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在xaml中设置时,WPF附加的属性不在后面触发代码

attached-properties dependencies wpf

4

Sheridan · 技术社区 · 14 年前

我有一个自定义的ClockFace用户控件,它具有允许更改颜色、字体和指针(作为路径对象)的属性。这在自定义时间选择器和时钟用户控件中使用。在这些父控件中,可以在xaml中的ClockFace对象上设置ClockFace属性。我要做的是公开这些时钟面属性,以便可以在这两个父控件(例如时钟和计时器选择器对象)上设置它们。我认为让它们附加属性可以做到这一点,所以我尝试了其中一种颜色属性。

public static readonly DependencyProperty HourTicksBrushProperty = DependencyProperty.RegisterAttached("HourTicksBrush", typeof(Brush), typeof(ClockFace), new FrameworkPropertyMetadata(Brushes.Black, FrameworkPropertyMetadataOptions.AffectsRender));
public static void SetHourTicksBrush(DependencyObject element, Brush value)
{
    element.SetValue(HourTicksBrushProperty, value);
}
public static Brush GetHourTicksBrush(DependencyObject element)
{
    return (Brush)element.GetValue(HourTicksBrushProperty);
}

<Controls:Clock Controls:ClockFace.HourTicksBrush="Aqua" />

它编译得很好,但是尽管所附HourTicksBrushProperty的默认值(Brushes.Black)显示,父时钟控件(Aqua)上设置的值从不触发上述方法或更改颜色。我遗漏了什么吗?

为了清楚起见,我希望能够在父控件上使用上面的xaml来设置子时钟面控件的HourTicksBrush属性。

2 回复 | 直到 14 年前

1

6

Rob Fonseca-Ensor 14 年前

附加属性类中的“get”和“set”方法实际上只是用于您自己的代码隐藏的方便方法。XAML解析器忽略这些,调用element.SetValue本身。如果要响应setter,则必须为 FrameworkPropertyMetadata

public static readonly DependencyProperty HourTicksBrushProperty = DependencyProperty.RegisterAttached(
    "HourTicksBrush", 
    typeof(Brush), 
    typeof(ClockFace), 
    new FrameworkPropertyMetadata(
        Brushes.Black, 
        FrameworkPropertyMetadataOptions.AffectsRender,
        HourTicksBrushChanged));

public static void SetHourTicksBrush(DependencyObject element, Brush value)
{
    element.SetValue(HourTicksBrushProperty, value); //not always called
}
public static Brush GetHourTicksBrush(DependencyObject element)
{
    return (Brush)element.GetValue(HourTicksBrushProperty); //not always called
}
private static void HourTicksBrushChanged(DependencyObject sender, somethingsomethingArgs args){
    // do stuff with sender and args.NewValue here
}

2

0

Maarten Van Genechten 14 年前

使用类似于:

public static readonly DependencyProperty HourTicksBrushProperty = DependencyProperty.RegisterAttached("HourTicksBrush", typeof(Brush), typeof(ClockFace), new FrameworkPropertyMetadata(Brushes.Black, FrameworkPropertyMetadataOptions.AffectsRender));


public static Brush HourTicksBrush
{
    get { return (Brush)GetValue(HourTicksBrushProperty); }
    set { SetValue(HourTicksBrushProperty); }
}

<Controls:Clockface.HourTicks Fill="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=HourTicksBrush}/>

我不确定是否在相对资源中使用TemplatedParent或Self