CODEWITHSUNDEEP
androidcastingandroid-fragments
IgorGanapolsky
IgorGanapolsky

Reputation: 26821

FragmentActivity: Cannot cast from Fragment to derived class

I am trying to use a Fragment in a FragmentActivity like so:

TutViewerFragment viewer = (TutViewerFragment)    
getSupportFragmentManager().findFragmentById(R.id.tutview_fragment);

And my TutViewerFragment extends Fragment. However I am getting an error:

Cannot cast from Fragment to TutViewerFragment.

I really don't understand why this is happening. Why can't it be cast?

Upvotes: 36

Views: 32537

Answers (5)

Joel Broström
Joel Broström

Reputation: 4050

If you get this and are importing android.support.v4.app.Fragment check that you use supportFragmentManager and Not fragmentManager.

Kotlin:

//DO
import android.support.v4.app.Fragment

myFragment = supportFragmentManager.findFragmentById(R.id.my_fragment) as MyFragment

//DON'T
import android.app.Fragment

myFragment = fragmentManager.findFragmentById(R.id.my_fragment) as MyFragment

Java:

//DO
import android.support.v4.app.Fragment

myFragment =(MyFragment) getSupportFragmentManager().findFragmentById(R.id.my_fragment)

//DON'T
import android.app.Fragment

myFragment = (MyFragment) getFragmentManager().findFragmentById(R.id.my_fragment)

Upvotes: 2

MFAL
MFAL

Reputation: 1110

Just in case people are looking for kotlin equivalent: 

myFragmentClass = supportFragmentManager.findFragmentById(R.id.my_fragment) as MyFindOfFragment

Upvotes: 5

Doogle
Doogle

Reputation: 1264

As devconsole/igor specified, we need to ensure the Fragment class used in both classes is same. i.e. andorid.app.Fragment in both

public class WorkoutDetailFragment extends Fragment

and in the Activity class where we try to get reference of the fragment.

WorkoutDetailFragment workoutDetailFragment = (WorkoutDetailFragment)getFragmentManager().findFragmentById(R.id.detail_frag);

Ensuring the same Fragment class in both files will resolve class cast exception.

Hope this helps. I know its a bit late. I am new to Android and exploring the nuances of the wonderful language. Thanks to Stackoverflow for helping me with resolving these minor issues.

Upvotes: 3

IgorGanapolsky
IgorGanapolsky

Reputation: 26821

As devconsole pointed out in the comment above: The class that extends Fragment needs to import 

android.support.v4.app.Fragment;

and not

android.app.Fragment;

I guess it has to do with the Android Compatibility Package. Problem is now resolved!

Upvotes: 7

devconsole
devconsole

Reputation: 7915

You are extending the wrong Fragment class. Import android.support.v4.app.Fragment instead of android.app.Fragment.

Upvotes: 80

Related Questions