Communication Between Fragments In Android

Introduction

Here I will explain the communication between fragments in Android. The following is a brief description of the task that I am going to show you.

I have an Activity with two fragments, lets name that fragments to FragmentA and Fragment B. FragmentA contains a Button and FragmentB contains a textview

Each time the user clicks on the Button of FragmentA then the textview in the FragmentB will update its text like "this button is clicked <counter> times".

This is the task I am going to show you.

For this first, create FragmentA and its Layout,

<?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:background="@android:color/darker_gray" android:layout_height="match_parent">
<Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Click Me" android:layout_margin="20dp" android:id="@+id/button" android:layout_gravity="center_horizontal" />
</LinearLayout>

The FragmentA contains a Button and in the java code please load the XML file in onCreateView();

Now create FragmentB and its Layout,

<?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:background="@android:color/white" android:layout_height="match_parent">
<TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_margin="20dp" android:textAppearance="?android:attr/textAppearanceLarge" android:text="Large Text" android:id="@+id/textView" android:layout_gravity="center_horizontal" />
</LinearLayout>

FragmentB contains a Textview only. load this layout to FragmetB class on the onCreateView()

Now create the main part of the task that is communicator Interface.

public interface Communicator
{
public void clicked(String text);
}

Now create the MainActivity that implement Communicator Interface,

public class MainActivity extends Activity implements Communicator
{
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
public void clicked(String text)
{
FragmentB b = (FragmentB) getFragmentManager().findFragmentById(R.id.fragment2);
b.chageText(text);
}
}

The clicked method will call another method named changeText(String) in Fragment B. Now we need to notify the communicator Interface when Button in FragmentA is clicked and create a method chageText(String) in FragmentB.

Now create Button Click Event in FragmentA. This is how the FragmentA will look like,

public class FragmentA extends Fragment
{
private int counter = 0;
private Communicator comm = null;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
return inflater.inflate(R.layout.fragment_a, container, false);
}
@Override
public void onActivityCreated(Bundle savedInstanceState)
{
super.onActivityCreated(savedInstanceState);
Button button = (Button) getActivity().findViewById(R.id.button);
comm = (Communicator) getActivity();
button.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View view)
{
counter++;
comm.clicked("This button is clicked " + counter + " times");
}
});
}
}

On the onActivityCreated() we are initializing the communicator with the FragmentA, and in the button click we are firing the interface method()

Now Create the FragmentB,

public class FragmentB extends Fragment
{
private TextView textView = null;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
return inflater.inflate(R.layout.fragment_b, container, false);
}
@Override
public void onActivityCreated(Bundle savedInstanceState)
{
super.onActivityCreated(savedInstanceState);
textView = (TextView) getActivity().findViewById(R.id.textView);
}
public void chageText(String data)
{
textView.setText(data);
}
}

There will be a method named chageText to change the content of textView in FragmentB. This is the way in which the fragments communicate in Android.

The output will look as follows,