Demonstrates how to call a function in the parent Activity from within a Fragment.

ActivityEventListener.md

Step 1: Add any functions you want to call into the interface (EventListener).

Step 2: Implement those functions in your MainActivity.

Step 3: Create the listener in your Fragment and attach it to the Activity.

Step 4: Call any functions on the listener.

DetailFragment.java

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * Created by cblack on 8/15/13.
 */
public class DetailFragment extends Fragment {
    private EventListener listener;

    @Override
    public void onAttach(Activity activity)
    {
        super.onAttach(activity);
        if(activity instanceof EventListener) {
            listener = (EventListener)activity;
        } else {
            // Throw an error!
        }
    }

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

        View v = inflater.inflate(R.layout.fragment_detail, container, false);
        
        listener.sendDataToActivity("Hello World!");

        return v;
    }
}

EventListener.java

/**
 * Created by cblack on 8/15/13.
 */
public interface EventListener {

    public void sendDataToActivity(String data);
    
}

fragment_detail.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

</LinearLayout>

MainActivity.java

import android.os.Bundle;
import android.app.Activity;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.Menu;

public class MainActivity extends FragmentActivity implements EventListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.x_activity_main);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public void sendDataToActivity(String data) {
        Log.i("MainActivity", "sendDataToActivity: " + data);
    }
}

x_activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <fragment
            android:name="com.example.listenerdemo.DetailFragment"
            android:id="@+id/detail_fragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

</RelativeLayout>

I want to shake your hand! Hours spent searching how to do this. I'm new to the language and people don't often realize how much context they're leaving out when they offer solutions, so I tried this style of implementation before but it never worked. It wasn't until I saw your clear, complete code that it clicked and it works for me. Thank you!