The back button is the very important concept.Nowadays, Back button use's every android apps.If we want to use the back button in our app.So this is the process.

  • First, you have to open new empty project.
  • Here we will need two activities.
  •  So we will create a new activity. for creating new activity go resource folder use right click choose New after that choose Activity after that we have to choose an Empty activity.
  • Choose first XML page and create here Button code for jumping the second page.
<Button
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:textSize="35dp"
       android:text="Click"
       android:id="@+id/button"/>
  • Choose MainActivity.java page and here use the Intent code for jumping the second page. 
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button=findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent(MainActivity.this,Main2Activity.class);
                startActivity(intent);
            }
        });
    }
}
  • Choose second activity MainActivity.java page.
  • Create this code in the Oncreate method
if (getSupportActionBar()!=null)
{
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}
  • After creating this code use this code out of an Oncreate method
@Override
public boolean onOptionsItemSelected(MenuItem item)
{
    if (item.getItemId()==R.id.home);
    finish();
    return super.onOptionsItemSelected(item);
}
  • Run the program and check. 

Back Button All Codes :-)

  • activity_main.XML Page Code.
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="35dp"
        android:text="Click"
        android:id="@+id/button"/>
</android.support.constraint.ConstraintLayout>
  • MainActivity.java All Codes:-) 
package waytofeed.wapptech.com.backbuttoncode;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button=findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent=new Intent(MainActivity.this,Main2Activity.class);
                startActivity(intent);
            }
        });
    }
}
  • activity_main .xml All Codes:-)
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".Main2Activity">

</android.support.constraint.ConstraintLayout>
  • MainActivity2.java All Codes:-)
package waytofeed.wapptech.com.backbuttoncode;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;

public class Main2Activity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        if (getSupportActionBar()!=null)
        {
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        }
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        if (item.getItemId()==R.id.home);
        finish();
        return super.onOptionsItemSelected(item);
    }
}

Github Link:-) https://github.com/Sudarshan101/androidBackButtonAction 

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