Fragment-Fragment communication in Android

Question

I am at beginner level in Android programming, so I need your sincere help for this. Anyone help me please.

I am trying to build a SLIDING UI using fragments

so my actual doubt is ... I have a Fragment (say Fragment A) it has a TextView and Button in it and another Fragment (say Fragment B). It has a TextView in it. I need to show the Fragment A's TextView's content in Fragment B's TextView, when I pressed the Button in FRAGMENT A. I tried many ways, unfortunately I didn't got the proper output. I am sure you peoples know about it. Please help me.

Thank you

Answer 1

It should be done thought listener, so Fragments are still not depend on each other and can be used in one or two pane mode. Activity should handle listeners of both fragments.

Here is an example of activity with two Fragments:

package com.example;

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;

import com.example.fragment.FragmentA;
import com.example.fragment.FragmentA.TextChangeListener;
import com.example.fragment.FragmentB;

public class ActivityAB extends FragmentActivity {

    FragmentA fragmentA;
    FragmentB fragmentB;

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

        FragmentManager manager = getSupportFragmentManager();
        fragmentA = (FragmentA) manager.findFragmentById(R.id.fragmentA);
        fragmentB = (FragmentB) manager.findFragmentById(R.id.fragmentB);

        fragmentA.setTextChangeListener(new TextChangeListener() {

            @Override
            public void onTextChange(CharSequence newText) {
                fragmentB.updateTextValue(newText);
            }
        });
    }

}

Here is Fragment A, that has custom listener for text change event.

package com.example.fragment;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

import com.example.R;

public class FragmentA extends Fragment {

    TextChangeListener listener;

    public interface TextChangeListener {
        public void onTextChange(CharSequence newText);
    }

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

        Button btn = (Button) view.findViewById(R.id.button1);
        final TextView textView = (TextView) view.findViewById(R.id.textView1);

        btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                if (null != listener) {
                    listener.onTextChange(textView.getText());
                }

            }
        });
        return view;
    }

    public void setTextChangeListener(TextChangeListener listener) {
        this.listener = listener;
    }
}

Here is Fragment B that has public method to update text field:

package com.example.fragment;

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

import com.example.R;

public class FragmentB extends Fragment {

    TextView textView;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_b, container, false);
        textView = (TextView) view.findViewById(R.id.textView1);
        return view;
    }

    public void updateTextValue(CharSequence newText) {
        textView.setText(newText);
    }
}

ActivityAB xml Layout:

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

    <fragment
        android:id="@+id/fragmentA"
        android:name="com.example.fragment.FragmentA"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1" />

    <fragment
        android:id="@+id/fragmentB"
        android:name="com.example.fragment.FragmentB"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1" />

</LinearLayout>

Fragment A xml layout:

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

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="This is text"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Show" />

</LinearLayout>

Fragment B xml layout:

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

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="(here will be text)"
        android:textAppearance="?android:attr/textAppearanceLarge" />

</LinearLayout>

Answer 2

It sounds as if your setup might be something like - MainActivity w/ FragmentA [added] and FragmentB [added]. For this case, I would delegate messages/actions between the two fragments through the MainActivity. Allowing MainActivity to handle the messages/actions also facilitates 'special' orchestrations which might be needed in a more complex situation between the Fragments. For example:

public interface FragmentCommunicator
{
    public void sendMessage ( String broadcastMessage );
    public void takeAction ( String name, int action, Fragment frag );
}

public class MainActivity extends Activity implements FragmentCommunicator
{
    Fragment fragA;
    Fragment fragB;
    ...
    @Override
    public void sendMessage ( String msg )
    {
        if ( msg.Contains("Send To fragA") )
            fragA.receiveMsg(msg);
        ...
    }
    @Override
    public void takeAction ( String name, int action, Fragment frag )
    {
    if ( action == CLOSE )
            removeFragment( name, frag );
        ...
    }
}

public class FragmentA extends Fragment
{
    ...
@Override
public void onClick(View v)
{   
     FragmentCommunicator inter = (FragmentCommunicator) getActivity();
     inter.sendMessage("the txt/information/etc you want to send to fragB");    
}
}

public class FragmentB extends Fragment
{
    ...
    public void receiveMsg ( String msg )
    {
        textView.setText(msg);
    }
}

I forgot to post the send portion of FragmentA. Hope this helps.