Develop Reference

Kill Background Job on Active App State React Native

I am having problems stopping a background action running in my android app. Basically, the way I am using it in this way:
1- I use an appState hook that lets me know when the app is in foreground or background.
2- When the appState Turns to 'background' I start a background job using BackgroundJob.start() from 'react-native-background-action'.
3-When the appState turns to 'active' (comes back to foreground). I use BackgroundJob.stop()
The problem happens when I kill the app, cause when I kill the app and I lose the reference from the background job I started before, so every time kill the app I add another job to the background making the app work bad, so my question basically is:
Did you face the same problem? If you did how did you solve it? If not, do you have another way to solve the problem?
I use the background job cause my app has a speech recognition functionality that gets triggered by a wake word, and it needs to listen when the app is in the background.
useEffect(() => {
const startBackgroundListening = async () => {
await BackgroundJob.start(backgroundListening, backgroundOptions);
};
const stopPorcupine = async () => {
await porcupineRef.current?.stop();
porcupineRef.current?.delete();
};
if (currentAppState === 'background') {
if (isLoggedIn) {
if (isNotificationShowed === false) {
handleNotification(
i18n.t('closingWarning'),
i18n.t('closingWarningText'),
);
uiStore.updateIsNotificationShowed(true);
}
if ((isRecord || isCall || isSms || isAlarm) && isBackgroundListeningRunning.current === false) {
//start background listenning
startBackgroundListening();
isBackgroundListeningRunning.current = true;
}
}
} else if (currentAppState === 'active') {
//stop and delete background listenning in case there is one
stopPorcupine();
BackgroundJob.stop();
isBackgroundListeningRunning.current = false;
}
}, [currentAppState]);

The react-native-background-action documentation (https://www.npmjs.com/package/react-native-background-actions) states that "If you call stop() on background no new tasks will be able to be started! Don't call .start() twice, as it will stop performing previous background tasks and start a new one. If .start() is called on the background, it will not have any effect." If your concern was that multiple Background tasks would run simultaneously and cause bad app performance, the documentation shows calling .start() stops any previous background tasks, so you should be fine!

Android Back Button on a Progressive Web Application closes de App

Can a "pure" HTML5/Javascript (progressive) web application intercept the mobile device back button in order to avoid the App to exit?
This question is similar to this one but I want to know if it is possible to achieve such behavior without depending on PhoneGap/Ionic or Cordova.

While the android back button cannot be directly hooked into from within a progressive web app context, there exists a history api which we can use to achieve your desired result.
First up, when there's no browser history for the page that the user is on, pressing the back button immediately closes the app.
We can prevent this by adding a previous history state when the app is first opens:
window.addEventListener('load', function() {
window.history.pushState({}, '')
})
The documentation for this function can be found on mdn:
pushState() takes three parameters: a state object, a title (which is currently ignored), and (optionally) a URL[...] if it isn't specified, it's set to the document's current URL.
So now the user has to press the back button twice. One press brings us back to the original history state, the next press closes the app.
Part two is we hook into the window's popstate event which is fired whenever the browser navigates backwards or forwards in history via a user action (so not when we call history.pushState).
A popstate event is dispatched to the window each time the active history entry changes between two history entries for the same document.
So now we have:
window.addEventListener('load', function() {
window.history.pushState({}, '')
})
window.addEventListener('popstate', function() {
window.history.pushState({}, '')
})
When the page is loaded, we immediately create a new history entry, and each time the user pressed 'back' to go to the first entry, we add the new entry back again!
Of course this solution is only so simple for single-page apps with no routing. It will have to be adapted for applications that already use the history api to keep the current url in sync with where the user navigates.
To do this, we will add an identifier to the history's state object. This will allow us to take advantage of the following aspect of the popstate event:
If the activated history entry was created by a call to history.pushState(), [...] the popstate event's state property contains a copy of the history entry's state object.
So now during our popstate handler we can distinguish between the history entry we are using to prevent the back-button-closes-app behaviour versus history entries used for routing within the app, and only re-push our preventative history entry when it specifically has been popped:
window.addEventListener('load', function() {
window.history.pushState({ noBackExitsApp: true }, '')
})
window.addEventListener('popstate', function(event) {
if (event.state && event.state.noBackExitsApp) {
window.history.pushState({ noBackExitsApp: true }, '')
}
})
The final observed behaviour is that when the back button is pressed, we either go back in the history of our progressive web app's router, or we remain on the first page seen when the app was opened.

