通过媒体查询来实现 WPF 响应式设计
WPF 客户端经常需要运行在各种不同大小屏幕下，为了显示友好，所以开发的时候都需要考虑响应式设计。
布局往往通过指定比例，而不直接指定准确的大小来实现响应式布局（如 Width=”3*” ），但是具体控件的大小（如 Thickness、CornerRadius）就没有开箱即用的响应式功能了，用 viewbox 来包装，比例就跟设计稿不一样了，看起来很怪。
嗐，所以又只能自己开发了！
实现目标
- 实现类似 css @media 媒体查询类似的功能。
- 设计稿都是 1920 × 1080 实现的，在 3840 × 2160 下，应该将所有控件的大小，边框放大两倍。
- 要考虑用户在系统下设定的缩放比例。
- 同事用起来要舒服，要支持热重载。
实现逻辑
根据屏幕大小和屏幕缩放比例来计算缩放系数。
- 屏幕的 api 当然是白嫖别人写的库啦，我这里用的是 WpfScreenHelper。
public static class AppExtension
{
private static double? _factor;
/// <summary>
/// 获取当前应用的缩放系数
/// 如果 4K 屏幕，需要放大 2 倍
/// </summary>
/// <param name="app"></param>
/// <returns></returns>
public static double GetFactor(this Application app)
{
if (_factor is not null) return _factor.Value;
var screen = app.MainWindow?.GetScreen() ?? throw new ArgumentNullException(nameof(app.MainWindow));
_factor = screen.PixelBounds switch
{
{ Width: >= 3840, Height: >= 2160 } => screen.ScaleFactor / 2,
_ => screen.ScaleFactor
};
Debug.WriteLine($"屏幕大小: {screen.PixelBounds.Width} × {screen.PixelBounds.Height}");
Debug.WriteLine($"屏幕缩放: {screen.ScaleFactor * 100}%");
return _factor.Value;
}
/// <summary>
/// 根据屏幕大小和缩放系统，转换不同的数据类型
/// </summary>
/// <param name="app"></param>
/// <param name="o"></param>
/// <returns></returns>
/// <exception cref="NotSupportedException"></exception>
public static object ConvertForScreen(this Application app, object o) =>
o switch
{
double d => app.ConvertDoubleForScreen(d),
Thickness t => app.ConvertThicknessForScreen(t),
CornerRadius t => app.ConvertCornerRadiusForScreen(t),
_ => throw new NotSupportedException("不支持的转换类型")
};
public static double ConvertDoubleForScreen(this Application app, double value)
{
var factor = app.GetFactor();
return value / factor;
}
public static Thickness ConvertThicknessForScreen(this Application app, Thickness value)
{
var factor = app.GetFactor();
return new Thickness(value.Left / factor, value.Top / factor, value.Right / factor, value.Bottom / factor);
}
public static CornerRadius ConvertCornerRadiusForScreen(this Application app, CornerRadius value)
{
var factor = app.GetFactor();
return new CornerRadius(value.TopLeft / factor, value.TopRight / factor, value.BottomRight / factor,
value.BottomLeft / factor);
}
/// <summary>
/// 获取当前窗体所在的屏幕
/// </summary>
/// <param name="window">当前窗体</param>
/// <returns>窗体所在的屏幕</returns>
public static Screen GetScreen(this Window window)
{
var intPtr = new WindowInteropHelper(window).Handle; //获取当前窗口的句柄
return Screen.FromHandle(intPtr); //获取当前屏幕
}
}
自定义 xaml 标记
- 适配 Setter 上赋值和直接在控件上赋值的场景。
- 通过各种转换器来转换值。
public class ResponsiveSizeExtension : MarkupExtension
{
private static readonly Lazy<DoubleConverter> _lazyDouble = new();
private static readonly Lazy<ThicknessConverter> _lazyThickness = new();
private static readonly Lazy<CornerRadiusConverter> _lazyCornerRadius = new();
private DoubleConverter _doubleConverter => _lazyDouble.Value;
private ThicknessConverter _thickConvert => _lazyThickness.Value;
private CornerRadiusConverter _cornerRadiusConvert => _lazyCornerRadius.Value;
[ConstructorArgument("value")]
public object Value { get; set; }
public ResponsiveSizeExtension(object value)
{
if (value is string s && string.IsNullOrWhiteSpace(s)) value = "0";
Value = value;
}
public override object ProvideValue(IServiceProvider serviceProvider)
{
var target = (IProvideValueTarget)serviceProvider;
var type = target switch
{
{ TargetObject: Setter setter } => setter.Property.PropertyType,
{ TargetProperty: DependencyProperty dp } => dp.PropertyType,
_ => throw new NotSupportedException($"不是 Setter 对象或者依赖属性")
};
TypeConverter converter = type switch
{
not null when type == typeof(double) => _doubleConverter,
not null when type == typeof(Thickness) => _thickConvert,
not null when type == typeof(CornerRadius) => _cornerRadiusConvert,
_ => throw new NotSupportedException($"{type} 类型不支持")
};
var originValue = converter.ConvertFrom(Value) ?? throw new ArgumentException(nameof(Value));
var newValue = Application.Current.ConvertForScreen(originValue);
PrintLog(originValue, newValue);
return newValue;
}
private void PrintLog(object originValue, object newValue) => Debug.WriteLine($"originValue: {originValue}, newValue: {newValue}, factor: {Application.Current.GetFactor()}");
}
使用
<Window
...
xmlns:local="clr-namespace:Responsive" >
<Window.Resources>
<Style TargetType="TextBlock">
<Setter Property="FontSize" Value="{local:ResponsiveSize 19}" />
</Style>
</Window.Resources>
<Border
Margin="50"
BorderBrush="LightSeaGreen"
BorderThickness="{local:ResponsiveSize 12}">
<Grid Width="{local:ResponsiveSize 200}" Background="LightBlue">
<TextBlock Text="Test" />
</Grid>
</Border>
</Window>
效果
屏幕大小: 1920 × 1080
屏幕缩放: 100%
originValue: 12,12,12,12, newValue: 12,12,12,12, factor: 1
originValue: 200, newValue: 200, factor: 1
originValue: 16, newValue: 16, factor: 1
屏幕大小: 3840 × 2160
屏幕缩放: 100%
originValue: 12,12,12,12, newValue: 24,24,24,24, factor: 0.5
originValue: 200, newValue: 400, factor: 0.5
originValue: 16, newValue: 32, factor: 0.5
屏幕大小: 3840 × 2160
屏幕缩放: 150%
originValue: 12,12,12,12, newValue: 16,16,16,16, factor: 0.75
originValue: 200, newValue: 266.6666666666667, factor: 0.75
originValue: 16, newValue: 21.333333333333332, factor: 0.75
