Firefox OS alarm to wake up closed app

Question

Looking at documentation it looks like the alarm api can be used to restart an app at a certain time

I changed the code from boilerplate example in this way

    // Alarm API
var alarmDate = new Date("Jul 8, 2014 19:35:00"),
    addAlarm = document.querySelector("#add-alarm"),
    alarmDisplay = document.querySelector("#alarm-display");
if (addAlarm) {
    addAlarm.onclick = function () {
        var alarm = navigator.mozAlarms.add(alarmDate, "honorTimezone", {
            "optionalData" : "I am data"
        });

        alarm.onsuccess = function () {

       var request = window.navigator.mozApps.getSelf();
   request.onsuccess = function() {
    navigator.mozSetMessageHandler("alarm", function (mozAlarm) { 
      request.result.launch();
      alert("alarm fired: " + JSON.stringify(mozAlarm.data)); 
    });
};

request.onerror = function() {
     alert("Error: " + request.error.name);
 };
};

The code seems to bring up the app only if the app is running (even in background) BUT not if the app is closed.

Is this the intended behaviour? Any way to restart a closed app?

Also is it possible to bring up the app in foreground and make it unlock the screen?

Thanks

UPDATE Just as a clarification, the issue appears when the system memory load requires killing an app. Android provides a way to schedule restart of an app (while iOS, afaik, does not...). It would be useful if an app could be restarted at the moment in which it's required. That's also saving a lot of battery...

Answer 1

Your code is wrong: the setMessageHandler is created in the onsuccess handler of mozAlarms.add. That code will not be executed when the alarm fires. You need to always add the listener on app startup.

Here's some simple code that adds and responds to an alarm (from app-days-dhaka).

var request = navigator.mozAlarms.add(new Date((+new Date()) + 30000), 'ignoreTimezone', {
  type: 'yolo'
});

console.log('setting to', new Date((+new Date()) + 30000) + '')

request.onsuccess = function() {
  console.log('success');
}

request.onerror = function() {
  console.error('err');
}

navigator.mozSetMessageHandler('alarm', function() {
  console.log('alarm');
  launchSelf();
});

function launchSelf() {
  var request = window.navigator.mozApps.getSelf();
  request.onsuccess = function() {
    if (request.result) {
      request.result.launch();
    }
  };
}

Open the app (this will set the alarm), then close the app immediately (via long press on home). After 30 seconds the app will open again automatically.