How to implement onBackPressed in fragment

In this android programming source code example, we are going to implement onBackPressed in fragment.

Below is a step by step source code to implement onBackPressed in fragment.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ededed">

    <FrameLayout
        android:id="@+id/frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</RelativeLayout>

MainActivity.java

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class FragmentActivity4 extends AppCompatActivity {
    protected OnBackPressedListner onBackPress;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fragment4);
        FragmentManager mFragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.frame,new Fragment4()).commit();
    }

    @Override
    public void onBackPressed(){
       Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.frame);
       if(!(fragment instanceof  OnBackPressedListner)|| !((OnBackPressedListner)fragment).onBackPressed()){
           super.onBackPressed();
       }
    }

    public interface OnBackPressedListner{
        boolean onBackPressed();
    }

}

fragment_fragment4.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ededed">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="OnBackPress In Fragment"
        android:gravity="center"
        android:textSize="20sp"/>

</RelativeLayout>

Fragment4.java

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.Toast;

import com.bluapp.androidview.R;

public class Fragment4 extends Fragment implements FragmentActivity4.OnBackPressedListner{

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_fragment4, container, false);

        return view;
    }

    @Override
    public boolean onBackPressed() {
        Toast.makeText(getActivity(),"OnBackpress Click",Toast.LENGTH_LONG).show();
        return false;
    }
}

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