#alecdwm, that is pure genius!
Not only does it work on Android (in Chrome and the Samsung browser), it also works in desktop web browsers. I tested it on Chrome, Firefox and Edge on Windows, and it's likely the results would be the same on Mac. I didn't test IE because eew. Even if you're mostly designing for iOS devices that have no back button, it's still a good idea to ensure that Android (and Windows Mobile... awww... poor Windows Mobile) back buttons are handled so that the PWA feels much more like a native app.
Attaching an event listener to the load event didn't work for me, so I just cheated and added it to an existing window.onload init function I already had anyhow.
Keep in mind that it might frustrate users who would actually want to really Go Back to whatever web page they were looking at before navigating to your PWA while browsing it as a standard web page. In that case, you can add a counter and if the user hits back twice, you can actually allow the "normal" back event to happen (or allow the app to close).
Chrome on Android also (for some reason) added an extra empty history state, so it took one additional Back to actually go back. If anyone has any insight on that, I'd be curious to know the reason.
Here's my anti-frustration code:
var backPresses = 0;
var isAndroid = navigator.userAgent.toLowerCase().indexOf("android") > -1;
var maxBackPresses = 2;
function handleBackButton(init) {
if (init !== true)
backPresses++;
if ((!isAndroid && backPresses >= maxBackPresses) ||
(isAndroid && backPresses >= maxBackPresses - 1)) {
window.history.back();
else
window.history.pushState({}, '');
}
function setupWindowHistoryTricks() {
handleBackButton(true);
window.addEventListener('popstate', handleBackButton);
}

This approach has a couple of improvements over existing answers:
Allows the user to exit if they press back twice within 2 seconds: The best duration is debatable but the idea of allowing an override option is common in Android apps so it's often the correct approach.
Only enables this behaviour when in standalone (PWA) mode: This ensures the website keeps behaving as the user would expect when within an Android web browser and only applies this workaround when the user sees the website presented as a "real app".
function isStandalone () {
return !!navigator.standalone || window.matchMedia('(display-mode: standalone)').matches;
}
// Depends on bowser but wouldn't be hard to use a
// different approach to identifying that we're running on Android
function exitsOnBack () {
return isStandalone() && browserInfo.os.name === 'Android';
}
// Everything below has to run at page start, probably onLoad
if (exitsOnBack()) handleBackEvents();
function handleBackEvents() {
window.history.pushState({}, '');
window.addEventListener('popstate', () => {
//TODO: Optionally show a "Press back again to exit" tooltip
setTimeout(() => {
window.history.pushState({}, '');
//TODO: Optionally hide tooltip
}, 2000);
});
}

i did not want to use native javascript functions to handle this inside of a react app, so i scoured solutions
that used react-router or react-dom-router, but in the end, up against a deadline, native js is
what got it working. Added the following listeners inside inside componentDidMount() and setting the history
to an empty state
window.addEventListener('load', function() {
window.history.pushState({}, '')
})
window.addEventListener('popstate', function() {
window.history.pushState({}, '')
})
this worked fine on the browser, but was still not working in the PWA on mobile
finally a colleague found out that triggering the history actions via code is what somehow initiated the listeners
and voila! everything fell in place
window.history.pushState(null, null, window.location.href);
window.history.back();
window.history.forward();

In my case, I had a SPA with different drawers on that page and I want them to close when User hits back button..
you can see different drawers in the image below:
I was managing states(eg open or close) of all drawers at a central location (Global state),
I added the followin code to a useEffect hook that runs only once on loading of web app
// pusing initial state on loading
window.history.pushState(
{ // Initial states of drawers
bottomDrawer,
todoDetailDrawer,
rightDrawer,
},
""
);
window.addEventListener("popstate", function () {
//dispatch to previous drawer states
// dispatch will run when window.history.back() is executed
dispatch({
type: "POP_STATE",
});
});
and here is what my dispatch "POP_STATE" was doing,
if (window.history.state !== null) {
const {
bottomDrawer,
rightDrawer,
todoDetailDrawer,
} = window.history.state; // <- retriving state from window.history
return { // <- setting the states
...state,
bottomDrawer,
rightDrawer,
todoDetailDrawer,
};
It was retriving the last state of drawers from window.history and setting it to current state,
Now the last part, when I was calling window.history.pushState({//object with current state}, "title", "url eg /RightDrawer") and window.history.back()
very simple,
window.history.pushState({//object with current state}, "title", "url eg /RightDrawer") on every onClick that opens the drawer
&
window.history.back() on every action that closes the drawer.

