Question 219677 in Flutter Question posted in
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flutter initState with MediaQuery.of(context)

I would like to initialize some of the widgets with the size and width of the screen.

When I try to use the initState method like

double anyvariable = 30.0;
@override
void initState() {
    super.initState();
    var windowwidth     = MediaQuery.of(context).size.width;
    setState(() {
      anyvariable       = _mediaQueryData.size.width/2;
    });
 }

I receive the error

dependOnInheritedWidgetOfExactType<MediaQuery>() or dependOnInheritedElement() was called before
_CustomWidgetState.initState() completed. ...

How do I fix this error or how to I init the widgets with information about the width and height of the screen available before build?

Tags:

2

Answers


  1. 0

    you can initialize you sizes on your build function instead of initState

    like this code

      double windowwidth = 0;
  double anyvariable = 0;
  @override
  Widget build(BuildContext context) {
    windowwidth = MediaQuery.of(context).size.width;
    double anyvariable = _mediaQueryData.size.width/2;
    return const Placeholder();
  }
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  2. 0

    You are calling setState inside initState, with is not a good practice and can also give you the error you’re facing.

    To solve this, you can write this way.

    1. You can wrap the code with WidgetsBinding.instance.addPostFrameCallback:

    double anyvariable = 30.0;

@override
void initState() {
    super.initState();

    WidgetsBinding.instance.addPostFrameCallback((timeStamp) {

       var windowwidth = MediaQuery.of(context).size.width;

       setState(() {
           anyvariable = _mediaQueryData.size.width/2;
        });

     });

 }
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