How to change Screen Orientation programmatically using a Button in Android?

This example demonstrates about how do I change the Screen Orientation programmatically using a Button in Android.
Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project
Step 2 − Add the following code to res/layout/activity_main.xml.
<?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=".MainActivity">
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/buttonSetPotrait"
      android:text="Click here change Orientation"
      android:textColor="@color/colorPrimaryDark"
      android:textStyle="bold"
      android:layout_marginTop="62dp"
      android:layout_centerHorizontal="true" />
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/buttonSetLandscape"
      android:text="Click here change Orientation"
      android:textColor="@color/colorPrimaryDark"
      android:textStyle="bold"
      android:layout_marginTop="62dp"
      android:layout_centerHorizontal="true"/>
</RelativeLayout>
Step 3 − Add the following code to src/MainActivity.java
package app.com.sample;
import android.content.pm.ActivityInfo;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      Button buttonSetPortrait = (Button)findViewById(R.id.buttonSetPotrait);
      Button buttonSetLandscape = (Button)findViewById(R.id.buttonSetLandscape);
      buttonSetPortrait.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
         }
      });
      buttonSetLandscape.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
         }
      });
   }
}
Step 4 − Add the following code to androidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.sample">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>
Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen −
Click here to download the project code.