How to implement Alarm Manager in android?

This example demonstrates how do I implement alarm manager 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:id="@+id/button"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Start"
      android:layout_alignParentBottom="true"
      android:layout_centerHorizontal="true"
      android:layout_marginBottom="103dp" />
   <EditText
      android:id="@+id/time"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignParentTop="true"
      android:layout_centerHorizontal="true"
      android:layout_marginTop="22dp"
      android:ems="10" />
</RelativeLayout>
Step 3 − Add the following code to src/MainActivity.java
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
   Button start;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      start = findViewById(R.id.button);
      start.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View view) {
            startAlert();
         }
      });
   }
   public void startAlert() {
      EditText text = findViewById(R.id.time);
      int i = Integer.parseInt(text.getText().toString());
      Intent intent = new Intent(this, MyBroadcastReceiver.class);
      PendingIntent pendingIntent = PendingIntent.getBroadcast(this.getApplicationContext(), 234324243, intent, 0);
      AlarmManager alarmManager = (AlarmManager)getSystemService(ALARM_SERVICE);
      alarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + (i * 1000), pendingIntent);
      Toast.makeText(this, "Alarm set in " + i + " seconds", Toast.LENGTH_LONG).show();
   }
}
Step 4 − Create a java class naming BroadcastReceiver and add the following code −
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.media.MediaPlayer;
import android.widget.Toast;
class MyBroadcastReceiver extends BroadcastReceiver {
   MediaPlayer mp;
   @Override
   public void onReceive(Context context, Intent intent) {
      mp=MediaPlayer.create(context, R.raw.alarm);
      mp.start();
      Toast.makeText(context, "Alarm....", Toast.LENGTH_LONG).show();
   }
}
Step 5 − 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>
      <receiver android:name="MyBroadcastReceiver" ></receiver>
   </application>
</manifest>
Step 6 − Click file → New → Android Resource Directory, From the New resource directory, select “raw” from Resource type and click okay. Download an alarm ringtone, copy and paste it in the raw folder on your project. Naming the alarm ringtone file is really important.
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.