自己做网站系统教程,谷德设计网景观设计,网站内容与目录结构,信息流广告加盟简介MAUI中使用Handler体系来处理不同平台的原生控件实现, 即对应的, 如果我们想要创建控件, 只需要创建基于不同平台的Handler即可。那么下面主要教大家如何通过创建Handler(事件处理程序)来构建自己的控件。开始下面, 将通过创建一个进度条控件案例, 来演示如何在MAUI项目中创… 简介MAUI中使用Handler体系来处理不同平台的原生控件实现, 即对应的, 如果我们想要创建控件, 只需要创建基于不同平台的Handler即可。那么下面主要教大家如何通过创建Handler(事件处理程序)来构建自己的控件。开始下面, 将通过创建一个进度条控件案例, 来演示如何在MAUI项目中创建平台控件并且使用它。假设控件包含基础的三项功能, 进度条颜色(Foreground)、进度条当前值(Value)、进度条模式(Indeterminate)1.第一步(声明控件类)首先, 创建MyProgressBar类, 定义对应的依赖属性internal class MyProgressBar : View{public static readonly BindableProperty ForegroundProperty BindableProperty.Create(nameof(Foreground),typeof(Color),typeof(MyProgressBar),Colors.Transparent);public static readonly BindableProperty ValueProperty BindableProperty.Create(nameof(Value),typeof(double),typeof(MyProgressBar),0.0);public static readonly BindableProperty IndeterminateProperty BindableProperty.Create(nameof(Indeterminate),typeof(bool),typeof(MyProgressBar),false);public Color Foreground{get { return (Color)GetValue(ForegroundProperty); }set { SetValue(ForegroundProperty, value); }}public double Value{get { return (double)GetValue(ValueProperty); }set { SetValue(ValueProperty, value); }}public bool Indeterminate{get { return (bool)GetValue(IndeterminateProperty); }set { SetValue(IndeterminateProperty, value); }}}2.第二步(创建标准处理程序)有了控件的标准属性定义之后, 接下来就是定义标准的Handler处理程序, 其中包含控件属性映射器及构造函数, 如下所示:partial class MyProgressBarHandler{public static PropertyMapperMyProgressBar, MyProgressBarHandler HorizontalProgressBarMapper new(ViewHandler.ViewMapper){[nameof(MyProgressBar.Value)] MapValue,[nameof(MyProgressBar.Foreground)] MapForeground, [nameof(MyProgressBar.Indeterminate)] MapIndeterminate};public MyProgressBarHandler(PropertyMapper mapper): base(mapper){}public MyProgressBarHandler() : base(HorizontalProgressBarMapper){}}3.第三步(创建平台处理程序)在属性映射器中, 我们可以很轻松看见对应了三个属性的事件处理程序, 但是目前并没有定义它, 这意味着你需要在不同平台下分别实现对应的三个事件处理程序, 所以很快阿, 赶紧在Platforms Android Controls 下定义了一个MyProgressBarHandler, 如下所示:接着继承于ViewHandler并且与原生安卓ProgressBar关联。using Android.Widget;partial class MyProgressBarHandler :ViewHandlerMyProgressBar, ProgressBar{ }重写CreateNativeView(这是创建本地控件最开始的地方)protected override ProgressBar CreateNativeView(){return new ProgressBar(Context, null, Android.Resource.Attribute.ProgressBarStyleHorizontal){Indeterminate true,Max 10000,}; }紧接着, 实现三个事件处理程序方法, MapValue、MapForeground、MapIndeterminatestatic void MapValue(MyProgressBarHandler handler, MyProgressBar view){var nativeView handler?.NativeView;nativeView.Progress (int)(view.Value * Max);}static void MapForeground(MyProgressBarHandler handler, MyProgressBar view){UpdateForeground(handler?.NativeView, view.Foreground);static void UpdateForeground(ProgressBar nativeProgressBar, Color color){if (color null){(nativeProgressBar.Indeterminate ? nativeProgressBar.IndeterminateDrawable :nativeProgressBar.ProgressDrawable)?.ClearColorFilter();}else{var tintList ColorStateList.ValueOf(color.ToNative());if (nativeProgressBar.Indeterminate)nativeProgressBar.IndeterminateTintList tintList;elsenativeProgressBar.ProgressTintList tintList;}}}static void MapIndeterminate(MyProgressBarHandler handler, MyProgressBar view){var nativeView handler?.NativeView;nativeView.Indeterminate view.Indeterminate;}4. 对应的实现iOS平台的Handler事件处理程序, 与上步骤相同, 对于事件的处理细节则对应不同平台的逻辑处理。partial class MyProgressBarHandler :ViewHandlerMyProgressBar, UIProgressView{protected override UIProgressView CreateNativeView()
{return new UIProgressView(UIProgressViewStyle.Default);}static void MapValue(MyProgressBarHandler handler, MyProgressBar view)
{var nativeView handler.NativeView;nativeView.Progress (float)view.Value;}static void MapForeground(MyProgressBarHandler handler, MyProgressBar view)
{var nativeView handler.NativeView;nativeView.ProgressTintColor view.Foreground?.ToNative();} static void MapIndeterminate(MyProgressBarHandler handler, MyProgressBar view)
{//...}}5.打开MauiProgram文件, 添加AddHandlerpublic static MauiApp CreateMauiApp(){var builder MauiApp.CreateBuilder();builder.UseMauiAppApp().ConfigureFonts(fonts {fonts.AddFont(OpenSans-Regular.ttf, OpenSansRegular);}).ConfigureMauiHandlers(handler {handler.AddHandler(typeof(MyProgressBar), typeof(MyProgressBarHandler));}); return builder.Build();}6.界面中,分别声明MAUI原生控件与自定义控件ContentPage xmlnshttp://schemas.microsoft.com/dotnet/2021/mauixmlns:xhttp://schemas.microsoft.com/winfx/2009/xamlx:ClassMAUIRender.MainPagexmlns:myclr-namespace:MAUIRender xmlns:ctorclr-namespace:MAUIRender.Controls BackgroundColor{DynamicResource SecondaryColor}GridStackLayoutProgressBar Progress30 ProgressColorRed/ctor:MyProgressBar IndeterminateTrueValue600 ForegroundGreen //StackLayout/Grid
/ContentPage运行实际效果:总结通过利用Handler来处理不同平台控件的行为, 与控件本身解耦并且更加容器支持更多的平台。
