有没有办法在initstate flutter中访问屏幕高度和宽度？

Question

我正在尝试预加载我的图像并在 initstate 中声明一次

示例：

late List<String> _assetBg;
  late List<Image> _imagesBg;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    _assetBg = ['assets/images/1.jpg',
      'assets/images/2.jpg',
      'assets/images/3.jpg',
      'assets/images/4.jpg'];

    _imagesBg = _initializeListImage(context, _assetBg);
          
    WidgetsBinding.instance!.addPostFrameCallback((timeStamp) {
      _tombolRenderBox =
          _tombolKey.currentContext!.findRenderObject() as RenderBox;
    });
  }

问题是：

List<Image> _initializeListImage (BuildContext context,List<String> assets){
    List<Image> result = [];
    for (var asset in assets) {
      result.add(
          Image(
            image: AssetImage(asset),
            ///Problem is here :
            height: MediaQuery.of(context).size.height,
            width: MediaQuery.of(context).size.width * 2,
            fit: BoxFit.cover,

          )
      );
    }
    return result;
  }

并在此处预重新加载：

@override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _prechaceImage(context, _imagesBg);
  }

void _prechaceImage(BuildContext context, List<Image> images){
    for(var image in images){
      precacheImage(image.image, context);
    }
  }

但这给了我一个错误

错误：

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

有办法解决这个问题吗？我真的需要计算屏幕宽度来动画我的小部件的旋转，感谢您的帮助。

Answer 1

您可以使用

window

包中的

dart:ui

：

import 'dart:ui';

// Screen size in density independent pixels
var screenWidth = (window.physicalSize.shortestSide / window.devicePixelRatio);
var screenHeight = (window.physicalSize.longestSide / window.devicePixelRatio);

// Screen size in real pixels
var screenWidthPixels = window.physicalSize.shortestSide;
var screenHeightPixels = window.physicalSize.longestSide;

参考：https://api.flutter.dev/flutter/dart-ui/window.html

Answer 2

window.physicalSize

已弃用，并将在未来版本中删除。

您可以使用

PlatformDispatcher

  final view = PlatformDispatcher.instance.views.first;
  print(view.physicalSize);

Answer 3

普通班可以省钱

class ScreenSize {
   static double width;
   static double height;
}

并在启动屏幕或main.dart的构建方法中

ScreenSize.width = Mediaquery.of(context).size.width;
ScreenSize.height= Mediaquery.of(context).size.height;

您可以在应用程序的任何屏幕上使用它，我希望这会有所帮助