I have code to refresh data from server which I need to run even when screen is off. I tried to do this with an isolate:
static void isolateFunc(SendPort mainSendPort) async{
String _answer = "";
while(true){
Socket socket = await Socket.connect(ipAddress, port, timeout: Duration(seconds: 5));
socket.add(utf8.encode("connection test"));
socket.listen((List<int> event) {
_answer = utf8.decode(event);
});
socket.close();
await Future.delayed(Duration(seconds: 5));
}
}
This works fine when screen is on. But after switching off the screen it refreshs maybe for 5 times normally, then it refreshs for a few times each 30 sesconds(even when the delay is set to 5 seconds) and then it just stops. I am calling the isolate from initState like this:
#override
void initState() {
super.initState();
anotherRefresher();
ReceivePort recievePort = ReceivePort();
Isolate.spawn(isolateFunc, recievePort.sendPort);
}
Battery optimalisation in android settings is off. I do not understand this :/ Any ideas how to deal with this please?
After some time I found that, there is no way how to keep running dart code in the background without setting it as background or foreground process. Both Android and iOS will always restrict your code to increase battery life. Even turning off battery optimisation will not help. So to keep dart code running even when screen is off, you need to set up background or foreground process. For this you can do some platform native coding and connect it through platform channels or use plugins. Since I don't know Swift or Kotlin, I decided to find some plugins. I have tried more of them and after some time I can say that plugin flutter_background_service is one of the best. Or based on your needs you can find another plugins or try to code it by yourself. Wish you good luck :)
Related
I'm trying to build a video calling app with Agora, I need to show acceptance screen like WhatsApp when user calling, if the app is exited i need to show calling screen when user is calling, I tried lot of thing but nothing works, I trying to do i flutter and but there is nothing much information on this,Please help me
First things first. You need to learn about some concepts before delving into your solution. Actually there isn't an out of the box solution.
You need to use a couple of things together:
Use push notifications to "wake up" your app:
https://pub.dev/packages/firebase_messaging
To start your app using push notifications refers to this post:
https://stackoverflow.com/a/48405551/4335775
Use CallKit (IOS) or ConnectionServices (Android) to show the upcoming call screen. By the day of this answer there are only a few packages to handle these things, here is one that can handle both platforms:
https://pub.dev/packages/flutter_callkeep
If you want a completely different thing and need to run some background process, there are bunch whole of things you should know first. I suggest beginning here: https://flutter.dev/docs/development/packages-and-plugins/background-processes
Here is a usefull package to work with background processes that should be constantly running:
https://pub.dev/packages/background_fetch
Currently there are two packages which provides integration for agora.io:
https://pub.dev/packages/agora_rtc_engine (for Agora Real Time Communication, vídeo call included)
https://pub.dev/packages/agora_rtm for real-time messaging
I hope this can help you.
You can try WorkManager plugin.
You can register an call back function to the os when the app is closed.
const myTask = "syncWithTheBackEnd";
void main() {
Workmanager.initialize(callbackDispatcher);
Workmanager.registerOneOffTask(
"1",
myTask, //This is the value that will be returned in the callbackDispatcher
initialDelay: Duration(minutes: 5),
constraints: WorkManagerConstraintConfig(
requiresCharging: true,
networkType: NetworkType.connected,
),
);
runApp(MyApp());
}
void callbackDispatcher() {
Workmanager.executeTask((task) {
switch (task) {
case myTask:
print("this method was called from native!");
break;
case Workmanager.iOSBackgroundTask:
print("iOS background fetch delegate ran");
break;
}
//Return true when the task executed successfully or not
return Future.value(true);
});
}
Maybe this can help you.
The complete article medium article
There is a particular feature of this application, called Forest, I would like to emulate.
Basically you start a timer in the application and you are not to switch out from it.
This timer counts down if the application is in the foreground and/or when the screen is off.
There is a given grace period of approximately 10 seconds where a user can switch out of the app (i.e. press home button). If they do not return within the grace period, the timer ends and the user fails. Else the timer continues counting.
Basically the application has to check if it is the background. If it is, start a 10 second timer. Once this timer expire, set a bit such then when the app is back to foreground, the user continues/fails.
I am unsure how do this as reading the Flutter/Dart documentation, the lifecycle states available in Flutter is abstracted away from us. Would I have to run some background code or trigger an interrupt? I looked at the plugins available but they do not allow for triggers below 15 minutes. How is this achieved in native Android/iOS code?
You can use Android alarm manager. Through which you can run some background task when alarm triggered.
import 'package:android_alarm_manager/android_alarm_manager.dart';
void printHello() {
final DateTime now = new DateTime.now();
final int isolateId = Isolate.current.hashCode;
print("[$now] Hello, world! isolate=${isolateId} function='$printHello'");
}
main() async {
final int helloAlarmID = 0;
runApp(...);
await AndroidAlarmManager.periodic(const Duration(minutes: 1), helloAlarmID, printHello);
}
prints 'Hello world' for every minute roughly even if app ends.
