Android alarmmanager after reboot

Android AlarmManager after reboot

I have a set of alarms that I need to keep after reboot. I’ve tried using on an boot receiver but they won’t start again. I’m not sure if I understand the boot receiver and how to then restart all the alarms. I already have one receiver for my notifications, but don’t know whether I can use the same receiver or if I need a new one?

Could anyone point me to any good tutorials or help me out?

with NotificationMenu being the notifications, which is why I’m using the AlarmManager

Answers

I’m not sure if I understand the boot receiver and how to then restart all the alarms.

Just call your code to call setRepeating() (or whatever) on AlarmManager .

For example, in this sample project, PollReceiver is set to receive BOOT_COMPLETED . In onReceive() , it reschedules the alarms:

1) In your element:

Create Boot Receiver using following code :

In your Manifest, register this Broadcast receiver :

And don’t forget to add permission in AndroidManifest.xml :

I can’t think why you wouldn’t want to create a new process, but if you really don’t want to, then execve(«reboot»,0,0) will run reboot , replacing the current process. You’ll need to include .

I’m assuming this is available on Mac OS; it should be on all POSIX platforms.

UPDATE

It appears that Mac OS has a reboot system call. reboot(RB_AUTOBOOT); might do what you want. Or it might trash your hard drive. Be very careful when trying to work against the operating system like this.

The documentation about the AlarmManager says that :

Registered alarms are retained while the device is asleep (and can optionally wake the device up if they go off during that time), but will be cleared if it is turned off and rebooted.

It seems that the AlarmClock included by default by Android does work even after a reboot.

On way to keep your alarms working after a reboot, is to start your application on boot completed and set up all the alams again with the AlarmManager. (In fact you may want to just setup your alarms using a Broadcast, not start your app)

Here is a StackOverflow question dealing about lunching an app on startup.

You wan also check out how the default AlarmClock does this by reading from the source. You can read and download it from here

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Руководство по Android AlarmManager

Информация о проекте: Мета-информация о проекте. Версия платформы: Android API Level 10.
IDE: Eclipse Helios Service Release 2
Эмулятор: Android 4.1

Обязательное условие: предварительные знания инфраструктуры приложений Android и приемника Intent Broadcast.

AlarmManager:

AlarmManager имеет доступ к системным службам сигнализации. С помощью AlarmManager вы можете запланировать выполнение кода в будущем. Объект AlarmManager не может быть создан напрямую, однако его можно получить, вызвав Context.getSystemService (Context.ALARM_SERVICE) . AlarmManager всегда регистрируется с намерением. Когда срабатывает сигнал тревоги, намерение, зарегистрированное в AlarmManager, транслируется системой автоматически. Это намерение запускает целевое приложение, если оно не запущено. Рекомендуется использовать AlarmManager, когда вы хотите, чтобы код вашего приложения запускался в определенное время, даже если ваше приложение в данный момент не запущено. Для других операций синхронизации следует использовать обработчик, потому что он прост в использовании. Обработчик рассматривается в другом уроке.

метод	Описание
поставил()	Расписание будильника на один раз.
setInexactRepeating ()	Графики тревоги с неточным повторением. Время запуска не следует строгим ограничениям.
setRepeating ()	Расписание будильника с точным повторением времени.
установить время()	Устанавливает время настенных часов системы.
setTimeZone ()	Устанавливает часовой пояс системы по умолчанию.

Проверьте документацию AlarmManager для получения дополнительной информации.

В этом уроке мы научимся создавать одноразовый таймер и повторяющийся таймер, а также отменять повторяющийся таймер. Здесь таймер и будильник были использованы взаимозаменяемо, но в этом учебном контексте оба они имеют одинаковое значение.

Пример кода:

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Android AlarmManager after reboot

I have a set of alarms that I need to keep after reboot. I’ve tried using on an boot receiver but they won’t start again. I’m not sure if I understand the boot receiver and how to then restart all the alarms. I already have one receiver for my notifications, but don’t know whether I can use the same receiver or if I need a new one?

Could anyone point me to any good tutorials or help me out?

with NotificationMenu being the notifications, which is why I’m using the AlarmManager

Answers

I’m not sure if I understand the boot receiver and how to then restart all the alarms.

Just call your code to call setRepeating() (or whatever) on AlarmManager .

For example, in this sample project, PollReceiver is set to receive BOOT_COMPLETED . In onReceive() , it reschedules the alarms:

1) In your element:

Create Boot Receiver using following code :

In your Manifest, register this Broadcast receiver :

And don’t forget to add permission in AndroidManifest.xml :

I can’t think why you wouldn’t want to create a new process, but if you really don’t want to, then execve(«reboot»,0,0) will run reboot , replacing the current process. You’ll need to include .

I’m assuming this is available on Mac OS; it should be on all POSIX platforms.

UPDATE

It appears that Mac OS has a reboot system call. reboot(RB_AUTOBOOT); might do what you want. Or it might trash your hard drive. Be very careful when trying to work against the operating system like this.

The documentation about the AlarmManager says that :

Registered alarms are retained while the device is asleep (and can optionally wake the device up if they go off during that time), but will be cleared if it is turned off and rebooted.

It seems that the AlarmClock included by default by Android does work even after a reboot.

On way to keep your alarms working after a reboot, is to start your application on boot completed and set up all the alams again with the AlarmManager. (In fact you may want to just setup your alarms using a Broadcast, not start your app)

Here is a StackOverflow question dealing about lunching an app on startup.

