Question

我正在尝试创建一个移动矩形（rect）。这是相关的代码：

let timer = new Threading.DispatcherTimer();
timer.Tick.Add(fun _ -> Canvas.SetLeft(rect, Canvas.GetLeft(rect)+0.01) |> ignore)
timer.Start()

问题在于，如果我将鼠标移动到窗口上，动画就会变慢。如果我设置计时器间隔：

timer.Interval <- TimeSpan.FromMilliSeconds(30.0)

然后动画根本不工作。我做错了什么？谢谢。

Answer 1

我有两个建议：

如果您正在使用f＃交互式，请检查您是否已安装WFP事件循环。F＃交互式默认设置了一个WinForms事件循环，WinForms和WFP事件循环之间存在一些兼容性，但不是所有东西都可以正常工作。要安装事件循环，请使用以下脚本：

#light

// When running inside fsi, this will install a WPF event loop
#if INTERACTIVE

#I "c:/Program Files/Reference Assemblies/Microsoft/Framework/v3.0";;
#I "C:/WINDOWS/Microsoft.NET/Framework/v3.0/WPF/";;
#r "presentationcore.dll";;
#r "presentationframework.dll";;
#r "WindowsBase.dll";;

module WPFEventLoop = 
    open System
    open System.Windows
    open System.Windows.Threading
    open Microsoft.FSharp.Compiler.Interactive
    open Microsoft.FSharp.Compiler.Interactive.Settings
    type RunDelegate< b> = delegate of unit ->  b 

    let Create() = 
        let app  = 
            try 
                // Ensure the current application exists. This may fail, if it already does.
                let app = new Application() in 
                // Create a dummy window to act as the main window for the application.
                // Because we re in FSI we never want to clean this up.
                new Window() |> ignore; 
                app 
             with :? InvalidOperationException -> Application.Current
        let disp = app.Dispatcher
        let restart = ref false
        { new IEventLoop with
             member x.Run() =   
                 app.Run() |> ignore
                 !restart
             member x.Invoke(f) = 
                 try disp.Invoke(DispatcherPriority.Send,new RunDelegate<_>(fun () -> box(f ()))) |> unbox
                 with e -> eprintf "

 ERROR: %O
" e; rethrow()
             member x.ScheduleRestart() =   ()
                 //restart := true;
                 //app.Shutdown()
        } 
    let Install() = fsi.EventLoop <-  Create()

WPFEventLoop.Install();;

#endif

我没有进行过太多测试，但我认为使用动画故事板会比使用计时器得到更加平滑和一致的结果。我认为这会像这样（改变宽度属性，我还没想出如何改变位置）：

#light

open System
open System.Windows
open System.Windows.Controls
open System.Windows.Shapes
open System.Windows.Media
open System.Windows.Media.Animation


let rect = new Rectangle(Fill = new SolidColorBrush(Colors.Red), Height = 20., Width = 20., Name = "myRectangle")

let canvas = 
    let c = new Canvas()
    c.Children.Add(rect) |> ignore
    c

NameScope.SetNameScope(canvas, new NameScope());
canvas.RegisterName(rect.Name, rect)

let window = new Window(Content = canvas)

let nfloat f = new Nullable<float>(f)

let myDoubleAnimation = new DoubleAnimation(From = nfloat 20.0, To = nfloat 50.0,
                                            Duration = new Duration(TimeSpan.FromSeconds(5.)),
                                            RepeatBehavior = RepeatBehavior.Forever)
let myStoryboard = 
    let sb = new Storyboard()
    sb.Children.Add(myDoubleAnimation)
    sb

Storyboard.SetTargetName(myDoubleAnimation, rect.Name);
Storyboard.SetTargetProperty(myDoubleAnimation, new PropertyPath(Rectangle.WidthProperty))

rect.Loaded.Add(fun _ -> myStoryboard.Begin canvas)

let main() =
    let app = new Application()
    app.Run window |> ignore

[<STAThread>]
do main()

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