绑定到画布 [英] Binding to Canvas

问题描述

我的课堂上有一个canvas属性，我想知道是否可以将它绑定到xaml中的画布上吗？

I have a canvas property in my class and I was wondering if it's possible to bind that to a canvas in xaml?

数据绑定如何在画布中工作？

How would the databinding work in the canvas?

<Canvas ItemSource="{Binding ClassCanvas}" />

推荐答案

如果您希望XAML中定义的Canvas包含您可以在班级中将整个Canvas作为单个项目编写：

If you want your Canvas defined in XAML to include the entire Canvas in your class as a single item you can write:

<Canvas>
  <ContentPresenter Content="{Binding ClassCanvas}" />
  ... other items here ...
</Canvas>

如果您希望XAML中定义的Canvas包含与类中定义的Canvas相同的UIElements ，这是不可能的，因为一个UIElement只能有一个UIElement父对象。因此，如果类中定义的Canvas是给定UIElement的父级，则XAML中定义的Canvas不能为父。

If you want your Canvas defined in XAML to include all the same UIElements as the Canvas defined in your class, it is impossible because a UIElement can have only one UIElement parent. So if the Canvas defined in the class is the parent of a given UIElement, the Canvas defined in XAML can't be.

如果希望Canvas显示来自以下位置的数据您可以在类中定义Canvas中的每个UIElement时，都可以使用带有Canvas面板和DataTemplate的ItemsControl：

If you want your Canvas to display data from each UIElement in the Canvas defined in your class, you can do this with an ItemsControl with a Canvas panel and a DataTemplate:

<ItemsControl ItemsSource="{Binding ClassCanvas.Children}">
  <ItemsControl.ItemsPanel>
    <ItemsPanelTemplate>
      <Canvas />
    </ItemsPanelTemplate>
  </ItemsControl>
  <ItemsControl.ItemsContainerStyle>
    <Style>
      <Setter Property="Canvas.Left" Value="{Binding (Canvas.Left)}" />
      <Setter Property="Canvas.Left" Value="{Binding (Canvas.Top)}" />
      <Setter Property="Template">
        <Setter.Value>
          <ControlTemplate>
            ... display of UIElement here, either using VisualBrush or custom display
          </ControlTemplate>
        <Setter.Value>
      </Setter>
    </Style>
  </ItemsControl.ItemsContainerStyle>
</ItemsControl>

请注意，由于此代码不是INotifyCollectionChanged集合，因此只会扫描Children属性一次。

Note that this code will only scan the Children property once since it is not an INotifyCollectionChanged collection.

如果您要绑定到包含UIElements集合且其Canvas.Top和Canvas.Left属性设置为类的属性，则如果容器是一个ObservableCollection而不是Canvas。

If you want to bind to a property in your class that contains a collection of UIElements with their Canvas.Top and Canvas.Left properties set, you can easily do this if the container is an ObservableCollection instead of a Canvas.

Canvas类从未设计用于数据层。我强烈建议您在该处切换到使用ObservableCollection，而仅将Canvas用作视图的一部分。

The Canvas class was never designed for use within your data layer. I would strongly recommend you switch to using an ObservableCollection there and only use Canvas as part of your view.

这篇关于绑定到画布的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！