In this tutorial we are going to implement an up/back button into our app, which navigates us back to our parent Activity.

For this we have to make some small changes in our Manifest.xml file.

In manifest.xml file add these lines of code:-

<activity android:name=".Activity2"
android:parentActivityName=".MainActivity"></activity>

<activity android:name=".Activity3"
android:parentActivityName=".Activity2"></activity>

In MainActivity.java class file add these lines of codes:-

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 {
private Button button;

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

button = (Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
openActivity2();
}
});
}

public void openActivity2() {
Intent intent = new Intent(this, Activity2.class);
startActivity(intent);
}

}

In activity.xml file add these lines of code:-

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.application.upbuttonexample.MainActivity">

<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="open activity 2" />

</RelativeLayout>

In Activity2.java class file add these lines of code:-

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

public class Activity2 extends AppCompatActivity {
private Button button2;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_2);

getSupportActionBar().setTitle("Activity 2");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);

button2 = (Button) findViewById(R.id.button2);
button2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
openActivity3();
}
});
}

public void openActivity3() {
Intent intent = new Intent(this, Activity3.class);
startActivity(intent);
}

}

In activity2.xml file add these lines of codes:-

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.application.upbuttonexample.Activity2">

<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="open activity 3" />

</RelativeLayout>

In Activity3.java class file add these lines of codes:-

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

public class Activity3 extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_3);

getSupportActionBar().setTitle("Activity 3");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}

}

In activity_3.xml file add these lines of codes:-

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.application.upbuttonexample.Activity3">

</RelativeLayout>

Now Run the code and you will see the desired output. Thank you. :)

Up Button

Deep Structural Diagnostics.

Neural Engine