What is the difference between didChangeDependencies and initState?

Question

I am new to flutter and when I want to call my context in InitState it throws an error : which is about BuildContext.inheritFromWidgetOfExactType but then I use did

Answer 1

This is a supplemental answer showing what the OP described.

The State class of a StatefulWidget has a context property. This build context is first available in didChangeDependencies. Trying to use context in initState will cause an error.

class HomeWidget extends StatefulWidget {
  const HomeWidget({Key key}) : super(key: key);

  @override
  _HomeWidgetState createState() => _HomeWidgetState();
}

class _HomeWidgetState extends State<HomeWidget> {
  @override
  void initState() {
    print('initState');
    // print(Theme.of(context));        // ERROR!
    super.initState();
  }

  @override
  void didChangeDependencies() {
    print('didChangeDependencies');
    print(Theme.of(context));           // OK
    super.didChangeDependencies();
  }

  @override
  Widget build(BuildContext context) {
    print('build');
    print(Theme.of(context));           // OK
    return Container();
  }
}

Running that gives the print statements in the following order:

initState
didChangeDependencies
ThemeData#93b06
build
ThemeData#93b06

See also Working with didChangeDependencies() in Flutter

Answer 2

The answer is here

This method should not be called from widget constructors or from State.initState methods, because those methods would not get called again if the inherited value were to change. To ensure that the widget correctly updates itself when the inherited value changes, only call this (directly or indirectly) from build methods, layout and paint callbacks, or from State.didChangeDependencies.