问题
How do I properly use Fragments in Fragments?
My (simplified) use case is following, I have an activity with a layout fragment and this fragment theirself contains a sub fragment... all fragments are added manually to their parents...
----------------------------------------------------------
- Activity -
- -
- -
- --------------------------------------- -
- - Fragment - -
- - - -
- - ----------------- - -
- - - SubFragment - - -
- - - - - -
- - - - - -
- - ----------------- - -
- --------------------------------------- -
- -
----------------------------------------------------------
Now in my activity's onCreate
I do following:
if (savedInstanceState == null)
{
// I create the fragment
mMainFragment = new MainFragment();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment_main, mMainFragment);
transaction.commit();
}
else
{
// I retrieve the fragment
mMainFragment = (BaseFragment) getSupportFragmentManager().findFragmentById(R.id.fragment_main);
}
And in my fragments onCreate
I get/create my SubFragment:
mSubFragment = getChildFragmentManager().findFragmentByTag(SubFragment.class.getName());
if (mSubFragment == null)
{
mSubFragment = new SubFragment();
getChildFragmentManager().beginTransaction().add(R.id.fragment_sub, mSubFragment, SubFragment.class.getName()).commit();
}
Problem
After screen rotation, my SubFragment is added twice... If I use the activity's FragmentManager
then it works... But why does it not work with the ChildFragmentManager
? Of course, the Fragment is a new fragment, but the activity is a new one as well, so why does it work with the activity's FragmentManager
but not with the parent fragment's one?
In a fragment, I should use the fragments ChildFragmentManager
, shouldn't I?
回答1:
You should add SubFragment
to Fragment
the same way like you add Fragment
to Activity
. I mean adding Fragment
to Activity
should look like:
@Override
public void onCreate(Bundle savedInstanceState) {
....
if (savedInstanceState == null){
//add fragment
mMainFragment = new MainFragment();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment_main, mMainFragment);
transaction.commit();
}
}
Adding SubFragment
to MainFragment
should look like:
public class MainFragment extends Fragment{
@Override
public View onCreateView(LayoutInflater i, ViewGroup c, Bundle savedInstanceState) {
...
if (savedInstanceState == null){
mSubFragment = new SubFragment();
//add child fragment
getChildFragmentManager()
.beginTransaction()
.add(R.id.fragment_sub, mSubFragment, "tag")
.commit();
}
}
}
or you can add child fragment to Fragment
in onCreate
method
来源:https://stackoverflow.com/questions/20676690/proper-use-of-sub-sub-fragments-with-childfragmentmanager