Start an Activity from a Notification in Android?

This example demonstrate about Start an Activity from a Notification 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" ?>
<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"
   android :padding = "16dp"
   tools :context = ".MainActivity" >
   <Button
      android :id = "@+id/btnCreateNotification"
      android :layout_width = "0dp"
      android :layout_height = "wrap_content"
      android :text = "Create notification"
      app :layout_constraintBottom_toBottomOf = "parent"
      app :layout_constraintEnd_toEndOf = "parent"
      app :layout_constraintStart_toStartOf = "parent"
      app :layout_constraintTop_toTopOf = "parent" />
</android.support.constraint.ConstraintLayout>
Step 3 − Add the following code to src/MainActivity.java
package app.tutorialspoint.com.notifyme ;
import android.app.NotificationChannel ;
import android.app.NotificationManager ;
import android.app.PendingIntent ;
import android.content.Context ;
import android.content.Intent ;
import android.support.v4.app.NotificationCompat ;
import android.support.v7.app.AppCompatActivity ;
import android.os.Bundle ;
import android.view.View ;
import android.widget.Button ;
public class MainActivity extends AppCompatActivity {
   public static final String NOTIFICATION_CHANNEL_ID = "10001" ;
   private final static String default_notification_channel_id = "default" ;
   @Override
   protected void onCreate (Bundle savedInstanceState) {
      super .onCreate(savedInstanceState) ;
      setContentView(R.layout. activity_main ) ;
      Button btnCreateNotification = findViewById(R.id. btnCreateNotification ) ;
      btnCreateNotification.setOnClickListener( new View.OnClickListener() {
         @Override
         public void onClick (View v) {
            Intent intent = new Intent(MainActivity. this, MainActivity. class ) ;
            PendingIntent contentIntent = PendingIntent. getActivity (MainActivity. this, 0 , intent , PendingIntent. FLAG_UPDATE_CURRENT ) ;
            NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(MainActivity. this, default_notification_channel_id )
               .setSmallIcon(R.drawable. ic_launcher_foreground )
               .setContentIntent(contentIntent)
               .setContentTitle( "Test" )
               .setContentText( "Hello! This is my first push notification" );
            NotificationManager mNotificationManager = (NotificationManager) getSystemService(Context. NOTIFICATION_SERVICE );
            if (android.os.Build.VERSION. SDK_INT >= android.os.Build.VERSION_CODES. O ) {
               int importance = NotificationManager. IMPORTANCE_HIGH ;
               NotificationChannel notificationChannel = new NotificationChannel( NOTIFICATION_CHANNEL_ID , "NOTIFICATION_CHANNEL_NAME" , importance) ;
               mBuilder.setChannelId( NOTIFICATION_CHANNEL_ID ) ;
               assert mNotificationManager != null;
               mNotificationManager.createNotificationChannel(notificationChannel) ;
            }
            assert mNotificationManager != null;
            mNotificationManager.notify(( int ) System. currentTimeMillis () ,
            mBuilder.build()) ;
         }
      }) ;
   }
}
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.tutorialspoint.com.notifyme" >
   <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