How to handle force close event in ionic app?

I want to close my app when user force close.
Any event arise for force close in ionic application ?
Any plugin for force close event handling in ionic app ?
example:
A common piece of functionality for native mobile applications is the ability to logged out if the user closes the application(force stop/force close).
How can this be achieved for a Cordova / Ionic / PhoneGap ?

Put the following code accordingly to your angular.run configuration, and that's it. You can even add some checks, for example using a boolean value in a Service or a check to the current state to decide if prompt to the user the closing app notice or not.
.run(function($ionicPlatform, $ionicPopup) {
$ionicPlatform.onHardwareBackButton(function () {
if(true) { // your check here
$ionicPopup.confirm({
title: 'System warning',
template: 'are you sure you want to exit?'
}).then(function(res){
if( res ){
navigator.app.exitApp();
}
})
}
})
});
More...

Is it really posible to close a PhoneGap App?

I have searched all over the web and found different ways of closing a PhoneGap App. I tested all of them and none work. At least on Android.
Question:
Is it possible (By Feb 2014) to have a close button in a PhoneGap App on Android?
Thanks
This doesn't work:
function CloseApp() {
if (confirm('Close this App?')){
if (navigator.app) {
navigator.app.exitApp();
}else if (navigator.device) {
navigator.device.exitApp();
}
}
}

Is
navigator.app.exitApp()
really killing/closing the android app with phonegap?
I use cordova and have the same issue. Above mentioned code is just putting the app into background - I checked the running tasks (android task manager) after above code got executed by the app.

I am confused on why you want a button to close the app. Android already has a back button when clicked enough times will take the user back to the phone's main screen. There is also a home button that takes the user out of an app. Once, out of the app the user can "kill" the app through a task manager.

navigator.app.exitApp()
works and I use it in all my cordova apps. Check the rest of your code.
As ejwill said, having a "close" button is a bad idea. On Android I call exitApp when the user is the home page of my app and he presses the backbutton:
function onDeviceReady() {
document.addEventListener("backbutton", onBackKey, false);
}
function onBackKey( event ) {
var l = window.location.toString();
var parts = l.split('#/'); // this works only if you are using angularjs
var page = parts[1];
if (page == 'home') {
navigator.app.exitApp();
} else {
// do something else... one option is:
navigator.app.backHistory();
}
}
My 2c.

What happens to JavaScript execution (settimeout, etc.) when iPhone/Android goes to sleep?

I have a jQuery Mobile web app which targets iOS and Android devices. A component of the application is a background task, which periodically checks for a.) changes to local data and b.) connectivity to the server. If both are true, the task pushes the changes.
I'm using a simple setTimeout()-based function to execute this task. Each failure or success condition calls setTimeout() on the background task, ensuring that it runs on 30 second intervals. I update a status div with the timestamp of the last task runtime for debugging purposes.
In any desktop browser, this works just fine; however, on iOS or Android, after some period of time, the task stops executing. I'm wondering if this is related to the power conservation settings of the devices--when iOS enters stand-by, does it terminate JavaScript execution? That is what appears to happen.
If so, what is the best way to resume? Is there an on-wake event which I can hook into? If not, what other options are there which don't involve hooking into events dependent on user interaction (I don't want to bind the entire page to a click event just to restart the background task).

