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

<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" >

    <EditText
        android:id="@+id/time"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginTop="28dp"
        android:ems="10"
        android:hint="Number of seconds"
        android:inputType="numberDecimal" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/time"
        android:layout_below="@+id/time"
        android:layout_marginRight="60dp"
        android:layout_marginTop="120dp"
        android:text="Start" />

</RelativeLayout>

Activity class

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

File: MainActivity.java

package com.example.alarmexample;

import android.app.Activity;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {
Button b1;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		b1=(Button) findViewById(R.id.button1);
	
		b1.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				startAlert();
			}
		});
	
}	public void startAlert() {
		EditText text = (EditText) 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();
	}

}

Let's create BroadcastReceiver class that starts alarm.

File: MyBroadcastReceiver.java

package com.example.alarmexample;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.media.MediaPlayer;
import android.widget.Toast;

public class MyBroadcastReceiver extends BroadcastReceiver {
	MediaPlayer mp;
	@Override
	public void onReceive(Context context, Intent intent) {
		mp=MediaPlayer.create(context, R.raw.alrm	);
		mp.start();
		Toast.makeText(context, "Alarm....", Toast.LENGTH_LONG).show();
	}
}

File: AndroidManifest.xml

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

        <receiver android:name="MyBroadcastReceiver" >
        </receiver>

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

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.alarmexample"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="16" />

    <uses-permission android:name="android.permission.VIBRATE" />


    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.alarmexample.MainActivity"
            android:label="@string/app_name" >
            <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>

download this android example