Android UI How to - Interactions between Fragments

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We can make fragments to communicate with one another and exchange data.

Example

The following code shows how one fragment can access the views contained within another fragment.

In the res/layout folder, add a new file and name it fragment1.xml. Populate it with the following:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout/*  w  w  w. ja  va  2 s .co m*/
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#00FF00" >
<TextView
    android:id="@+id/lblFragment1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="This is fragment #1"
    android:textColor="#000000"
    android:textSize="25sp" />
</LinearLayout>

Also in the res/layout folder, add another new file and name it fragment2.xml. Populate it as follows:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout// w  w  w  .j  a v a  2s. c  o m
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#FFFE00" >
<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="This is fragment #2"
    android:textColor="#000000"
    android:textSize="25sp" />

<Button
    android:id="@+id/btnGetText"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Get text in Fragment #1"
    android:textColor="#000000"
    android:onClick="onClick" />

</LinearLayout>

In activity_main.xml, add the following code:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"
      android:orientation="horizontal" >
//ww w.j a  va  2 s  .co m
      <fragment
          android:name="com.java2s.myapplication3.app.Fragment1"
          android:id="@+id/fragment1"
          android:layout_weight="1"
          android:layout_width="0px"
          android:layout_height="match_parent" />
      <fragment
          android:name="com.java2s.myapplication3.app.Fragment2"
          android:id="@+id/fragment2"
          android:layout_weight="1"
          android:layout_width="0px"
          android:layout_height="match_parent" />

</LinearLayout>

Modify the MainActivity.java file as follows:

public class MainActivity extends Activity {
   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);
   }
}

Under the com.java2s.Fragments package name, add two Java class files and name them Fragment1.java and Fragment2.java

Add the following code to Fragment1.java:

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
//w  ww  .  ja  v  a  2  s .c  om
public class Fragment1 extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater,
    ViewGroup container, Bundle savedInstanceState) {
        //Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment1, container, false);
    }
}

Add the following code to Fragment2.java:

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
/*w ww .  j a  va2  s  .com*/
public class Fragment2 extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater,
    ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(
            R.layout.fragment2, container, false);
    }

    @Override
    public void onStart() {
        super.onStart();
        Button btnGetText = (Button)
            getActivity().findViewById(R.id.btnGetText);
        btnGetText.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                TextView lbl = (TextView)
                    getActivity().findViewById(R.id.lblFragment1);
                Toast.makeText (getActivity(), lbl.getText(),
                    Toast.LENGTH_SHORT).show();
            }
        });
    }

}

Note

Debug the application on the Android emulator.

In the second fragment on the right, click the button. You should see the Toast class displaying the text "This is fragment #1".

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