Repeating alarms with irregular intervals : Android tutorial

Program description:

This program will demo how to create alarms which will repeat at irregular intervals.
This program has one activity with one button, and a broadcast receiver.
On clicking the button, we will set an alarm for next 1 second, which triggers broadcast receiver.
Our program aim is to repeat next alarm at 2 seconds, next at 4 seconds, next at 8 seconds and so on.. For this requirement we can't use setRepeating() function of alarm manager.
We have to set the alarm manually in the receiver.

Once the first alarm (which was set for 1 second) is triggered, it will call broadcast receiver. In the receiver set alarm for next 2 seconds from that time. Which will again call same broadcast receiver after 2 seconds. Again set one more alarm for next 4 seconds in that receiver. For this we have to write a generic logic, because alarm has to repeat for n number of times.

First Activity:

package com.techpalle.b15_alarm_asg2;

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.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {
 AlarmManager am;
 Button b;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  am = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
  b = (Button) findViewById(R.id.button1);
  b.setOnClickListener(new OnClickListener() {
   @Override
   public void onClick(View v) {
    // TODO Auto-generated method stub
    Intent in = new Intent();
    in.setAction("com.techpalle.action.ALARM_INDEF");
    int i=1;
    in.putExtra("val", i);
    PendingIntent pi = PendingIntent.getBroadcast(
      getApplicationContext(), 
      0, 
      in, 
      0);
    am.set(AlarmManager.RTC_WAKEUP, 
      System.currentTimeMillis()+1000, 
      pi);
    
   }
  });
 }

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
  // Inflate the menu; this adds items to the action bar if it is present.
  getMenuInflater().inflate(R.menu.main, menu);
  return true;
 }
 
 @Override
 public boolean onOptionsItemSelected(MenuItem item) {
  // TODO Auto-generated method stub
  return super.onOptionsItemSelected(item);
 }

}

Broadcast receiver 
File name : AlarmRecvr.java

package com.techpalle.b15_alarm_asg2;

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.view.ViewDebug.FlagToString;
import android.widget.Toast;

public class AlarmRecvr extends BroadcastReceiver {
 //public static int i = 1;
 @Override
 public void onReceive(Context context, Intent intent) {
     int i = intent.getExtras().getInt("val");
     i = i*2;
     Toast.makeText(context, "Got", 0).show();
     Intent in = new Intent();
     in.setAction("com.techpalle.action.ALARM_INDEF");
     in.putExtra("val", i);
     PendingIntent pi = PendingIntent.getBroadcast(
       context, 0, in, PendingIntent.FLAG_UPDATE_CURRENT);
     AlarmManager am = (AlarmManager) context.getSystemService(context.ALARM_SERVICE);
     am.set(AlarmManager.RTC_WAKEUP, 
       System.currentTimeMillis()+(i*1000),
       pi);     
 }
}

xml file for first activity 
File name : 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"  
   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" >  
   <TextView  
     android:id="@+id/textView1"  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:text="@string/hello_world" />  
   <Button  
     android:id="@+id/button1"  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:layout_alignLeft="@+id/textView1"  
     android:layout_below="@+id/textView1"  
     android:layout_marginLeft="41dp"  
     android:layout_marginTop="70dp"  
     android:text="Start alarms.." />  
 </RelativeLayout>  

Manifest file
File name : AndroidManifest.xml

 <?xml version="1.0" encoding="utf-8"?>  
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"  
   package="com.techpalle.b15_alarm_asg2"  
   android:versionCode="1"  
   android:versionName="1.0" >  
   <uses-sdk  
     android:minSdkVersion="8"  
     android:targetSdkVersion="17" />  
   <application  
     android:allowBackup="true"  
     android:icon="@drawable/ic_launcher"  
     android:label="@string/app_name"  
     android:theme="@style/AppTheme" >  
     <activity  
       android:name="com.techpalle.b15_alarm_asg2.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="AlarmRecvr">  
       <intent-filter >  
         <action android:name="com.techpalle.action.ALARM_INDEF"/>  
       </intent-filter>  
     </receiver>  
   </application>  
 </manifest>  

Download complete code : Click to download

Android interview questions on Power manager and wake locks:
What is sleep mode? What will happen to CPU when LCD is turned off?
What are the two components that runs in Sleep mode also?
Every day night at 12 o clock I need to post some images to Facebook, in that case I will set repeating alarm for every day night 12 am. But to upload images I want to start service, how should I do this ?
What is the difference between Intent, Sticky Intent, and Pending Intent?