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. <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
2.     xmlns:tools="http://schemas.android.com/tools"  
3.     android:layout_width="match_parent"  
4.     android:layout_height="match_parent"  
5.     tools:context=".MainActivity" >  
6.   
7.     <EditText  
8.         android:id="@+id/time"  
9.         android:layout_width="wrap_content"  
10.         android:layout_height="wrap_content"  
11.         android:layout_alignParentLeft="true"  
12.         android:layout_alignParentTop="true"  
13.         android:layout_marginTop="28dp"  
14.         android:ems="10"  
15.         android:hint="Number of seconds"  
16.         android:inputType="numberDecimal" />  
17.   
18.     <Button  
19.         android:id="@+id/button1"  
20.         android:layout_width="wrap_content"  
21.         android:layout_height="wrap_content"  
22.         android:layout_alignRight="@+id/time"  
23.         android:layout_below="@+id/time"  
24.         android:layout_marginRight="60dp"  
25.         android:layout_marginTop="120dp"  
26.         android:text="Start" />  
27.   
28. </RelativeLayout>  

---

Activity class

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

File: MainActivity.java

1. package com.example.alarmexample;  
2.   
3. import android.app.Activity;  
4. import android.app.AlarmManager;  
5. import android.app.PendingIntent;  
6. import android.content.Intent;  
7. import android.os.Bundle;  
8. import android.view.View;  
9. import android.view.View.OnClickListener;  
10. import android.widget.Button;  
11. import android.widget.EditText;  
12. import android.widget.Toast;  
13.   
14. public class MainActivity extends Activity {  
15. Button b1;  
16.   
17.     @Override  
18.     protected void onCreate(Bundle savedInstanceState) {  
19.         super.onCreate(savedInstanceState);  
20.         setContentView(R.layout.activity_main);  
21.         b1=(Button) findViewById(R.id.button1);  
22.       
23.         b1.setOnClickListener(new OnClickListener() {  
24.               
25.             @Override  
26.             public void onClick(View v) {  
27.                 // TODO Auto-generated method stub  
28.                 startAlert();  
29.             }  
30.         });  
31.       
32. }   public void startAlert() {  
33.         EditText text = (EditText) findViewById(R.id.time);  
34.         int i = Integer.parseInt(text.getText().toString());  
35.         Intent intent = new Intent(this, MyBroadcastReceiver.class);  
36.         PendingIntent pendingIntent = PendingIntent.getBroadcast(  
37.                                       this.getApplicationContext(), 234324243, intent, 0);  
38.         AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);  
39.         alarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis()  
40.                                       + (i * 1000), pendingIntent);  
41.         Toast.makeText(this, "Alarm set in " + i + " seconds",Toast.LENGTH_LONG).show();  
42.     }  
43.   
44. }  

Let's create BroadcastReceiver class that starts alarm.

File: MyBroadcastReceiver.java

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

---

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="com.example.alarmexample"  
4.     android:versionCode="1"  
5.     android:versionName="1.0" >  
6.   
7.     <uses-sdk  
8.         android:minSdkVersion="8"  
9.         android:targetSdkVersion="16" />  
10.   
11.     <uses-permission android:name="android.permission.VIBRATE" />  
12.   
13.   
14.     <application  
15.         android:allowBackup="true"  
16.         android:icon="@drawable/ic_launcher"  
17.         android:label="@string/app_name"  
18.         android:theme="@style/AppTheme" >  
19.         <activity  
20.             android:name="com.example.alarmexample.MainActivity"  
21.             android:label="@string/app_name" >  
22.             <intent-filter>  
23.                 <action android:name="android.intent.action.MAIN" />  
24.   
25.                 <category android:name="android.intent.category.LAUNCHER" />  
26.             </intent-filter>  
27.         </activity>  
28.   
29.         <receiver android:name="MyBroadcastReceiver" >  
30.         </receiver>  
31.     </application>  
32.   
33. </manifest>  

---

Output: