Alarm manager is inexact in periodic method (exact= true is not working).

[P-B1101]

System info

Issue occurs on:Android
Plugin name: Alarm Manager Plus
Plugin version: 1.2.0
Flutter doctor output:

Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 2.5.1, on Microsoft Windows [Version 10.0.19043.1237], locale fa-IR)
[!] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    X Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.       
      See https://flutter.dev/docs/get-started/install/windows#android-setup for more details.
[√] Chrome - develop for the web
[√] Visual Studio - develop for Windows (Visual Studio Community 2019 16.8.6)
[√] Android Studio (version 2020.3)
[√] VS Code (version 1.60.2)
[√] Connected device (4 available)

! Doctor found issues in 1 category.

Steps to Reproduce

final now = DateTime.now();
    final tomorrow = DateTime(
      now.year,
      now.month,
      now.day + 1,
      23,
    );
    final duration = Duration(days: 1);
    final result = await AndroidAlarmManager.periodic(
      duration,
      DAILY_ALARM_ID,
      _showDailyNotificationForAndroid,
      exact: true,
      startAt: tomorrow,
      wakeup: true,
      rescheduleOnReboot: true,
    );

static Future<void> _showDailyNotificationForAndroid() async {
   /// show notification or what ever
  }

Logs

[√] Flutter (Channel stable, 2.5.1, on Microsoft Windows [Version 10.0.19043.1237], locale fa-IR)
    • Flutter version 2.5.1 at C:\FlutterSdk\flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision ffb2ecea52 (2 weeks ago), 2021-09-17 15:26:33 -0400
    • Engine revision b3af521a05
    • Dart version 2.14.2

[!] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    • Android SDK at C:\AndroidSdk
    • Platform android-30, build-tools 30.0.3
    • ANDROID_HOME = C:\AndroidSdk
    • ANDROID_SDK_ROOT = C:\AndroidSdk
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 11.0.10+0-b96-7249189)
    X Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.
      See https://flutter.dev/docs/get-started/install/windows#android-setup for more details.

[√] Chrome - develop for the web
    • Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

[√] Visual Studio - develop for Windows (Visual Studio Community 2019 16.8.6)
    • Visual Studio at C:\Program Files (x86)\Microsoft Visual Studio\2019\Community
    • Visual Studio Community 2019 version 16.8.31019.35
    • Windows 10 SDK version 10.0.18362.0

[√] Android Studio (version 2020.3)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin can be installed from:
       https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
       https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 11.0.10+0-b96-7249189)

[√] VS Code (version 1.60.2)
    • VS Code at C:\Users\asus\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension version 3.26.0

[√] Connected device (4 available)
    • SM G955F (mobile) • 988a1b323750355946 • android-arm64  • Android 9 (API 28)
    • Windows (desktop) • windows            • windows-x64    • Microsoft Windows [Version 10.0.19043.1237]
    • Chrome (web)      • chrome             • web-javascript • Google Chrome 94.0.4606.61
    • Edge (web)        • edge               • web-javascript • Microsoft Edge 94.0.992.31

! Doctor found issues in 1 category.

The Problem is when I set alarm like the one in above, it maybe work for first or second time but it would be trigger with 3 minute delay or skip a day or once I get reminder with 12 hours delay!!!!
There is this note in alarm manager doc. is this considered?!

Note: Beginning with API 19 (Build.VERSION_CODES.KITKAT) alarm delivery is inexact: the OS will shift alarms in order to minimize wakeups and battery use. There are new APIs to support applications which need strict delivery guarantees; see setWindow(int, long, long, android.app.PendingIntent) and setExact(int, long, android.app.PendingIntent). Applications whose targetSdkVersion is earlier than API 19 will continue to see the previous behavior in which all alarms are delivered exactly when requested.

Extra Information (Edited)

There is some case that the alarm goes off for greater good and if I reboot my phone, it will rescheduled.

[vbuberen]

@mhadaily I would like to pick it up and work on it

[mhadaily]

go ahead @vbuberen

[vbuberen]

@P-B1101 I believe that #496 fixes the issue, so I would like to ask you to test your app using version from PR in same conditions, but with additional allowWhileIdle parameter.

[P-B1101]

ok, I will test it.

[P-B1101]

@vbuberen I did test it and the problem with inexact is gone (thank you).
there is one more problem. when I schedule an periodic alarm with one day duration for period , I only get one alarm.
my application scenario is that when the app is launch, I get list of works that need to be done in specific time. so first I cancel old alarm with specific work Id and then reschedule new one with the same id. if I start app for like 5 times It seems to be ok and everything is fine but when I launch app after a day (the works are daily) in the logs I see this line 'cancel: broadcast receiver not found' that says there is no alarm for specific work id!!!!! and then new alarm set (with the same id). so if I do not open app for like 2 days all alarms are gone for good.

PS: Because I have three kind of works (that may have same id) id did concat work id with some static number like this
final id = int.parse('112$workId');

[vbuberen]

Good news about issue with inexact.

As to a new one - could I ask you to open a new issue? I guess it will be another issue with repetitive alarms, like #323. Or, if you can add your info there.

As to your list of works - are you sure that it is something suitable for AlarmManager and not for WorkManager?
https://community.commonsware.com/t/workmanager-vs-alarm-manager/413/2

[filippo-biondi]

I still have trouble with periodic alarms being inexact even when I schedule them with exact=true (I also tested with the example code changing the oneShot alarm with a periodic one). From the code here I see that exact periodic alarm are scheduled with setRepeating but the android documentation state that "Note: as of API 19, all repeating alarms are inexact".
Also from the code it seems that the the parameter allowWhileIdle is unused in the case of a periodic alarm (but I haven't test it).