简明扼要的问题:
是否可以测量未选择Tab的内容?
问题摘要:
想象一下,你有一个带有两个标签的TabControl。第一个选项卡包含一个带有TextBlock的Grid。您选择第二个选项卡。经过一段时间后,TextBlock的Text字段变为非常长的字符串。您希望在可见之前测量第一个标签内容的大小。
如果您只是执行一个度量,它将无法捕获字符串已更改的事实 - 您可以在WPF Visualizer中看到TextBlock在其Text字段中具有新字符串,但TextBlock拒绝重新测量。如果直接测量字符串,可以检测新的所需大小,但这不是一个好的解决方案;我希望能够衡量第一个标签的总内容,而不仅仅是字符串。
无论如何,为长示例代码道歉,这很难进一步减少。当窗口出现时,代码等待两秒钟,然后交换选项卡。然后它改变字符串。测量循环在检测到字符串大小更改时将背景更改为蓝色,并在检测到实际内容大小更改时将其更改为红色。红色仅在切换标签时发生,但我希望能够在不必切换回第一个标签的情况下发生红色。
代码背后:
public MainWindow()
{
InitializeComponent();
// this worker waits a bit so the first tab renders,
// then it switches tabs and changes the string.
BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += delegate
{
Thread.Sleep(2000);
Application.Current.Dispatcher.BeginInvoke(new Action(delegate
{
TestTabControl.SelectedIndex = 1;
TestBlock.Text = "This is a long string that ought to change the measure of the textblock to sizes never before seen by human eyes";
this.Background = Brushes.Green;
}));
};
worker.RunWorkerAsync();
// This worker constantly measures the text block
worker = new BackgroundWorker();
worker.DoWork += delegate
{
while (true)
{
if (Application.Current != null)
{
Application.Current.Dispatcher.BeginInvoke(new Action(delegate
{
MeasureFirstTab();
}));
}
else
{
break;
}
Thread.Sleep(100);
}
};
worker.RunWorkerAsync();
}
// Turn the background red when the tab width changes
public void MeasureFirstTab()
{
FirstTabContent.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
if (MeasureString(TestBlock.Text).Width > 500)
{
this.Background = Brushes.Blue;
}
if (FirstTabContent.DesiredSize.Width > 500)
{
this.Background = Brushes.Red;
}
}
private Size MeasureString(string candidate)
{
var formattedText = new FormattedText(
candidate,
CultureInfo.CurrentUICulture,
FlowDirection.LeftToRight,
new Typeface(TestBlock.FontFamily, TestBlock.FontStyle, TestBlock.FontWeight, TestBlock.FontStretch),
TestBlock.FontSize,
Brushes.Black);
return new Size(formattedText.Width, formattedText.Height);
}
}
XAML:
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<TabControl Name="TestTabControl">
<TabItem Header="Changes">
<Grid Name="FirstTabContent">
<TextBlock Name="TestBlock" Text="small"/>
</Grid>
</TabItem>
<TabItem Header="Short">
<TextBlock Text="Short"/>
</TabItem>
</TabControl>
</Grid>
答案 0 :(得分:0)
回答后人以及将来搜集这个问题的任何人。
正如我对OP的评论所述,TabControl虚拟化了未选中的标签,这显然导致测量通过仅计算之前的所需大小。
因此,解决方案是从选项卡项中删除内容,将其添加到网格,测量内容,然后将其添加回选项卡。
以下是新的衡量标准代码:
// Turn the background red when the tab width changes
public void MeasureFirstTab()
{
// Remember the previous selected item
object selectedItem = TestTabControl.SelectedItem;
Grid measureBox = new Grid();
UIElement content;
// Iterate through all items
foreach (TabItem obj in TestTabControl.Items)
{
// Get the tab content into the grid
TestTabControl.SelectedItem = obj;
content = (UIElement)obj.Content;
obj.Content = null;
measureBox.Children.Add(content);
// Measure the content
content.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
if (content.DesiredSize.Width > 500)
{
this.Background = Brushes.Red;
}
// Return the content to its rightful owner
measureBox.Children.Clear();
obj.Content = content;
}
// Reset the tab control
TestTabControl.SelectedItem = selectedItem;
}