Flutter android_alarm_manager plugin doesnt run periodically

Question

Im trying to create background timer in Flutter, that will be called every n seconds. Calling AndroidAlarmManager.periodic should run printHello function every 2 seconds, bu

Answer 1

@kashlo, Add the following codes inside your main()

void funTimerMain() async  {

  // A few things that you can do with funTimerMain:

  // No 1. Do something you want, e.g.
  intCounter += 1;  // intCounter is a GLOBAL VARIABLE (Integer), which was initialized to 0
  print('intCounter: ' + intCounter.toString());

  // No 2. Use the following lines only if you use Redux to manage state
  // strCurPage is a GLOBAL VARIABLE (String) that stores which 'page' the user is currently navigating
  if (strCurPage == 'PageHome') {
    // storeHome is the Redux 'STORE' that keep track of the state of Page Home
    // The following line 'Refresh/Re-render' page Home (like a 'setState' in Page Home)
    // i.e. you can 'setState' page Home in an external event, like in this timer function
    storeHome.dispatch(Actions.Increment);
  }

  // No 3. Send a message to server every 5 seconds (Instead of 1 second!), using socket.io
  // timLastHeartBeat is a Global Variable (Integer) that was initialized to DateTime.now().millisecondsSinceEpoch;
  if (DateTime.now().millisecondsSinceEpoch - timLastHeartBeat > 5000) {
    socket.emit('HeartBeat', [intCounter]);
    timLastHeartBeat = DateTime.now().millisecondsSinceEpoch;
  }


  // recall this timer every 1 second
  new Future.delayed(new Duration(milliseconds: 1000), () async { 
    funTimerMain(); 
  }); 
}


// runApp!
runApp(MyApp());


// call the timer for the first time
funTimerMain();

Question 1: When will no. 1, 2, 3 in funTimerMain run? Ans 1: When the App is in foreground(i.e. user using the App), or When the App is in Background (i.e. user press Home button, or switch to another App).

Question 2: When will no. 1, 2 stopped to run? Ans 2: When the App is killed by the user, or by the Android System (e.g. killed by battery saving program)

Question 3: When will no. 3 stopped to run? Ans 3: Same as Ans 2, plus, when user turn off the screen. Starting from Android ? (I forgot the exact version), network access is not allowed when user turn off screen.

As you can see, the funTimerMain runs every 1 second (Or x seconds), but each task inside funTimerMain can be run every y seconds. (with y >= x, or better be y = Nx with N an integer)

When I first use this technique, I thought the efficiency would be terrible, but when I run the app in real mobile phone, I can't notice any delay in the mobile phone. So I think by setting an appropriate values of x and y, you can have a responsive app.

You may use 'await' inside funTimerMain as well, but remember, if the 'function after await' does not return, the timer is paused!