在这种情况下，为什么 ActualWidth 和 ActualHeight 是 0.0? [英] Why are ActualWidth and ActualHeight 0.0 in this case?

问题描述

我在 Canvas 中有一个 Grid，定义如下:

I have a Grid inside a Canvas defined like this:

<Canvas x:Name="outerCanvas">
    <Grid Grid.Row="1" Name="cGrid" ShowGridLines="True" Width="{Binding Path=ActualWidth, RelativeSource={RelativeSource AncestorType={x:Type Canvas}}}" Height="{Binding Path=ActualHeight, RelativeSource={RelativeSource AncestorType={x:Type Canvas}}}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition  />
            <RowDefinition />
        </Grid.RowDefinitions>
        <Rectangle Name="rectangle1" Stroke="Black" Fill="AntiqueWhite" />
        <Rectangle Grid.Row="0" Grid.Column="1" Grid.ColumnSpan="1" Grid.RowSpan="1" Name="rectangle2" Stroke="Black" Fill="AliceBlue" />
        <Rectangle Grid.Row="0" Grid.Column="2" Grid.ColumnSpan="1" Grid.RowSpan="1" Name="rectangle3" Stroke="Black" Fill="Aqua" />
        <Rectangle Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="3" Grid.RowSpan="1" Name="rectangle4" Stroke="Black" Fill="DarkViolet" />
    </Grid>
</Canvas>

我的问题是，在 Window 构造函数中，在 InitializeComponents() 之后是 Grid.ColumnDefinitions[0].ActualWidth 或任何矩形".ActualWidth 都设置为 0.0(高度相同).我不知道该怎么做才能获得这些信息.有什么帮助吗?

My problem is that, on the Window constructor, after InitializeComponents() either Grid.ColumnDefinitions[0].ActualWidth or "any rectangle".ActualWidth are all set to 0.0 (the same for heights). I'm not figuring out what to do to get this information. Any help?

观察:

1. 我没有定义外部画布的宽度和高度，但如果我这样做了，它并不能解决我的问题.
2. 在运行时我可以看到这个Canvas/Grid占据了整个窗口空间，所以里面的每个矩形都有ActualWidths和ActualHeights
3. 网格的宽度/高度已绑定到画布，但我尝试删除此绑定，但问题仍然存在.

1. I'm not defining the outer canvas width and height but if I do, it doesn't solve my problem.
2. At runtime I can see that this Canvas/Grid occupies the entire window space, so every rectangle inside it has ActualWidths and ActualHeights
3. The grid's width/height is bound to the canvas but I tried removing this binding and my problem still persists.

推荐答案

ActualHeight 和 ActualWidth 直到控件被测量和排列.通常 InitializeComponent() 中没有任何东西会导致测量，所以当它返回时，这些仍然是零.

ActualHeight and ActualWidth are not set until the control is measured and arranged. Usually there is nothing in InitializeComponent() that causes a measure, so when it returns these will still be zero.

您可以通过在窗口的 InitializeComponent() 之后手动调用窗口的 Measure() 和 Arrange() 方法来强制提前计算这些值代码>返回.

You can force these to be computed earlier by simply calling the window's Measure() and Arrange() methods manually after the window's InitializeComponent() returns.

如果您根据内容调整大小:

If you are sizing to content:

window.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
window.Arrange(new Rect(0, 0, window.DesiredSize.Width, window.DesiredSize.Height));

如果您使用的是明确的窗口大小:

If you are using an explicit window size:

window.Measure(new Size(Width, Height));
window.Arrange(new Rect(0, 0, window.DesiredSize.Width, window.DesiredSize.Height));

这篇关于在这种情况下，为什么 ActualWidth 和 ActualHeight 是 0.0?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！