You wan also check out how the default AlarmClock does this by reading from the source. You can read and download it from here

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Using AlarmManager like a pro

Feb 2, 2019 · 3 min read

All of us must have used AlarmManager in some way in our projects but there a lot of times when our alarms get cancelled or there are bugs in the implementation. Today we will learn what all measures we should take to make sure that all our alarms are set correctly. We will also understand what all scenarios we should consider whenever we are using the AlarmManager.

Firstly let’s get the basics righ t . There are two types of alarms that you can set. You can either set a one time alarm or a repeating alarm. Let’s quickly have a look at both of these alarms.

For non repeating alarms we just have to specify at what time we need the alarm. The following alarm will fire after 1 min.

For repeating alarms, we have to first set at what time we need the alarm and then the duration after which the alarm should repeat itself. The following alarm will fire everyday. AlarmManager.INTERVAL_DAY is nothing but the time in milliseconds for a day, instead you can also specify any time of your choice in milliseconds.

So it is very easy to set these alarms but now let’s discuss the cases when these alarms get cancelled or behave in an unusual manner.

All alarms get cancelled when the phone reboots

By default all alarms get cancelled when a device shuts down. To tackle this we need to set the alarms again when the user restarts their device. Let’s have a look how this is done.

The above permission needs to be added in the manifest so that the app can receive the ACTION_BOOT_COMPLETED broadcast after the system finishes booting.

Don’t forget to add the receiver in the manifest with the action BOOT_COMPLETED. If you are wondering what android:enabled=”false” is it simply means that the receiver will not be called unless it is explicitly enabled in the app.

The above code enables the receiver. You should preferably add it in the first activity of your app.

The BroadcastReceiver above gets called whenever the user reboots their device. Here we will set the alarm again but the important thing is we can’t use the values passed through the intent to set the alarm. This is because these values will be null when the system reboots. We need to pass values from a permanent source of memory like a SQL database.

All alarms get cancelled when the system time is changed

Another case when the Alarms get cancelled is when the user changes their system time or date from the settings. Let’s see what we can do to tackle this situation.

Firstly we need to register a receiver in the manifest with the action TIME_SET.

The following BroadcastReceiver will get called every time the user changes the system time. You just have to set the alarms again in the onReceive.

All past Alarms are fired immediately

When we are setting our alarms it is very important to check that the time that we are setting the alarm is not of the past because these alarms will get fired as soon as they are set. A simple check such as the following will ensure that no past alarms are fired.

These were some of the points that you should keep in mind if you are using the AlarmManager to set alarms for may be showing periodic notifications once a day.

Here is the link of the sample project that I made for this story. Feel free to check it out.

Thanks for reading! If you enjoyed this story, please click the 👏 button and share to help others! Feel free to leave a comment 💬 below. Have feedback? Let’s connect on Twitter .

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Repeat Alarm Example In Android Using AlarmManager

1. AlarmManager in Android

AlarmManager is a class in Android allows you to access device system alarm service. Using AlarmManager, you can schedule to execute certain piece of code a particular time. Let us dive into details of AlarmManager specifics:

• AlarmManager runs outside the lifetime of your application. Once an alarm is scheduled, it will invoke even when your application is not running or in sleep mode.
• An scheduled alarm will execute unless it is stopped explicitly by calling cancel() method, or until device reboots.
• All scheduled alarms will be stopped when device reboots. This means, you need to re-schedule them explicitly when device boot completes.
• AlarmManger fires an Intent at given intervals. This can be used along with broadcast receivers to start a service to perform network operations.
• AlarmManager is different form java Timer and TimerTask.

2. Setting Repeat Alarm

Android supports two clock types for alarm service; elapsed real time and real time clock (RTC). Elapsed real time uses the time since device last booted. Real time clock (RTC) uses UTC time for alarm service clock. RTC is most commonly used for setting alarm service in android. The following example, using RTC to schedule alarm.

The application using a single activity containing three buttons. One button is for starting an alarm service, another to cancel scheduled alarm. The third button is to start the alarm at specified calendar time. For example, if you have set a time for your birthday reminder. It will invoke at 10:30 PM and will repeat on every 30 mins.

Let us have a look into our activity layout file (my_activity.xml)

3. Defining Alarm BroadcastReceiver

In this example, we are associating alarm service with broadcast receiver. Alarm service will invoke this receiver on scheduled time. For the sake of simplicity we are just showing an toast to user for each time the alarm is invoked. You may write your logic to start a service or download task.

4. Schedule & Cancel Alarm

In the above two steps we have defined activity layout and alarm broadcast receiver. Let us have a look into MainActivity.java file. Inside MyActivity class, we have defined three simple methods start(), stop() and startAt10(). The start() method schedule the alarm, cancel() method cancel the scheduled alarm, and startAt!0() method will start the alarm at 10:30 PM with a fixed 20 minutes interval.

5. Re-Starting Alarm Service on Device Reboot

As discussed earlier, once an alarm service is started, it execute until it is explicitly stopped or until device reboots. This means that, if your device is restarted then your alarm is stopped. To avoid such situation, you have to restart your alarm service as soon as device boot completes. Below code snippet will help you to start alarm service once device reboots.

6. Declaring Application Manifest

To start your alarm on device reboot, you have to register your above declared DeviceBootReciever class in your application manifest. This also need android.permission.RECEIVE_BOOT_COMPLETED

7. Download Source Code

Download Complete source code from GitHub

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