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Codelaby
Asked: 2020-01-12 03:13:41 +0800 CST 2020-01-12 03:13:41 +0800 CST

How to Prevent "blank" fragment loading with popBackStack in Android?

  • 772

I have a side navigation system, by loading fragments using the property addToBackStackso that when the back button is pressed, the last fragment on the fragment control stack is retrieved with the getSupportFragmentManager().popBackStack().

The problem is that when there are no fragments left in the stack it does not exit the application and the application is displayed as if a blank fragment was loaded, it takes another backstroke to exit the application.

How can I prevent loading the blank fragment and exiting the application if there are no more fragments left on the stack?

The control code onBackPressedin MainActivity.java:

@Override
public void onBackPressed() {
    Log.d(TAG, "onBackPressed()");

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);

        Log.d(TAG, "close Drawer");
    } else {
        if (getSupportFragmentManager().getBackStackEntryCount() > 1 ){
            getSupportFragmentManager().popBackStack();

            Log.d(TAG, "fragment Manager popBackStack()");
        } else {
            super.onBackPressed();
        }
    }
}
java

2 Answers

  1. ~~Fixed, replace super.onBackPressed();with finish()y so the app is forced to close.~~

    Edit

    The load of the first fragment is done with addand the others with replace.

    private void addFragment(Fragment newFragment) {
    Log.i(TAG, "addFragment() called with: newFragment = [" + newFragment + "]");
    FragmentManager fm = getSupportFragmentManager();
    FragmentTransaction ft = fm.beginTransaction();
    ft.add(R.id.frame_container, newFragment);
    ft.commit();
}

private void replaceFragment(Fragment newFragment) {
    Log.i(TAG, "replaceFragment() called with: newFragment = [" + newFragment + "]");
    FragmentManager fm = getSupportFragmentManager();
    FragmentTransaction ft = fm.beginTransaction();
    ft.replace(R.id.frame_container, newFragment);
    ft.addToBackStack(newFragment.getClass().getName());
    ft.commit();
}
    • 4
  2. Best Answer

    Regarding your question:

    How to Prevent "blank" fragment loading with popBackStack in Android?

    finish(), it's exclusive to closing the Activity and it works, but you're only closing the Activity.

    the real solution would be not to add the first fragment to the stack, with this you really solve the problem.

    • 2