setState() doesn't execute until the enclosing function returns

Question

So I was trying this code in flutter:

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyA         


        

Answer 1

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

    • by flutter team member Andrew Brogdon (@RedBrogdon)

• Or read it here

  • Dart asynchronous programming: Isolates and event loops

Ref.:

1. setState method - State class - widgets library - Dart API

2. markNeedsBuild method - Element class - widgets library - Dart API

3. scheduleBuildFor method - BuildOwner class - widgets library - Dart API

4. drawFrame method - WidgetsBinding class - widgets library - Dart API

5. handleDrawFrame method - SchedulerBinding class - scheduler library - Dart API

6. buildScope method - BuildOwner class - widgets library - Dart API

7. dart engine loop - Google Search

8. Dart Programming - Loops - Tutorialspoint

9. optimization - What is the optimal render loop in Dart 2? - Stack Overflow

10. Understanding Flutter Render Engine - Stack Overflow

11. Technical overview - Flutter

12. Flutter - Dart API docs

13. flutter/spinning_square.dart at master · flutter/flutter

14 .dart engine - Google Search

15. scheduler library - Dart API

16. flutter/binding.dart at master · flutter/flutter

17. scheduler library - Dart API

18. frame scheduling flutter - Google Search

19. scheduleFrame method - SchedulerBinding class - scheduler library - Dart API

20. scheduler library - Dart API

21. packages/flutter/lib/scheduler.dart - external/github.com/flutter/flutter - Git at Google

22. flutter/spinning_square.dart at master · flutter/flutter

23. dart engine - Google Search

24. threading | Dart Package

25. isolate flutter - Google Search