Why is my Alarm not working?

Question

On my Android app I am trying to run a task every 3 minutes, and if the CPU is asleep then it should wake up and run my task; my task is called CheckTask and is a Runnable. I know AlarmManager is what I need and I have been trying to get it working but the OnReceive() method is never executed. Here is the relevant code below, please tell me what is wrong so I can fix it and get it working.

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.charles.sitechecker"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="18"
android:targetSdkVersion="18"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.VIBRATE"/>
<uses-permission android:name="android.permission.FLASHLIGHT"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="com.android.alarm.permission.SET_ALARM"/>
<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme">
    <activity
        android:name="com.charles.sitechecker.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>
    <service
        android:name=".LocalService"
        android:enabled="true"
        android:exported="false">
    <intent-filter>
        <action android:name="com.charles.sitechecker.LocalService" />
    </intent-filter>
    </service>
    <receiver
        android:name="com.charles.sitechecker.Alarm"
        android:enabled="true"/>
</application>

Alarm.java

package com.charles.sitechecker;

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

public class Alarm extends BroadcastReceiver
{

    private MainActivity mainActivity;
    private AlarmManager aManager;

    public Alarm()
    {

    }

    Alarm(MainActivity mainActivity)
    {
        this.mainActivity = mainActivity;
        aManager = (AlarmManager)mainActivity.getSystemService(Context.ALARM_SERVICE);
    }

    void scheduleAlarm()
    {
        Intent intent = new Intent(mainActivity, Alarm.class);
        PendingIntent pIntent = PendingIntent.getBroadcast(mainActivity, 1, intent, PendingIntent.FLAG_UPDATE_CURRENT);
        aManager.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, System.currentTimeMillis(), 180000, pIntent);
    }

    public void onReceive(Context context, Intent intent)
    {
        Runnable task = new CheckTask(mainActivity);
        task.run();
    }

}

LocalService.java

package com.charles.sitechecker;

import android.app.Notification;
import android.app.Service;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.IBinder;

public class LocalService extends Service
{

    public void onCreate()
    {
        Notification n = MainActivity.checkTask.mainActivity.notifier.sendOngoingNotification("SiteChecker", "Sleeping", -1);
        startForeground(-1, n);
        Alarm alarm = new Alarm(MainActivity.checkTask.mainActivity);
        alarm.scheduleAlarm();
    }

    public void onDestroy()
    {
        super.onDestroy();
    }

    public IBinder onBind(Intent intent)
    {
        return null;
    }

    public int onStartCommand(Intent intent, int flags, int startId)
    {
        return START_STICKY;
    }

}

Answer 1

an example class to set alarm in mainactivity:

public void setRepeatingAlarm()
{

     Intent intent = new Intent(this, ReceiveAlarm.class);
      PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0,
        intent, PendingIntent.FLAG_CANCEL_CURRENT);
      am.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(),
        (*time_in_milis to repeat*), pendingIntent);
}

Broadcast Receiver:

public class ReceiveAlarm extends BroadcastReceiver {


     @Override
     public void onReceive(Context context, Intent intent) {         
         context.startService(new Intent(context, InService.class));
     }
}

Intent service class example:

 public class InService extends IntentService
    {
        public InService() {
            super("InService");
            // TODO Auto-generated constructor stub
        }

    @Override
    protected void onHandleIntent(Intent intent) {

//do your thing here
}

}

Declare your broadcast receiver / service class in manifest inside tags

<receiver android:name="ReceiveAlarm" />
<service android:name="InService"></service>

Try this.