Using alarms : Android tutorial

Program description:

This program will demo how to create alarms with broadcast receiver.
This program has one activity and one static broadcast receiver. Activity has a button, on clicking that we will set an alarm which will expire after 5 seconds from now. Once alarm is triggered it will send a broadcast with action "com.techpalle.action.ALARM_RECEIVER".
Once broadcast receiver is triggered, it will show a toast message "alarm tirggered".

In order to send a broadcast by using alarms, here we will use pending intents.

Pending intent: It is used to perform intent operations at future point of time on our behalf by some one else (mostly by alarm manager or notification manager).

Broadcast will be send after 5 seconds from the time of button click. It will be send by alarm manager. Since we are not sending broadcast immediately, and it is sent after 5 seconds. So our intent to send broadcast will be pending till then. That's why it is called as pending intent.

Steps to do this alarm program with broadcast receiver in android:
1. Create a broadcast receiver that will be triggered/ called after 5 seconds.
2. Come to activity java file, Create alarm manager object by using getSystemService() method.
3. Create intent to send a broadcast.
4. Create pending intent to shoot a broadcast from above created intent.
5. set the alarm for next 5 seconds by using alarm manager and pass pending intent.

First Activity:

package com.techpalle.b15_alarms;

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

public class MainActivity extends Activity {
 Button b;
 AlarmManager am;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 b = (Button) findViewById(R.id.button1);
 //step1 : create alarm manager
 am = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
 b.setOnClickListener(new OnClickListener() {
 @Override
 public void onClick(View v) {
 //a. create intent
 Intent in = new Intent();
 in.setAction("com.techpalle.action.ALARM_RECEIVER");
 //b. create pending intent
 PendingIntent pi = PendingIntent.getBroadcast(
 getApplicationContext(), 
 0, 
 in, 
 0);
 //c. set alarm for 5 seconds.
 am.set(AlarmManager.RTC_WAKEUP, 
 System.currentTimeMillis()+5000, 
 pi);
 
 
 }
 });
 }
}

Broadcast receiver 
File name : AlarmRecvr.java

package com.techpalle.b15_alarms;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;

public class AlarmRecvr extends BroadcastReceiver {
 @Override
 public void onReceive(Context context, Intent intent) {
 Toast.makeText(context, "Got the alarm..", 0).show();
 }
}

xml file for first activity 
File name : activity_main.xml

  xmlns:tools="http://schemas.android.com/tools" 
 android:layout_width="match_parent" 
 android:layout_height="match_parent" 
 android:paddingBottom="@dimen/activity_vertical_margin" 
 android:paddingLeft="@dimen/activity_horizontal_margin" 
 android:paddingRight="@dimen/activity_horizontal_margin" 
 android:paddingTop="@dimen/activity_vertical_margin" 
 tools:context=".MainActivity" > 
 

Manifest file
File name : AndroidManifest.xml

  
  package="com.techpalle.b15_alarms" 
 android:versionCode="1" 
 android:versionName="1.0" > 
  android:minSdkVersion="8" 
 android:targetSdkVersion="17" /> 
  android:allowBackup="true" 
 android:icon="@drawable/ic_launcher" 
 android:label="@string/app_name" 
 android:theme="@style/AppTheme" > 
  android:name="com.techpalle.b15_alarms.MainActivity" 
 android:label="@string/app_name" > 
  
  
  
  
  
  
  
  
  
  
  
  

Download complete code : Click to download

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