Android AlarmManager

Android AlarmManager allows you to access system alarm.

By the help of Android AlarmManager in android, you can schedule your application to run at a specific time in the future. It works whether your phone is running or not.

The Android AlarmManager holds a CPU wake lock that provides guarantee not to sleep the phone until broadcast is handled.

Android AlarmManager Example

Let's see a simple AlarmManager example that runs after a specific time provided by user.

activity_main.xml

You need to drag only a edittext and a button as given below.

File: activity_main.xml

1. <?xml version="1.0" encoding="utf-8"?>  
2. <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
3.     xmlns:app="http://schemas.android.com/apk/res-auto"  
4.     xmlns:tools="http://schemas.android.com/tools"  
5.     android:layout_width="match_parent"  
6.     android:layout_height="match_parent"  
7.     tools:context="example.javatpoint.com.alarmmanager.MainActivity">  
8.   
9.     <Button  
10.         android:id="@+id/button"  
11.         android:layout_width="wrap_content"  
12.         android:layout_height="wrap_content"  
13.         android:text="Start"  
14.         android:layout_alignParentBottom="true"  
15.         android:layout_centerHorizontal="true"  
16.         android:layout_marginBottom="103dp" />  
17.   
18.     <EditText  
19.         android:id="@+id/time"  
20.         android:layout_width="wrap_content"  
21.         android:layout_height="wrap_content"  
22.         android:layout_alignParentTop="true"  
23.         android:layout_centerHorizontal="true"  
24.         android:layout_marginTop="22dp"  
25.         android:ems="10" />  
26. </RelativeLayout>  

---

Activity class

The activity class starts the alarm service when user clicks on the button.

File: MainActivity.java

1. package example.javatpoint.com.alarmmanager;  
2.   
3. import android.app.AlarmManager;  
4. import android.app.PendingIntent;  
5. import android.content.Intent;  
6. import android.support.v7.app.AppCompatActivity;  
7. import android.os.Bundle;  
8. import android.view.View;  
9. import android.widget.Button;  
10. import android.widget.EditText;  
11. import android.widget.Toast;  
12.   
13. public class MainActivity extends AppCompatActivity {  
14.     Button start;  
15.     @Override  
16.     protected void onCreate(Bundle savedInstanceState) {  
17.         super.onCreate(savedInstanceState);  
18.         setContentView(R.layout.activity_main);  
19.         start= findViewById(R.id.button);  
20.   
21.         start.setOnClickListener(new View.OnClickListener() {  
22.             @Override  
23.             public void onClick(View view) {  
24.                 startAlert();  
25.             }  
26.         });  
27.     }  
28.   
29.     public void startAlert(){  
30.         EditText text = findViewById(R.id.time);  
31.         int i = Integer.parseInt(text.getText().toString());  
32.         Intent intent = new Intent(this, MyBroadcastReceiver.class);  
33.         PendingIntent pendingIntent = PendingIntent.getBroadcast(  
34.                 this.getApplicationContext(), 234324243, intent, 0);  
35.         AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);  
36.         alarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis()  
37.                 + (i * 1000), pendingIntent);  
38.         Toast.makeText(this, "Alarm set in " + i + " seconds",Toast.LENGTH_LONG).show();  
39.     }  
40. }  

Let's create BroadcastReceiver class that starts alarm.

File: MyBroadcastReceiver.java

1. package example.javatpoint.com.alarmmanager;  
2.   
3. import android.content.BroadcastReceiver;  
4. import android.content.Context;  
5. import android.content.Intent;  
6. import android.media.MediaPlayer;  
7. import android.widget.Toast;  
8.   
9. public class MyBroadcastReceiver extends BroadcastReceiver {  
10.     MediaPlayer mp;  
11.     @Override  
12.     public void onReceive(Context context, Intent intent) {  
13.         mp=MediaPlayer.create(context, R.raw.alarm);  
14.         mp.start();  
15.         Toast.makeText(context, "Alarm....", Toast.LENGTH_LONG).show();  
16.     }  
17. }  

---

File: AndroidManifest.xml

You need to provide a receiver entry in AndroidManifest.xml file.

1. <receiver android:name="MyBroadcastReceiver" >  
2. </receiver>  

Let's see the full code of AndroidManifest.xml file.

1. <?xml version="1.0" encoding="utf-8"?>  
2. <manifest xmlns:android="http://schemas.android.com/apk/res/android"  
3.     package="example.javatpoint.com.alarmmanager">  
4.   
5.     <application  
6.         android:allowBackup="true"  
7.         android:icon="@mipmap/ic_launcher"  
8.         android:label="@string/app_name"  
9.         android:roundIcon="@mipmap/ic_launcher_round"  
10.         android:supportsRtl="true"  
11.         android:theme="@style/AppTheme">  
12.         <activity android:name=".MainActivity">  
13.             <intent-filter>  
14.                 <action android:name="android.intent.action.MAIN" />  
15.   
16.                 <category android:name="android.intent.category.LAUNCHER" />  
17.             </intent-filter>  
18.         </activity>  
19.         <receiver android:name="MyBroadcastReceiver" >  
20.         </receiver>  
21.     </application>  
22.   
23. </manifest>  

Output: