How to set multiple alarms using alarm manager in android

How to set multiple alarms using alarm manager in android

In Android, you can set multiple alarms using the AlarmManager class along with PendingIntent to schedule intents at specified times. Each alarm is uniquely identified by a requestCode in the PendingIntent, which allows you to manage multiple alarms simultaneously. Here's a step-by-step guide to set multiple alarms using AlarmManager:

Step 1: Create a Broadcast Receiver

First, create a BroadcastReceiver that will receive the alarm trigger. This receiver will handle what happens when the alarm is triggered.

public class AlarmReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { // Handle alarm trigger action here // You can perform actions like showing notifications, starting services, etc. // Example: show a notification NotificationHelper.showNotification(context, "Alarm Triggered", "Alarm Message"); } }

Step 2: Register the BroadcastReceiver in Manifest

Ensure that you register your BroadcastReceiver in the AndroidManifest.xml file with an intent filter for the action "android.intent.action.BOOT_COMPLETED" to handle device reboots.

<receiver android:name=".AlarmReceiver" android:enabled="true" android:exported="false"> <intent-filter> <action android:name="android.intent.action.BOOT_COMPLETED" /> </intent-filter> </receiver>

Step 3: Set Alarms Using AlarmManager

Now, in your activity or service where you want to set alarms, use AlarmManager to schedule multiple alarms.

public class MainActivity extends AppCompatActivity { private static final int ALARM_REQUEST_CODE_1 = 1; private static final int ALARM_REQUEST_CODE_2 = 2; private AlarmManager alarmManager; private PendingIntent pendingIntent1; private PendingIntent pendingIntent2; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE); // Create an intent for AlarmReceiver Intent alarmIntent = new Intent(this, AlarmReceiver.class); alarmIntent.setAction("com.example.android.alarm.ACTION_ALARM"); // Create PendingIntent for each alarm with unique requestCode pendingIntent1 = PendingIntent.getBroadcast(this, ALARM_REQUEST_CODE_1, alarmIntent, PendingIntent.FLAG_UPDATE_CURRENT); pendingIntent2 = PendingIntent.getBroadcast(this, ALARM_REQUEST_CODE_2, alarmIntent, PendingIntent.FLAG_UPDATE_CURRENT); // Set Alarm 1: Trigger at a specific time (e.g., 9 AM) Calendar calendar1 = Calendar.getInstance(); calendar1.setTimeInMillis(System.currentTimeMillis()); calendar1.set(Calendar.HOUR_OF_DAY, 9); calendar1.set(Calendar.MINUTE, 0); alarmManager.setExact(AlarmManager.RTC_WAKEUP, calendar1.getTimeInMillis(), pendingIntent1); // Set Alarm 2: Trigger after a specific interval (e.g., 1 hour) long intervalMillis = 60 * 60 * 1000; // 1 hour in milliseconds long triggerAtMillis = System.currentTimeMillis() + intervalMillis; alarmManager.setInexactRepeating(AlarmManager.RTC_WAKEUP, triggerAtMillis, intervalMillis, pendingIntent2); } }

Explanation

  • BroadcastReceiver: AlarmReceiver handles the action when the alarm triggers. Customize onReceive() method to perform actions like showing notifications.

  • AlarmManager: Manages alarms set by the app. Use setExact() for precise time-based alarms and setInexactRepeating() for alarms that repeat at intervals.

  • PendingIntent: Represents an intent to be executed later. Use getBroadcast() to obtain a PendingIntent for a BroadcastReceiver.

  • Unique RequestCodes: Each alarm uses a unique requestCode (ALARM_REQUEST_CODE_1, ALARM_REQUEST_CODE_2) in PendingIntent to distinguish between different alarms.

Additional Considerations

  • Permissions: Ensure that your app has necessary permissions declared in the AndroidManifest.xml, such as android.permission.SET_ALARM for setting alarms.

  • Handling Device Reboots: Register your BroadcastReceiver to receive BOOT_COMPLETED broadcasts to re-establish alarms after device restarts.

  • Power Management: Use AlarmManager.RTC_WAKEUP to wake up the device when the alarm triggers, especially for time-sensitive tasks.

By following these steps, you can effectively set multiple alarms using AlarmManager in your Android application, each with unique functionalities and triggers as per your app's requirements. Adjust the times, intervals, and actions handled in AlarmReceiver according to your specific use case.

Examples

  1. How to set a single alarm using AlarmManager in Android?

    AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE); Intent intent = new Intent(this, AlarmReceiver.class); PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0); long triggerAtMillis = System.currentTimeMillis() + 60000; // 1 minute later alarmManager.set(AlarmManager.RTC_WAKEUP, triggerAtMillis, pendingIntent);

    Description: This code sets a single alarm to trigger 1 minute later using the AlarmManager. The AlarmReceiver will handle the alarm.

  2. How to set multiple alarms with different IDs using AlarmManager?

    for (int i = 0; i < 5; i++) { AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE); Intent intent = new Intent(this, AlarmReceiver.class); PendingIntent pendingIntent = PendingIntent.getBroadcast(this, i, intent, 0); long triggerAtMillis = System.currentTimeMillis() + (i + 1) * 60000; // i minutes later alarmManager.set(AlarmManager.RTC_WAKEUP, triggerAtMillis, pendingIntent); }

    Description: This code sets five alarms, each triggering one minute apart. The unique ID for each alarm is used to differentiate them.

  3. How to create a repeating alarm using AlarmManager in Android?

    AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE); Intent intent = new Intent(this, AlarmReceiver.class); PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0); long intervalMillis = AlarmManager.INTERVAL_FIFTEEN_MINUTES; alarmManager.setInexactRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), intervalMillis, pendingIntent);

    Description: This sets a repeating alarm that triggers every 15 minutes using setInexactRepeating.

  4. How to cancel an existing alarm using AlarmManager?

    AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE); Intent intent = new Intent(this, AlarmReceiver.class); PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0); alarmManager.cancel(pendingIntent);

    Description: This code cancels an existing alarm by calling cancel on the AlarmManager with the same PendingIntent.

  5. How to set an alarm that triggers at a specific time using AlarmManager?

    Calendar calendar = Calendar.getInstance(); calendar.set(Calendar.HOUR_OF_DAY, 14); // 2 PM calendar.set(Calendar.MINUTE, 0); calendar.set(Calendar.SECOND, 0); AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE); Intent intent = new Intent(this, AlarmReceiver.class); PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0); alarmManager.setExact(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), pendingIntent);

    Description: This code sets an alarm to trigger at 2 PM using setExact.

  6. How to set an alarm that triggers at boot using AlarmManager?

    public class BootReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { if (Intent.ACTION_BOOT_COMPLETED.equals(intent.getAction())) { setAlarms(context); } } private void setAlarms(Context context) { // Code to set alarms here } }

    Description: This code sets alarms when the device boots by registering a BootReceiver.

  7. How to set an alarm with a custom time interval using AlarmManager?

    long customInterval = 2 * 60 * 1000; // 2 minutes AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE); Intent intent = new Intent(this, AlarmReceiver.class); PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0); alarmManager.setInexactRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), customInterval, pendingIntent);

    Description: This code sets a repeating alarm with a custom interval of 2 minutes.

  8. How to show a notification when an alarm triggers?

    public class AlarmReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE); NotificationCompat.Builder builder = new NotificationCompat.Builder(context, "AlarmChannel") .setSmallIcon(R.drawable.ic_alarm) .setContentTitle("Alarm") .setContentText("Your alarm has gone off!") .setPriority(NotificationCompat.PRIORITY_HIGH); notificationManager.notify(0, builder.build()); } }

    Description: This code displays a notification when the alarm triggers, informing the user.

  9. How to set an alarm using a unique tag for each alarm?

    for (int i = 0; i < 5; i++) { String tag = "Alarm" + i; AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE); Intent intent = new Intent(this, AlarmReceiver.class); PendingIntent pendingIntent = PendingIntent.getBroadcast(this, i, intent, PendingIntent.FLAG_UPDATE_CURRENT); long triggerAtMillis = System.currentTimeMillis() + (i + 1) * 60000; alarmManager.set(AlarmManager.RTC_WAKEUP, triggerAtMillis, pendingIntent); }

    Description: This sets multiple alarms with unique tags to manage them easily.

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