.net - 如何在窗口显示前计算 ActualWidth ActualHeight

Question

我正在尝试在窗口显示之前计算 StackPanel width, height(位于网格的中间单元格)(例如窗口构造函数)。如何实现？

<Window x:Class="WpfApplication2.TestWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="TestWindow" Height="300" Width="300">
<Grid Name="grid">
    <Grid.ColumnDefinitions>
        <ColumnDefinition></ColumnDefinition>
        <ColumnDefinition></ColumnDefinition>
        <ColumnDefinition></ColumnDefinition>
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition></RowDefinition>
        <RowDefinition></RowDefinition>
        <RowDefinition></RowDefinition>
    </Grid.RowDefinitions>

    <StackPanel Grid.Row="1" Grid.Column="1" Name="stackPanel"></StackPanel>

</Grid>

Window 的测量也和 stackPanel 一样将 DesiredSize 设置为 {0;0}

public partial class TestWindow : Window
{
    public TestWindow()
    {
        InitializeComponent();

        this.Measure(new Size(this.Width, this.Height)); // -> this.DesiredSize = {0;0}

        ...

    }
}

编辑1

以下适用于 FixedPage:

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

然后我们可以访问 stackPanel.ActualWidth 和 stackpanel.ActualHeight。

但是对于Window，它不起作用。

Answer 1

尝试 Loaded 事件:

public TestWindow()
{
    InitializeComponent();
    this.Loaded += new RoutedEventHandler(TestWindow_Loaded);
}

void TestWindow_Loaded(object sender, RoutedEventArgs e)
{
    //this.DesiredSize shouldnt be {0,0} now
}

编辑: 由于 StackPanel 已经占据了最大的 Size，即使其中没​​有项目，它的 SizeChanged 事件只会在您添加很多项时触发，因此您可以像这样使用 StackPanel 的 SizeChanged 事件:

private void spTest_SizeChanged(object sender, SizeChangedEventArgs e)
{
    if (!(e.PreviousSize.Height == 0 && e.PreviousSize.Width == 0)) //will also be fired after loading
    {
        //Create another Page
    }
}

EDIT2:另一种可能的解决方案:

public MainWindow()
{
    InitializeComponent();
    yourStackPanelName.Loaded += new RoutedEventHandler(yourStackPanelName_Loaded);
}

void yourStackPanelName_Loaded(object sender, RoutedEventArgs e)
{
    double height = ((StackPanel)sender).ActualHeight;
    double width = ((StackPanel)sender).ActualWidth;
}