详解Flutter桌面应用如何进行多分辨率适配

extension SizeExtension on num {
  ///[ScreenUtil.setWidth]
  double get w => ScreenUtil().setWidth(this);
  ///[ScreenUtil.setHeight]
  double get h => ScreenUtil().setHeight(this);
  ......
)

double get screenHeight =>
    _context != null ? MediaQuery.of(_context!).size.height : _screenHeight;
double setHeight(num height) => height * scaleHeight;
// 高度的缩放比：设备的逻辑像素的高度/设计稿的高度
double get scaleHeight =>
    (_splitScreenMode ? max(screenHeight, 700) : screenHeight) /
    _uiSize.height;

extension on MediaQueryData? {
  MediaQueryData? nonEmptySizeOrNull() {
    if (this?.size.isEmpty ?? true)
      return null;
    else
      return this;
  }
}

/// The size of the media in logical pixels (e.g, the size of the screen).
///
/// Logical pixels are roughly the same visual size across devices. Physical
/// pixels are the size of the actual hardware pixels on the device. The
/// number of physical pixels per logical pixel is described by the
/// [devicePixelRatio].
final Size size;

// 文件路径：flutter_screenutil/lib/src/screenutil_init.dart
class ScreenUtilInit extends StatefulWidget {
  /// A helper widget that initializes [ScreenUtil]
  const ScreenUtilInit({
    Key? key,
    required this.builder,
    this.child,
    this.rebuildFactor = RebuildFactors.size,
    this.designSize = ScreenUtil.defaultSize,
    this.app2screenWithWidth = 1,
    this.splitScreenMode = false,
    this.minTextAdapt = false,
    this.useInheritedMediaQuery = false,
  }) : super(key: key);
  final ScreenUtilInitBuilder builder;
  final Widget? child;
  final bool splitScreenMode;
  final bool minTextAdapt;
  final bool useInheritedMediaQuery;
  final RebuildFactor rebuildFactor;
  /// The [Size] of the device in the design draft, in dp
  final Size designSize;
  /// 适用于桌面应用，应用窗口宽度与设备屏幕宽度的比例
  final double app2screenWithWidth;
  @override
  State<ScreenUtilInit> createState() => _ScreenUtilInitState();
}

dependencies:
  flutter:
    sdk: flutter
  # 获取屏幕物理参数
  screen_retriever: ^0.1.2

// 文件路径：flutter_screenutil/lib/src/screen_util.dart
/// Initializing the library.
static Future<void> init(
  BuildContext context, {
  Size designSize = defaultSize,
  double app2screenWithWidth = 1,
  bool splitScreenMode = false,
  bool minTextAdapt = false,
}) async {
  final navigatorContext = Navigator.maybeOf(context)?.context as Element?;
  final mediaQueryContext =
      navigatorContext?.getElementForInheritedWidgetOfExactType<MediaQuery>();
  final initCompleter = Completer<void>();
  WidgetsFlutterBinding.ensureInitialized().addPostFrameCallback((_) {
    mediaQueryContext?.visitChildElements((el) => _instance._context = el);
    if (_instance._context != null) initCompleter.complete();
  });
  // ** 我修改的代码 **
  Orientation orientation = Orientation.landscape;
  Size deviceSize = Size.zero;
  if (isDesktop) {
    Display primaryDisplay = await screenRetriever.getPrimaryDisplay();
    deviceSize = primaryDisplay.size;
    orientation = deviceSize.width > deviceSize.height
        ? Orientation.landscape
        : Orientation.portrait;
  } else {
    final deviceData = MediaQuery.maybeOf(context).nonEmptySizeOrNull();
    deviceSize = deviceData?.size ?? designSize;
    orientation = deviceData?.orientation ??
        (deviceSize.width > deviceSize.height
            ? Orientation.landscape
            : Orientation.portrait);
  }
  _instance
    .._context = context
    .._uiSize = designSize
    .._splitScreenMode = splitScreenMode
    .._minTextAdapt = minTextAdapt
    .._orientation = orientation
    .._screenWidth = deviceSize.width
    .._screenHeight = deviceSize.height;
  // 桌面区分设置下窗口大小
  if (isDesktop) {
    double appWidth = deviceSize.width * app2screenWithWidth;
    double appHeight = appWidth / (designSize.width / designSize.height);
    _instance._uiSize = Size(appWidth, appHeight);
  }
  _instance._elementsToRebuild?.forEach((el) => el.markNeedsBuild());
  return initCompleter.future;
}

extension SizeExtension on num {
  ///[ScreenUtil.setWidth]
  double get w => ScreenUtil().setWidth(this);
  ///[ScreenUtil.setHeight]
  double get h => ScreenUtil().setHeight(this);
  ///[ScreenUtil.radius]
  double get r => ScreenUtil().radius(this);
  ///[ScreenUtil.setSp]
  double get sp => ScreenUtil().setSp(this);
  ///smart size :  it check your value - if it is bigger than your value it will set your value
  ///for example, you have set 16.sm() , if for your screen 16.sp() is bigger than 16 , then it will set 16 not 16.sp()
  ///I think that it is good for save size balance on big sizes of screen
  double get sm => min(toDouble(), sp);
  ///屏幕宽度的倍数
  ///Multiple of screen width
  double get sw => ScreenUtil().screenWidth * this;
  ///屏幕高度的倍数
  ///Multiple of screen height
  double get sh => ScreenUtil().screenHeight * this;
  ///[ScreenUtil.setHeight]
  Widget get verticalSpace => ScreenUtil().setVerticalSpacing(this);
  ///[ScreenUtil.setVerticalSpacingFromWidth]
  Widget get verticalSpaceFromWidth =>
      ScreenUtil().setVerticalSpacingFromWidth(this);
  ///[ScreenUtil.setWidth]
  Widget get horizontalSpace => ScreenUtil().setHorizontalSpacing(this);
  ///[ScreenUtil.radius]
  Widget get horizontalSpaceRadius =>
      ScreenUtil().setHorizontalSpacingRadius(this);
  ///[ScreenUtil.radius]
  Widget get verticalSpacingRadius =>
      ScreenUtil().setVerticalSpacingRadius(this);
}