Passing data From Activity to Fragment using interface [closed]

Answer 1

Activities contain fragments, you shouldn't need to pass anything. One technique would be to store your data in the activity scope and get a reference to it with getActivity().

Best practice to reference the parent activity of a fragment?

As far as the code you posted, I don't see where you call your pass data method within the fragment. I would suggest calling it in onviewcreated().

I will attempt to provide some sample code later as doing this on my mobile device is proving difficult.

Try passdata (getActivity ().someStringVariable);

Answer 2

In your Fragment class, have a TAG field. Naming a fragment Fragment can be a bit confusing as it is the same name as an Android Fragment, so I will use ExampleFragment:

public class ExampleFragment extends android.support.v4.app.Fragment implements FragmentCommunicator {
    public static final String TAG = "ExampleFragment";

    // ...
}

Now, when you replace the fragment in the activity, make sure to pass the TAG:

getSupportFragmentManager().beginTransaction().replace(R.id.container ,fragment, ExampleFragment.TAG).commit();

Note that in your case it would be Fragment.TAG, but I used ExampleFragment to clarify that Fragment.TAG is not part of the Android SDK.

To get a reference of your fragment in your activity, use the FragmentManager to find your fragment:

Fragment myFragment = getSupportFragmentManager().findFragmentByTag(ExampleFragment.TAG);

You can then make sure that myFragment is not null and cast it to FragmentCommunicator:

if (myFragment != null) {
    fragmentCommunicator = (FragmentCommunicator) myFragment;
}

Note that in your example fragmentCommunicator = (FragmentCommunicator) getApplication(); is invalid because it is your fragment that is implementing the interface, not your application.

Answer 3

Write this line of code after onCreate method.

public void passVal(FragmentCommunicator fragmentCommunicator) {
    this.fragmentCommunicator = fragmentCommunicator;
}

Something like this

public class MainActivity extends AppCompatActivity{

FragmentCommunicator fragmentCommunicator;
private Fragment fragment;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Button b = (Button) findViewById(R.id.button);

    fragment= new Fragment();

    //App is crasing for this line. Working fine by removing it
    //fragmentCommunicator = (FragmentCommunicator) getApplication();

    //fragmentCommunicator.passData("hello");
    getSupportFragmentManager().beginTransaction().replace(R.id.container ,fragment).commit();

    b.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            fragmentCommunicator.passData("Hello");

        }
    });

  }

   //Here is new method
   public void passVal(FragmentCommunicator fragmentCommunicator) {
       this.fragmentCommunicator = fragmentCommunicator;

   }
}

Then write this line of code into onCreateView() of your fragment. Something like this

@Override 
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup  container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment, null);

((MainActivity) getActivity()).passVal(new FragmentCommunicator() {
       @Override
       public void passData(String name) {
           Toast.makeText(c, name, Toast.LENGTH_SHORT).show();
       }
   });
  return view;
}

Note: no need to implement FragmentCommunicator interface in your fragment. Hope it works. It works for me. I have tested