Question

我在C＃-WPF工作。

我制作了自己的UserControl，这是一个简单的交叉。使用坐标，我可以在图像上绘制X.

参数是：

CenterPoint：十字架中心
前景：十字架的颜色
厚度：十字架的厚度

我的Cross.xaml：

<UserControl x:Name="userControl"
             x:Class="Project.Cross">
    <Grid>
        <Line Stroke="{Binding Foreground, ElementName=userControl}"
              StrokeThickness="{Binding Thickness, ElementName=userControl}"
              X1="{Binding X1, ElementName=userControl, Mode=OneWay}"
              X2="{Binding X2, ElementName=userControl, Mode=OneWay}"
              Y1="{Binding Y1, ElementName=userControl, Mode=OneWay}"
              Y2="{Binding Y2, ElementName=userControl, Mode=OneWay}" />

        <Line Stroke="{Binding Foreground, ElementName=userControl}"
              StrokeThickness="{Binding Thickness, ElementName=userControl}"
              X1="{Binding X2, ElementName=userControl, Mode=OneWay}"
              X2="{Binding X1, ElementName=userControl, Mode=OneWay}"
              Y1="{Binding Y1, ElementName=userControl, Mode=OneWay}"
              Y2="{Binding Y2, ElementName=userControl, Mode=OneWay}"/>
    </Grid>
</UserControl>

我的Cross.xaml.cs：

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

    public readonly static DependencyProperty CenterPointProperty = DependencyProperty.Register("CenterPoint",
        typeof(PointF), typeof(Cross),
        new PropertyMetadata(default(PointF)));

    public PointF CenterPoint
    {
        get { return (PointF)GetValue(CenterPointProperty); }
        set { SetValue(CenterPointProperty, value); }
    }

    public readonly static DependencyProperty ThicknessProperty = DependencyProperty.Register("Thickness",
        typeof(int), typeof(Cross),
        new PropertyMetadata(2));

    public int Thickness
    {
        get { return (int)GetValue(ThicknessProperty); }
        set { SetValue(ThicknessProperty, value); }
    } 

    public float X1
    {
        get
        {
            return (float)(CenterPoint.X - (Width / 2));
        }
    }
    public float X2
    {
        get
        {
            return (float)(CenterPoint.X + (Width / 2));
        }
    }
    public float Y1
    {
        get
        {
            return (float)(CenterPoint.Y - (Height / 2));
        }
    }
    public float Y2
    {
        get
        {
            return (float)(CenterPoint.Y + (Height / 2));
        }
    }
}

我可以这样称呼：

<local:Cross CenterPoint="{Binding Point}" Thickness="8" Foreground="Yellow" Height="40" Width="40"/>

我遇到问题，不显示十字架。我添加了断点，当我更改CenterPoint时，似乎值X1，X2，...不会刷新。如何强制C＃重新评估这些值？（希望这能解决我的问题）

谢谢

Answer 1

如果希望在将CenterPoint依赖项属性设置为新值时刷新X1，X2，Y1和Y2只读属性，则UserControl应实现INotifyPropertyChanged接口。然后，您可以为依赖项属性注册PropertyChangedCallback，并为只读属性引发PropertyChanged事件：

public partial class Cross : UserControl, INotifyPropertyChanged
{
    public Cross()
    {
        InitializeComponent();
    }

    public readonly static DependencyProperty CenterPointProperty = DependencyProperty.Register("CenterPoint",
        typeof(PointF), typeof(Cross),
        new PropertyMetadata(default(PointF), new PropertyChangedCallback(OnCenterPointUpdated))));

    private static void OnCenterPointUpdated(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        Cross cross = d as Cross;
        cross.NotifyPropertyChanged("X1");
        cross.NotifyPropertyChanged("X2");
        cross.NotifyPropertyChanged("Y1");
        cross.NotifyPropertyChanged("Y2");
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }

    ...
}

Answer 2

mm8的方法可用于更新X1等，但还需要解决其他问题才能使控制工作。

我正在使用另一种方法来更新坐标属性：将X1等转换为read-only dependency properties，让用户控件在CenterPoint更改时以及控件的大小更改时更新它们。

我还将您的winforms PointF更改为WPF System.Windows.Point，double使用X和Y，我已更改{ {1}}到Thickness，因为WPF使用float来表示线条粗细，您也可以充分利用它。

我正在更新float事件的坐标，这是至关重要的，因为否则，只有当实际大小为0 x 0时才会在控件创建时设置坐标属性，SizeChanged Width是Height。