PS: example code provided above was taken from plugin example.
I'm new to Dart/Flutter and would like to build a simple app where a LinearProgressBar gets updated every second.
Without getting too much into the actual code, I have the following setup working.
A function that calculates the progress, based on passed time.
A LinearProgressBar showing the progress.
A periodic Timer recalculating the progress and updating the progress bar every second.
I debugprint 'tick' every time, the recalculation is done.
Everything is working as expected with one exception. The 'tick' keeps getting printed when I move the app in the background on my Android device.
On native Android, I would cancel my periodic Timer when the 'onPause' event is triggered.
Is there something similar in Flutter? All I could find was 'initState' and 'dispose'. Dispose, however, does not get called when moving the app to background.
I don't want the timer to keep ticking in the background.
On my research, I found this Stack Overflow question onresume-and-onpause-for-widgets-on-flutter. It's answer suggests using TickerProviderStateMixin.
I used it the following way.
class _BarItemState extends State<BarItem> with SingleTickerProviderStateMixin {
Ticker ticker;
num progress = 1.0;
#override
void initState() {
super.initState();
ticker = createTicker((duration) => setState(() {
debugPrint('tick');
progress = duration.inSeconds / 30;
}))
..start();
}
// other stuff omitted
}
It is working, but I'm still not satisfied.
The reason is, that the ticker callback is getting now called every few milliseconds instead of once a second. This seems to me like a waste of resources (I don't need a smooth animation), ... am I overcomplicating things?
Even if it seems that I don't need it for my use case, I still would like to know:
How to handle the onPause/onResume events on my own?
You can override the didChangeAppLifecycleState of the WidgetBindingObserver interface to receive notifications for app lifecycle changes.
There's sample code in this page
You can use lifecycle channel from SystemChannels.
Example:
SystemChannels.lifecycle.setMessageHandler((msg){
debugPrint('SystemChannels> $msg');
});
Output:
I/flutter ( 3672): SystemChannels> AppLifecycleState.paused
I/flutter ( 3672): SystemChannels> AppLifecycleState.resumed
I have being upgrading an application to use the new Mobile Android GNSK but I have noticed that using the new MusicID-Stream is a little bit tricky. If the "identifyAlbumAsync" method get executed before the "audioProcessStart" method(since this need to be executed in a different thread), the application just crashes. In the Gracenote Demo application, the "audioProcessStart" method is continuously running so there is no need to synchronize its execution with the "identifyAlbumAsync" method call. Is it the way it is supposed to be used? It will be convenient if the application didn't crashed at least when the methods are not executed in order. Also in our application, we don't want to have the "audioProcessStart" method continuously like it is done in the demo application. We only want to run the "audioProcessStart" method when the user request identification and when the song playing gets identified , we want to stop the audio processing by calling "audioProcessStop". Is there an easy way to do this? Right now, we are getting the Thread where "identifyAlbumAsync" is running to sleep for 2 seconds in order to make sure that the Thread where the "audioProcessStart" method is supposed to run has time to get executed. Thank you in advance for your prompt response
In the upcoming 1.2 release, IGnMusicIdStreamEvents includes a callback that signals audio-processing has started, and an ID can be synced with this, e.g.:
#Override
public void musicIdStreamProcessingStatusEvent( GnMusicIdStreamProcessingStatus status, IGnCancellable canceller ) {
if (GnMusicIdStreamProcessingStatus.kStatusProcessingAudioStarted.compareTo(status) == 0) {
try {
gnMusicIdStream.identifyAlbumAsync();
} catch (GnException e) { }
}
}
Thanks for the feedback, you're right about this issue. Unfortunately right now sleeping is the best solution. But we are adding support for an explicit sync event in an upcoming release, please stay tuned.
I can't seem to remove the listener for the update event for geolocation on Android.
I wanna stop the Geolocation on deactivate:
NativeApplication.nativeApplication.addEventListener(Event.DEACTIVATE, onAppDeactivate);
private function onAppDeactivate(e:Event):void {
if (Geolocation.isSupported) {
if (geolocation != null) {
geolocation.removeEventListener(GeolocationEvent.UPDATE, onGeolocationUpdate);
geolocation.setRequestedUpdateInterval(0);
geolocation = null;
}
}
}
I started with just removing the listener, but since that didn't work I also tried removing the geolocation all together. Still no luck..
Any hints?
I had an app that uses Geolocation too, and if what you want is to save the battery from draining fast, you have to call the geolocation.setRequestedUpdateInterval(INTERVAL_MILLIS) method with a high value for INTERVAL_MILLIS (in my case i use 60000 that is 1 min).
But as the (documentation) says, the OS will decide the update interval for the GPS, ant the value we pass serves a a "hint" to the update interval.
And specifically on Android, the GPS icon will stay on as long as you have the GPS enabled (and it will consume power) but will no drain you battery fast as the update interval will be high.
So the best thing you can do is actually request a large update interval when you app deactivates.