Call an Activity Method from a Fragment

Call an activity method from a fragment

From fragment to activty:

((YourActivityClassName)getActivity()).yourPublicMethod();

From activity to fragment:

FragmentManager fm = getSupportFragmentManager();

//if you added fragment via layout xml
YourFragmentClass fragment = (YourFragmentClass)fm.findFragmentById(R.id.your_fragment_id);
fragment.yourPublicMethod();

If you added fragment via code and used a tag string when you added your fragment, use findFragmentByTag instead:

YourFragmentClass fragment = (YourFragmentClass)fm.findFragmentByTag("yourTag");

call method from fragment to Activity

Call method of Activity from fragment

 ((YourActivityName)getActivity()).addUserLineInfoFragment();

Call method of fragment from Activity

1. Create Interface

 public interface OnButtonListener
    {
        void onButtonClick();
    }

2. Init in Activity

 protected OnButtonListener onActionButtonListener;

    public void setOnButtonListener(OnButtonListener actionButtonListener)
    {
        this.onActionButtonListener = actionButtonListener;
    }

3. In Activity, click event when this action need to perform

this.onActionButtonListener.onButtonClick();

4. Implement listener(OnButtonListener) in Fragment

 @Override
    public void onButtonClick(){}

5. In fragment onCreateView

((YourActivityName) getActivity()).setOnButtonListener(this);

Calling Activity Method From Inside A Fragment

Use getActivity() in your fragment.

MyActivity activity = (MyActivity) getActivity();
activity.myMethod();

if you are not sure if your fragment is attached to MyActivity then

 Activity activity = getActivity();
 if(activity instanceof MyActivity){
      MyActivity myactivity = (MyActivity) activity;
      myactivity.myMethod();
 }

Calling Activity method inside Fragment that is not attached to Activity

First of all, your code is crashing because the Fragment is not attached to an Activity. So a quick fix would be to add a null-check like this:

Activity activity = getActivity();
if (activity != null && activity instanceof HomeActivity) {
       HomeActivity myactivity = (HomeActivity) activity;
       selectedWorkout = myactivity.getSelectedWorkout();
}

That said, accessing the Activity like this is not a good practice, as it couples the Fragment with a specific Activity. There are several better ways to approach it, like:

Approach one:
Make the Activity implement an interface like SelectedWorkoutProvider, move the getSelectedWorkout() method there and cast to the interface, not to HomeActivity

Approach two:
Pass the selected workout to the Fragment via arguments, like this:

Bundle args = new Bundle();
args.putString("selected.workout", getSelectedWorkout());
LandingFragment fragment = new LandingFragment();
fragment.setArguments(args);

And then in the Fragment use:

getArguments().getString("selected.workout");

to get the value.

Approach three:
Use the SharedPreferences to save the data in the Activity and later get it in the Fragment. Please find the documentation for SharedPreferences here

call activity method from inner viewpager fragments

Yes, it is possible. Follow these steps.

1. Make an interface and declare a method.
2. Let the activity implement that interface
3. Now override the method from interface and write the definition for the function.
4. Make the object of the interface in the fragment.
5. Using the object call that method whenever needed.

Example using code : -

Inteface Code :-

//use any name
public interface onInputChangeListener {

    /*To change something in activty*/
    public void changeSomething(//parameters that will hold the new information);


}

Activity Code:-

public class MyActivity extends AppCompatActivity implements onInputChangeListener {

    onCreate();

    @override
    public void changeSomething(/*Arguments with new information*/){

    //do whatever this function need to change in activity
    // i.e give your defination to the function
    }
}

Fragment Code:-

public class MyFragment extends Fragment {

    onInputChangeListener inputChangeCallback;

/*This method onAttach is optional*/
@Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

        // This makes sure that the container activity has implemented
        // the callback interface. If not, it throws an exception
        try {
            inputChangeCallback = (onInputChangeListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement onFragmentChangeListener");
        }
    }


    @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View v = inflater.inflate(R.layout.fragment_my,container,false);
        inputChangeCallback.changeSomething(//pass the new information);
        return v;
    }

}

This would doo.. Cheers!

If you want a quick Fix :-

In your Fragment:-

public class MyFragment extends Fragment {

MyActivity myActivity;

 onCreateView(){
  ...

  myActivity = (MyActivity)getActivity;

  myActivity.callAnyFunctionYouWant();

  ...
 }
}

Call Activity's methods from fragment

What you want is a callback interface for the communication from a Fragment to an Activity. The docs already provide a good example for this.

Define an Interface which your Activity implements:

public interface Callback {
    void doSomething();
}

public class YourActivity implements Callback {
    ...
    @Override
    public void doSomething() {
         // your implementation here
    }
}

In your Fragment use this interface if one of the Buttons are clicked.

public class ServerFragment extends Fragment { 

    Callback iCallback;
    ...
    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            iCallback = (Callback) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException();
        }
    }

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

        btnServer = (Button) view.findViewById(R.id.buttonServer);   
        btnServer.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                iCallback.doSomething();
            }
        });
    }
}

With this approach you can leave your logic in the Activity and handle the UI events in the Fragment. Through the events in the Fragment you can invoke the methods in your Activity.

calling fragment method in Activity not working kotlin

This is activity class

class MyActivity : AppCompatActivity() {
    
        private lateinit var myFragment: FirstFragment
        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
    
            myFragment = FirstFragment()
            supportFragmentManager
                    .beginTransaction()
                    .add(R.id.fragment_container, myFragment , "MyFragment")
                    .commit()
    
            //this is fragment method, we call it from activity
            myFragment.getToast(this)
        }
    
    }

This is fragment class

class FirstFragment: Fragment() {

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return super.onCreateView(inflater, container, savedInstanceState)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
    }

    fun getToast(context: Context) {
       Toast.makeText(context, "Hello", Toast.LENGTH_SHORT).show()
    }
}

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