以前,我直接设置了UserControl的模板,而不是通过样式设置,并且一切运行良好:可以使用this.Template.LoadContent()或通过this.Template.FindName(“ MyControlName”访问内容的根“,this),两个调用都在base.OnApplyTemplate()调用之后在OnApplyTemplate中完成。现在,我需要一种样式,因为我使用两个DataTriggers来显示一种Control类型或一种在Binding值函数中的其他类型。
通过下面的XAML调试,我看到在base.OnApplyTemplate调用this.Template.LoadContent()之后,返回一个Border,其Child设置为空的ContentPresenter。我希望获得wpf:TimeSpanPicker元素。
我已阅读this的答案,由于上述调试的结果,它对我没有帮助。与this answer相同。
之前,我的UserControl将此内容直接存在于其XAML文件中:
<UserControl.Template>
<ControlTemplate>
<wpf:TimeSpanPicker
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
HorizontalContentAlignment="Stretch"
VerticalContentAlignment="Stretch"
Name="MyTimeSpanPicker"
Margin="0,0,7,0"/>
</ControlTemplate>
</UserControl.Template>
现在我有了这个
<UserControl.Style>
<Style TargetType="UserControl">
<Style.Triggers>
<DataTrigger Binding="{Binding Mode=OneWay, Converter={StaticResource ClockToType}}"
Value="TimerData">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="UserControl">
<wpf:TimeSpanPicker
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
HorizontalContentAlignment="Stretch"
VerticalContentAlignment="Stretch"
Name="MyTimeSpanPicker"
Margin="0,0,7,0"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</DataTrigger>
<DataTrigger Binding="{Binding Mode=OneWay, Converter={StaticResource ClockToType}}"
Value="AlarmData">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="UserControl">
<Button>Not yet implemented</Button>
</ControlTemplate>
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</UserControl.Style>
隐藏的代码包括:
internal wpf_timespanpicker.TimeSpanPicker GetMyTimeSpanPicker()
{
return (wpf_timespanpicker.TimeSpanPicker)Template.LoadContent();
}
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
GetMyTimeSpanPicker().TimeSpanValueChanged += MyTimeSpanPicker_TimeSpanValueChanged;
}
private void MyTimeSpanPicker_TimeSpanValueChanged(object sender, EventArgs e)
{
CurrentValue = GetMyTimeSpanPicker().TimeSpan;
}
ClockToType值转换器仅将我的Clock类的实例之一转换为其类型名称。
现在由于答案而部分起作用,但是当UserControl的CurrentValue依赖项属性更改时,我需要设置TimeSpanPicker的TimeSpan依赖项属性,而当时间跨度选择器尚未使用时,可以更改CurrentValue依赖项属性已加载。推迟此设置的最佳方法是什么?在设置之前放置ApplyTemplate调用似乎无效,因为我在其中保留对TimeSpanPicker的引用的类变量为null:
private static void OnCurrentValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var o = d as ClockValueScreen;
o.ApplyTemplate();
o.MyTimeSpanPicker.TimeSpan = (TimeSpan)e.NewValue; // but here o.MyTimeSpanPicker is null
}
public override void OnApplyTemplate()
{
base.OnApplyTemplate(); // execution reaches this point from the ApplyTemplate call above
}
private void MyTimeSpanPicker_Loaded(object sender, RoutedEventArgs e)
{
MyTimeSpanPicker = (wpf_timespanpicker.TimeSpanPicker)sender;
MyTimeSpanPicker.TimeSpanValueChanged += MyTimeSpanPicker_TimeSpanValueChanged;
}
答案 0 :(得分:1)
您无法使用OnApplyTemplate()
,因为在绑定已解决并且转换器返回值“ TimerData”之前,没有TimeSpanPicker
元素可用。
相反,您可以做的是在XAML中挂接事件处理程序:
<ControlTemplate TargetType="UserControl">
<wpf:TimeSpanPicker
Loaded="OnLoaded"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
HorizontalContentAlignment="Stretch"
VerticalContentAlignment="Stretch"
Name="MyTimeSpanPicker"
Margin="0,0,7,0"/>
</ControlTemplate>
...然后在后台代码中处理它;
private void OnLoaded(object sender, RoutedEventArgs e)
{
wpf_timespanpicker.TimeSpanPicker timeSpanPicker = ( wpf_timespanpicker.TimeSpanPicker)sender;
}
编辑:如果您想在TimeSpanPicker
属性更改时对CurrentValue
进行操作,则可以使用VisualTreeHelper
类在视觉树:
private static void OnCurrentValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var o = (ClockValueScreen)d;
var timeSpanPicker = FindVisualChild<wpf_timespanpicker.TimeSpanPicker>(o);
//...
}
private static T FindVisualChild<T>(Visual visual) where T : Visual
{
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(visual); i++)
{
Visual child = (Visual)VisualTreeHelper.GetChild(visual, i);
if (child != null)
{
T correctlyTyped = child as T;
if (correctlyTyped != null)
{
return correctlyTyped;
}
T descendent = FindVisualChild<T>(child);
if (descendent != null)
{
return descendent;
}
}
}
return null;