Isolates and Event Loops - Flutter in Focus
Why Stack Overflow recommends it
Stack Overflow users link it when answering questions about Dart's single-threaded model, async behaviour, event loop ordering and when to use isolates for heavy work.
Recommended by 8 people across 8 different months, 2019 to 2023.
What it is
A short episode from the official Flutter team's Flutter in Focus series, presented by Andrew Brogdon, explaining how Dart's isolates and event loop work. It sets up the ideas behind Futures, Streams and background work in Dart and Flutter apps.
What people said
Strong rec bitinerant · 2023-02 · Stack Overflow · on “What is a Future and how do I use it?”
If you haven't dealt with futures in another programming language, it will take some time to grasp the concepts. I found Google's Flutter in Focus video series invaluable: ☐1. Isolates and Event Loops [this video] ; ☐2. Futures [LINK] ; ☐3. Streams [LINK] ; ☐4. Async/Await [LINK] ; ☐5. Generators [LINK]
Recommends Traufvihal · 2019-10 · Stack Overflow · on “fetch data with flutter Receiver: null error”
You are using both approaches for future handling, .then callbacks and async and await. Try the following, you can wrap these around try/catch blocks for error handling. Future<List<ArticleModal>> getLists() async { lists = new List(); var response = await http.get('bins/ut9kq'); // a switch may be used for a wider range of codes if (response.statusCode == 200) { var decodedResponse = json.decode(response.body); print(decodedResponse); //if response is a collection var listAricleModal = (decodedResponse as List).map((collectionElement) => ArticleModal.fromJson(collectionElement)).toList(); return listAricleModal; } //Your future is an empty collection return []; } And to properly answer your
Recommends Mohamed Elrashid · 2020-01 · Stack Overflow · on “Flutter: setState() doesn't execute until the enclosing function returns”
Event Loop There is something called Event Loop Event Loop process Events in order You have two events in order Event A => Click => by the User 0.onPressed: () { 1.setState(() { 3. i++ 4. Mark as widget dirty 5. Add to the global dirty widgets list }); 6.i++ }); Event B => Vsync signal => provided by the OS 7. check dirty widgets list 8. repaint More Here a YouTube video from Flutter in Focus series Isolates and Event Loops [this video] by flutter team member Andrew Brogdon (@RedBrogdon) [LINK] Or read it here Dart asynchronous programming: Isolates and event loops [LINK] Ref.: setState method - State class - widgets library - Dart API [LINK] markNeedsBuild method - Element class - widgets librar
Recommends Parth Dave · 2020-01 · Stack Overflow · on “Is that async function call in initState() method always be called after build() method in Flutter?”
Flutter or should I say Dart is single Threaded programming and it works in the event loop mechanism. So every time dart sees async function without await keyword it just goes and puts it in an event loop and after all current process finishes it comes back and revives that async function. If there is await keyword as you have before in print('Async function5'); it checks for event loop and revives previous stacks of events in sequence they were added with respect to delay. Check for more details [LINK] There you can find all the details of how it works. also, don't forget to check out this videos Flutter dev video [this video] and how Isolates introduced [LINK]
Recommends Suragch · 2020-02 · Stack Overflow · on “What's the difference between async and async* in Dart?”
Short answer async gives you a Future async* gives you a Stream . async You add the async keyword to a function that does some work that might take a long time. It returns the result wrapped in a Future . Future<int> doSomeLongTask() async { await Future.delayed(const Duration(seconds: 1)); return 42; } You can get that result by awaiting the Future: main() async { int result = await doSomeLongTask(); print(result); // prints '42' after waiting 1 second } async* You add the async* keyword to make a function that returns a bunch of future values one at a time. The results are wrapped in a Stream. Stream<int> countForOneMinute() async* { for (int i = 1; i <= 60; i++) { await Future.delayed(con
Recommends Suragch · 2020-04 · Stack Overflow · on “dart:io sync vs async file operations”
Let me try to summarize an answer based on the comments to my question. Correct me where I'm wrong. Running code in an async method doesn't make it run on another thread. Dart is a single threaded system. Code gets run on an event loop. Performing long running synchronous tasks will block the system whether it is in an async method or not. An isolate is a single thread. If you want to run tasks on another thread then you need to run it on another isolate. Starting another isolate is called spawning the isolate. There are a few options for running tasks on another isolate including compute [LINK] and IsolateChannel [LINK] and writing your own isolate communication code [LINK] . For File IO, t
Recommends Mäddin · 2021-04 · Stack Overflow · on “Flutter: How can I carry out resource intense background calculations without locking up the phone?”
When you start an asynchronous method, it will be computed in the same thread as the UI. That's the reason for your problem. It can be solved using Isolates. They correspond to e.g. threads in Java. For more information you can watch the video from Flutter for Isolates: [this video]
Recommends Ben Butterworth · 2021-09 · Stack Overflow · on “flutter: what's the role of FlutterEngine?”
From the javadoc [LINK] : A single Flutter execution environment. The FlutterEngine is the container through which Dart code can be run in an Android application. Dart code in a FlutterEngine can execute in the background, or it can be render to the screen by using the accompanying FlutterRenderer and Dart code using the Flutter framework on the Dart side. Rendering can be started and stopped, thus allowing a FlutterEngine to move from UI interaction to data-only processing and then back to UI interaction. You launch a dart isolate [this video] through a FlutterEngine (there is a 1 to 1 mapping). It really depends on the platform: On Android : A FlutterEngine contains a DartExecutor which runs a
Recommends Usama Karim · 2022-03 · Stack Overflow · on “What is the difference in calling Future and Future.microtask in Flutter?”
The dart team also created a video about Isolates & event loops, here is the link Isolates and Event Loops - Flutter in Focus [this video]
Cites Benjamin · 2019-12 · Stack Overflow · on “How to run clock timer in background on flutter?”
Ah, background tasks! Dart (the language Flutter uses) is single-threaded . What does single-threaded mean? Single-threaded languages such as Dart have something called an event loop. That means that Dart runs code line by line (unless you use Futures but that won't help you in this case). It registers events like button taps and waits for users to press them, etc. I recommend this article and video on single-threaded stuff: [LINK] [this video] Anyways, the way to combat this (as mentioned in the article and video above) is Isolates. When you create an Isolate in Dart, it spins up another thread to do heavy tasks or just something while the app may or may not be in focus. That way, the main threa