Fragment isAdded() returns false on an already added Fragment

问题

I have this neat function:

private void addMapFragment(){
    if(!mapFragment.isAdded()){
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        ft.add(R.id.mapContainer, mapFragment);
        ft.commit();
    }
}

I'm calling addMapFragment() in my activity's onCreate(). I then have a callback from a webrequest that calls addMapMapFragment(). The isAdded() method doesn't look useful at all since I'm getting a crash saying "Fragment already added: MapFragment[...]"

Any clue?

回答1:

FragmentTransactions are committed asynchronously. Therefore, you need to call

getFragmentManager().executePendingTransactions();

before you call

Fragment.isAdded();

That way, you can make sure that everything is up to date.

回答2:

Instead, check getSupportFragmentManager.findFragmentById() and see if you are getting the expected fragment back. If now you can add and commit.

来源：https://stackoverflow.com/questions/22485899/fragment-isadded-returns-false-on-an-already-added-fragment