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自定义从属属性问题

binding wpf-controls wpf

serhio · 技术社区 · 15 年前

任务:

有一个UserControl-MyCircle,构建 CenterX CenterY 可绑定属性。

这是我的密码:

MyTestCircle.xaml文件

<Canvas x:Name="mainCanvas" Width="100" Height="100">
    <Ellipse x:Name="myCircle" Fill="Red" 
             Width="{Binding ElementName=mainCanvas, Path=ActualWidth}"
             Height="{Binding ElementName=mainCanvas, Path=ActualHeight}"/>     
</Canvas>

MyTestCircle.xaml.cs

public partial class MyTestCircle : UserControl
{
    public MyTestCircle()
    {
        InitializeComponent();
    }

    public double CenterX
    {
        get { return (double)GetValue(CenterXProperty); }
        set { SetValue(CenterXProperty, value); }
    }

    public static readonly DependencyProperty CenterXProperty =
        DependencyProperty.Register("CenterX", typeof(double), typeof(MyTestCircle),
        new UIPropertyMetadata(double.NaN, 
            new PropertyChangedCallback(OnCenterYChanged), 
            new CoerceValueCallback(OnCenterXCoerceValue)));

    public static void OnCenterXChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
    {
        MyTestCircle circle = (MyTestCircle)obj;
        Canvas.SetLeft(circle, (double)args.NewValue - circle.Width / 2);
    }

    public static object OnCenterXCoerceValue(DependencyObject source, object obj)
    {
        MyTestCircle circle = (MyTestCircle)obj;
        return Canvas.GetLeft(circle) + circle.Width / 2;            
    }




    public double CenterY
    {
        get { return (double)GetValue(CenterYProperty); }
        set { SetValue(CenterYProperty, value); }
    }

    public static readonly DependencyProperty CenterYProperty =
        DependencyProperty.Register("CenterY", typeof(double), typeof(MyTestCircle),
        new UIPropertyMetadata(double.NaN,
            new PropertyChangedCallback(OnCenterYChanged),
            new CoerceValueCallback(OnCenterYCoerceValue)));

    public static void OnCenterYChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
    {
        MyTestCircle circle = (MyTestCircle)obj;
        Canvas.SetTop(circle, (double)args.NewValue - circle.Height / 2);
    }

    public static object OnCenterYCoerceValue(DependencyObject source, object obj)
    {
        MyTestCircle circle = (MyTestCircle)obj;
        return Canvas.GetTop(circle) + circle.Height / 2;
    }

}

<Canvas x:Name="mainCanvas">
    <my:MyTestCircle Canvas.Left="104" Canvas.Top="132" x:Name="myTestCircle1" />
    <Line Stroke="Black"
        X1="0" Y1="0" 
        X2="{Binding ElementName=myTestCircle1, Path=CenterX}"
        Y2="{Binding ElementName=myTestCircle1, Path=CenterY}"
        />
</Canvas>

所以,测试画布中的线不跟随圆的中心。。。为什么?

编辑:

在代码或设计器中,我这个 CenterX公司 和 中心点Y坐标

2 回复 | 直到 15 年前

Kris 15 年前

您从未实际设置过CenterX和CenterY,因此它们将保持默认值,但还有其他问题。这个问题似乎是家庭作业,所以我就指出问题所在。

Coerce handlers

你需要额外的物业吗?如果你设置左上方,他们需要更新吗?如果是的话 custom Attached Properties

Mediator 15 年前

你需要这样的结果吗?

exmpale

public Circle()
    {
        InitializeComponent();


    }
    public double CenterX
    {
        get { return (double)GetValue(CenterXProperty); }
        set { SetValue(CenterXProperty, value); }
    }

    public static readonly DependencyProperty CenterXProperty =
        DependencyProperty.Register("CenterX", typeof(double), typeof(Circle),
        new UIPropertyMetadata(double.NaN,
            new PropertyChangedCallback(OnCenterXChanged),
            new CoerceValueCallback(OnCenterXCoerceValue)));


    public static void OnCenterXChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
    {
        Circle circle = (Circle)obj;
        Canvas.SetLeft(circle, (double)args.NewValue - circle.Width / 2);
    }

    public static object OnCenterXCoerceValue(DependencyObject source, object obj)
    {
        return double.Parse(obj.ToString());
    }




    public double CenterY
    {
        get { return (double)GetValue(CenterYProperty); }
        set { SetValue(CenterYProperty, value); }
    }

    public static readonly DependencyProperty CenterYProperty =
        DependencyProperty.Register("CenterY", typeof(double), typeof(Circle),
        new UIPropertyMetadata(double.NaN,
            new PropertyChangedCallback(OnCenterYChanged),
            new CoerceValueCallback(OnCenterYCoerceValue)));

    public static void OnCenterYChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
    {
        Circle circle = (Circle)obj;
        Canvas.SetTop(circle, (double)args.NewValue - circle.ActualHeight / 2);
    }

    public static object OnCenterYCoerceValue(DependencyObject source, object obj)
    {
          return double.Parse(obj.ToString());
    }

<Canvas x:Name="mainCanvas" Width="100" Height="100">
        <Ellipse x:Name="myCircle" Fill="Red" 
             Width="{Binding ElementName=mainCanvas, Path=Width}"
             Height="{Binding ElementName=mainCanvas, Path=Height}"/>
    </Canvas>

private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            myTestCircle1.CenterY = 200;
            myTestCircle1.CenterX = 300;

        }

编辑:

private void Window_KeyDown(object sender, KeyEventArgs e)
{
    if (e.Key == Key.Left)
    {

        myTestCircle1.CenterX -= 1.0;
    }
    else if (e.Key == Key.Right)
    {

        myTestCircle1.CenterX += 1.0;
    }
}

装订是工作…还是你需要别的东西?