Actually I was trying to implement background process (fetch data from api) even the app is terminated in my flutter project how can I achieve in both Android & iOS platforms.
Have you ever wanted to execute Dart code in the background—even if your app wasn’t the currently active app?
The mechanism for this feature involves setting up an isolate.
Isolates are Dart’s model for multithreading, though an isolate
differs from a conventional thread in that it doesn’t share memory
with the main program. You’ll set up your isolate for background
execution using callbacks and a callback dispatcher.
Example
but if you want do that when app terminated, you will have to wakeup app through Workmanager or some another approach like sending firebase push notification or wakeup app in scheduled time with flutter alarm manager or something like that
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Hi I instantiated an isolate for my data layer above my main app, above runApp()
I wonder what will happen when the app is minimised, will the isolate be closed. Do isolates time out anyway...
Has anyone got experience of this in a live app?
As from Flutter's happy recommendeations page:
There are a of couple ways to incorporate background processing into your mobile app. One way is through a Dart isolate. With a Dart
isolate, you can create a separate thread to run tasks concurrently in
the background.
Another way to incorporate background processing is through the
WorkManager plugin. With this plugin, you can enable persistent
headless execution of Dart code. Your tasks remain scheduled through
app restarts and system reboots.
so the answer is yes, you can achieve running dart code in the background with Dart isolates, but consider also using the workManager package.
I tested the situation proposed, and the isolates were working(simply setup a timer which logs some random message to console) even if app is minimised. If the app is killed by user or by OS, isolates will be killed as well. And yes you can spawn an isolate before runApp(). If the isolate is required to return some data to the main isolate, I recommend making the main() function async and wait(await) for the completion. Flutter will not render the UI until everything before runApp() is completed without error.
I have a question about how best to structure a background process in a Flutter mobile app that can be triggered in a number of ways.
This background process has to run a web API call, or series of web API calls. The process will take 1 to 5 seconds to complete.
I want the process to be initiated when any of the following occurs:
When the app first starts
When the user initiates a 'refresh' by clicking on a button in the UI
Every hour
Any suggestions on how to structure this in a Flutter app?
You should take a look at this package: https://pub.dev/packages/flutter_background_service
It can run code in background and/or in foreground either on iOs and Android.
Background and foreground are run in isolate, so you should use mechanism provide by package to exchange data between your application and background/foreground.
I am using agora_rtc_engine for video calling.
I have tested the Firebase background message but the documentation mentions:
Since the handler runs in its own isolate outside your applications
context, it is not possible to update application state or execute any
UI impacting logic. You can however perform logic such as HTTP
requests, IO operations (updating local storage), communicate with
other plugins etc.
Source https://firebase.flutter.dev/docs/messaging/usage/
How I can display incoming call screen when Firebase notification arrived in the background when App is killed?
I also use callkeep. It shows phone's default calling screen but when I click on answer call it starts the call. I am not able to navigate to specific screen.
Thanks.
Here is something that you can try - using the CallKeepPerformAnswerCallAction event you can bring your app to foreground using bringtoforeground
Is there a way to automatically resume a flutter app from a paused or inactive lifecycle state with a background service?
Similar to when the WhatsApp app received a call while it was paused or inactive.
No, you can not simply wake up the app from a service. This would open the door for all kinds of spam apps and security risks. You need to specifically register it as VOIP app using CallKit or something like SIP on Android to receive incoming calls.
For other things you can use push notifications but that won't start your app. The user always has to click on the notification that you display.
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
The app can only be waked up with explicit commands. The user must hit the button. And there are ways to handle the input, messages may pass parameters, you can save the previous state in the database or shared preferences, etc.
Is it possible to use connectivity plugin in background process?
I don't know how to call dart code in background there is little about this in docs.
I need this functionality to sync offline data with backend whenever there is a connection wether app is in foreground or background and app is in killed state like the way Whatsapp syncs messages.
You can use existing plugins for background execution (on android & ios usually in a roughly 15 minute interval)
https://pub.dev/packages/background_fetch
There is also a article dedicated to using isolates for background executions
https://flutter.dev/docs/development/packages-and-plugins/background-processes
https://medium.com/flutter/executing-dart-in-the-background-with-flutter-plugins-and-geofencing-2b3e40a1a124