Looks like Javascript execution is paused on MobileSafari when the browser page isn't focused. It also seems if setInterval() events are late, they are simply fired as soon as the browser is focused. This means we should be able to keep a setInterval() running, and assume the browser lost/regained focus if the setInterval function took much longer than usual.
This code alerts after switching back from a browser tab, after switching back from another app, and after resuming from sleep. If you set your threshold a bit longer than your setTimeout(), you can assume your timeout wouldn't finish if this fires.
If you wanted to stay on the safe side: you could save your timeout ID (returned by setTimeout) and set this to a shorter threshold than your timeout, then run clearTimeout() and setTimeout() again if this fires.
<script type="text/javascript">
var lastCheck = 0;
function sleepCheck() {
var now = new Date().getTime();
var diff = now - lastCheck;
if (diff > 3000) {
alert('took ' + diff + 'ms');
}
lastCheck = now;
}
window.onload = function() {
lastCheck = new Date().getTime();
setInterval(sleepCheck, 1000);
}
</script>
Edit: It appears this can sometimes trigger more than once in a row on resume, so you'd need to handle that somehow. (After letting my android browser sleep all night, it woke up to two alert()s. I bet Javascript got resumed at some arbitrary time before fully sleeping.)
I tested on Android 2.2 and the latest iOS - they both alert as soon as you resume from sleep.

When the user switches to another app or the screen sleeps, timers seem to pause until the user switches back to the app (or when the screen awakens).
Phonegap has a resume event you can listen to instead of polling for state (as well as a pause event if you want to do things before it is out of focus). You start listening to it after deviceReady fires.
document.addEventListener("deviceready", function () {
// do something when the app awakens
document.addEventListener('resume', function () {
// re-create a timer.
// ...
}, false);
}, false);
I use angular with phonegap and I have a service implemented that manages a certain timeout for me but basically you could create an object that sets the timer, cancels the timer and most importantly, updates the timer (update is what is called during the 'resume' event).
In angular I have a scopes and root scope that I can attach data to, my timeout is global so I attach it to root scope but for the purpose of this example, I'll simply attach it to the document object. I don't condone that because you need should apply it to some sort of scope or namespace.
var timeoutManager = function () {
return {
setTimer: function (expiresMsecs) {
document.timerData = {
timerId: setTimeout(function () {
timeoutCallback();
},
expiresMsecs),
totalDurationMsecs: expiresMsecs,
expirationDate: new Date(Date.now() += expiresMsecs)
};
},
updateTimer: function () {
if (document.timerData) {
//
// Calculate the msecs remaining so it can be used to set a new timer.
//
var timerMsecs = document.timerData.expirationDate - new Date();
//
// Kill the previous timer because a new one needs to be set or the callback
// needs to be fired.
//
this.cancelTimer();
if (timerMsecs > 0) {
this.setTimer(timerMsecs);
} else {
timeoutCallback();
}
}
},
cancelTimer: function () {
if (document.timerData && document.timerData.timerId) {
clearTimeout(document.timerData.timerId);
document.timerData = null;
}
}
};
};
You could have the manager function take a millisecond parameter instead of passing it into set, but again this is modeled somewhat after the angular service I wrote. The operations should be clear and concise enough to do something with them and add them to your own app.
var timeoutCallback = function () { console.log('timer fired!'); };
var manager = timeoutManager();
manager.setTimer(20000);
You will want to update the timer once you get the resume event in your event listener, like so:
// do something when the app awakens
document.addEventListener('resume', function () {
var manager = timeoutManager();
manager.updateTimer();
}, false);
The timeout manager also has cancelTimer() which can be used to kill the timer at any time.

You can use this class github.com/mustafah/background-timer based on #jlafay answer , where you can use as follow:
coffeescript
timer = new BackgroundTimer 10 * 1000, ->
# This callback will be called after 10 seconds
console.log 'finished'
timer.enableTicking 1000, (remaining) ->
# This callback will get called every second (1000 millisecond) till the timer ends
console.log remaining
timer.start()
javascript
timer = new BackgroundTimer(10 * 1000, function() {
// This callback will be called after 10 seconds
console.log("finished");
});
timer.enableTicking(1000, function(remaining) {
// This callback will get called every second (1000 millisecond) till the timer ends
console.log(remaining);
});
timer.start();
Hope it helps, Thank you ...

You should use the Page Visibility API (MDN) which is supported just about everywhere. It can detect if a page or tab has become visible again and you can then resume your timeouts or carry out some actions.