

        showFragment( R.id.menu_frame, fragment, tag, getLastMenuPushed(), addToBackStack );
        setLastMenuPushed( tag );
}

protected void showFragment( int resId, Fragment fragment, String tag, String lastTag, boolean addToBackStack ) {

        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction transaction = fragmentManager.beginTransaction();

        if ( lastTag != null ) {
            Fragment lastFragment = fragmentManager.findFragmentByTag( lastTag );
            if ( lastFragment != null ) {
                transaction.hide( lastFragment );
            }
        }

        if ( fragment.isAdded() ) {
            transaction.show( fragment );
        }
        else {
            transaction.add( resId, fragment, tag ).setBreadCrumbShortTitle( tag );
        }

        if ( addToBackStack ) {
            transaction.addToBackStack( tag );
        }

        transaction.commit();
}