如何：设置元素的宽度属性 - WPF

2025-12-08 06:46:04 | 觉醒指南

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示例：

此示例直观地显示了 Windows Presentation Foundation （WPF） 中四个与宽度相关的属性之间的呈现行为差异。

FrameworkElement 类公开四个描述元素宽度特征的属性。 这四个属性可能会发生冲突，当它们发生冲突时，优先值将按如下方式确定：MinWidth 值优先于 MaxWidth 值，而值又优先于 Width 值。 第四个属性 ActualWidth是只读的，它报告通过与布局过程的交互所确定的实际宽度。

以下可扩展应用程序标记语言（XAML）示例将 Rectangle 元素（rect1）绘制为 Canvas子级。 可以使用表示 Rectangle、ListBox和 MinWidth属性值的一系列 MaxWidth 元素来更改 Width 的宽度属性。 通过这种方式，每个属性的优先级会以可视化形式显示。

Set the Rectangle Width:

25

50

75

100

125

150

175

200

225

250

Set the Rectangle MinWidth:

25

50

75

100

125

150

175

200

225

250

Set the Rectangle MaxWidth:

25

50

75

100

125

150

175

200

225

250

以下后台代码示例处理 SelectionChanged 事件引发的事件。 每个自定义方法从 ListBox获取输入，将值分析为 Double，并将该值应用于指定的与宽度相关的属性。 宽度值也会转换为字符串，并写入各种 TextBlock 元素（所选 XAML 中未显示这些元素的定义）。

private void changeWidth(object sender, SelectionChangedEventArgs args)

{

ListBoxItem li = ((sender as ListBox).SelectedItem as ListBoxItem);

Double sz1 = Double.Parse(li.Content.ToString());

rect1.Width = sz1;

rect1.UpdateLayout();

txt1.Text = "ActualWidth is set to " + rect1.ActualWidth;

txt2.Text = "Width is set to " + rect1.Width;

txt3.Text = "MinWidth is set to " + rect1.MinWidth;

txt4.Text = "MaxWidth is set to " + rect1.MaxWidth;

}

private void changeMinWidth(object sender, SelectionChangedEventArgs args)

{

ListBoxItem li = ((sender as ListBox).SelectedItem as ListBoxItem);

Double sz1 = Double.Parse(li.Content.ToString());

rect1.MinWidth = sz1;

rect1.UpdateLayout();

txt1.Text = "ActualWidth is set to " + rect1.ActualWidth;

txt2.Text = "Width is set to " + rect1.Width;

txt3.Text = "MinWidth is set to " + rect1.MinWidth;

txt4.Text = "MaxWidth is set to " + rect1.MaxWidth;

}

private void changeMaxWidth(object sender, SelectionChangedEventArgs args)

{

ListBoxItem li = ((sender as ListBox).SelectedItem as ListBoxItem);

Double sz1 = Double.Parse(li.Content.ToString());

rect1.MaxWidth = sz1;

rect1.UpdateLayout();

txt1.Text = "ActualWidth is set to " + rect1.ActualWidth;

txt2.Text = "Width is set to " + rect1.Width;

txt3.Text = "MinWidth is set to " + rect1.MinWidth;

txt4.Text = "MaxWidth is set to " + rect1.MaxWidth;

}

Private Sub changeWidth(ByVal sender As Object, ByVal args As SelectionChangedEventArgs)

Dim li As ListBoxItem = CType(CType(sender, ListBox).SelectedItem, ListBoxItem)

Dim sz1 As Double = Double.Parse(li.Content.ToString())

rect1.Width = sz1

rect1.UpdateLayout()

txt1.Text = "ActualWidth is set to " + rect1.ActualWidth.ToString

txt2.Text = "Width is set to " + rect1.Width.ToString

txt3.Text = "MinWidth is set to " + rect1.MinWidth.ToString

txt4.Text = "MaxWidth is set to " + rect1.MaxWidth.ToString

End Sub

Private Sub changeMinWidth(ByVal sender As Object, ByVal args As SelectionChangedEventArgs)

Dim li As ListBoxItem = CType(CType(sender, ListBox).SelectedItem, ListBoxItem)

Dim sz1 As Double = Double.Parse(li.Content.ToString())

rect1.MinWidth = sz1

rect1.UpdateLayout()

txt1.Text = "ActualWidth is set to " + rect1.ActualWidth.ToString

txt2.Text = "Width is set to " + rect1.Width.ToString

txt3.Text = "MinWidth is set to " + rect1.MinWidth.ToString

txt4.Text = "MaxWidth is set to " + rect1.MaxWidth.ToString

End Sub

Private Sub changeMaxWidth(ByVal sender As Object, ByVal args As SelectionChangedEventArgs)

Dim li As ListBoxItem = CType(CType(sender, ListBox).SelectedItem, ListBoxItem)

Dim sz1 As Double = Double.Parse(li.Content.ToString())

rect1.MaxWidth = sz1

rect1.UpdateLayout()

txt1.Text = "ActualWidth is set to " + rect1.ActualWidth.ToString

txt2.Text = "Width is set to " + rect1.Width.ToString

txt3.Text = "MinWidth is set to " + rect1.MinWidth.ToString

txt4.Text = "MaxWidth is set to " + rect1.MaxWidth.ToString

End Sub

有关完整示例，请参阅 宽度属性比较示例。

另请参阅

ListBox

FrameworkElement

ActualWidth

MaxWidth

MinWidth

Width

面板概述

设置元素的高度属性

宽度属性比较示例