最后，您应该使用NaN和ActualWidth，这些更新为“实时”，而不是ActualHeight和Height，它们是设计时属性值。如果您给它一个固定的Width和Width，效果将是相同的;使用Height和ActualWidth允许它伸展以适合容器（如果需要）。

ActualHeight

最后，您不需要明确地设置绑定public partial class Cross : UserControl { public Cross() { InitializeComponent(); SizeChanged += Cross_SizeChanged; } private void Cross_SizeChanged(object sender, SizeChangedEventArgs e) { UpdateXYProperties(); } protected void UpdateXYProperties() { X1 = (float)(CenterPoint.X - (ActualWidth / 2)); X2 = (float)(CenterPoint.X + (ActualWidth / 2)); Y1 = (float)(CenterPoint.Y - (ActualHeight / 2)); Y2 = (float)(CenterPoint.Y + (ActualHeight / 2)); } public readonly static DependencyProperty CenterPointProperty = DependencyProperty.Register(nameof(CenterPoint), typeof(Point), typeof(Cross), new PropertyMetadata(default(Point), CenterPoint_PropertyChanged)); private static void CenterPoint_PropertyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e) { ((Cross)obj).UpdateXYProperties(); } public Point CenterPoint { get { return (Point)GetValue(CenterPointProperty); } set { SetValue(CenterPointProperty, value); } } public readonly static DependencyProperty ThicknessProperty = DependencyProperty.Register(nameof(Thickness), typeof(float), typeof(Cross), new PropertyMetadata(2.0F)); public float Thickness { get { return (float)GetValue(ThicknessProperty); } set { SetValue(ThicknessProperty, value); } } #region Read-Only Properties #region X1 Property public float X1 { get { return (float)GetValue(X1Property); } protected set { SetValue(X1PropertyKey, value); } } internal static readonly DependencyPropertyKey X1PropertyKey = DependencyProperty.RegisterReadOnly("X1", typeof(float), typeof(Cross), new PropertyMetadata(0.0F)); public static readonly DependencyProperty X1Property = X1PropertyKey.DependencyProperty; #endregion X1 Property #region X2 Property public float X2 { get { return (float)GetValue(X2Property); } protected set { SetValue(X2PropertyKey, value); } } internal static readonly DependencyPropertyKey X2PropertyKey = DependencyProperty.RegisterReadOnly("X2", typeof(float), typeof(Cross), new PropertyMetadata(0.0F)); public static readonly DependencyProperty X2Property = X2PropertyKey.DependencyProperty; #endregion X2 Property #region Y1 Property public float Y1 { get { return (float)GetValue(Y1Property); } protected set { SetValue(Y1PropertyKey, value); } } internal static readonly DependencyPropertyKey Y1PropertyKey = DependencyProperty.RegisterReadOnly("Y1", typeof(float), typeof(Cross), new PropertyMetadata(0.0F)); public static readonly DependencyProperty Y1Property = Y1PropertyKey.DependencyProperty; #endregion Y1 Property #region Y2 Property public float Y2 { get { return (float)GetValue(Y2Property); } protected set { SetValue(Y2PropertyKey, value); } } internal static readonly DependencyPropertyKey Y2PropertyKey = DependencyProperty.RegisterReadOnly("Y2", typeof(float), typeof(Cross), new PropertyMetadata(0.0F)); public static readonly DependencyProperty Y2Property = Y2PropertyKey.DependencyProperty; #endregion Y2 Property #endregion Read-Only Properties }，因为Mode=OneWay等无法更新绑定源（在这种情况下，这是您自己的Line.X1等），所以默认情况下它们已经X1。

OneWay

最后，几乎可以肯定：<Grid> <Line Stroke="{Binding Foreground, ElementName=userControl}" StrokeThickness="{Binding Thickness, ElementName=userControl}" X1="{Binding X1, ElementName=userControl}" X2="{Binding X2, ElementName=userControl}" Y1="{Binding Y1, ElementName=userControl}" Y2="{Binding Y2, ElementName=userControl}" /> <Line Stroke="{Binding Foreground, ElementName=userControl}" StrokeThickness="{Binding Thickness, ElementName=userControl}" X1="{Binding X2, ElementName=userControl}" X2="{Binding X1, ElementName=userControl}" Y1="{Binding Y1, ElementName=userControl}" Y2="{Binding Y2, ElementName=userControl}" /> </Grid>设计的效果是，如果它不是控件的实际中心，则偏移控件边界外的交叉。如果这是你的意图，不要费心阅读本段的其余部分。如果这不是您的意图，您可以按如下方式重写CenterPoint并丢失UpdateXYProperties()属性：

CenterPoint

但这取决于你和圣安德鲁。

在UserControl中重新评估属性

2 个答案: