wpf - 从 TextBlock 获取显示的文本

Question

我有一个像这样定义的简单 TextBlock

<StackPanel>
    <Border Width="106"
            Height="25"
            Margin="6"
            BorderBrush="Black"
            BorderThickness="1"
            HorizontalAlignment="Left">
        <TextBlock Name="myTextBlock"
                   TextTrimming="CharacterEllipsis"
                   Text="TextBlock: Displayed text"/>
    </Border>
</StackPanel>

哪个输出像这样



这会让我“TextBlock:显示的文本”

string text = myTextBlock.Text;

但是有没有办法获得实际显示在屏幕上的文本？
意思是“文本块:显示...”

谢谢

Answer 1

您可以通过首先检索 Drawing 来做到这一点。表示 TextBlock 外观的对象在视觉树中，然后走那个寻找 GlyphRunDrawing项目 - 这些将包含屏幕上实际呈现的文本。这是一个非常粗略和准备好的实现:

private void button1_Click(object sender, RoutedEventArgs e)
{
    Drawing textBlockDrawing = VisualTreeHelper.GetDrawing(myTextBlock);
    var sb = new StringBuilder();
    WalkDrawingForText(sb, textBlockDrawing);

    Debug.WriteLine(sb.ToString());
}

private static void WalkDrawingForText(StringBuilder sb, Drawing d)
{
    var glyphs = d as GlyphRunDrawing;
    if (glyphs != null)
    {
        sb.Append(glyphs.GlyphRun.Characters.ToArray());
    }
    else
    {
        var g = d as DrawingGroup;
        if (g != null)
        {
            foreach (Drawing child in g.Children)
            {
                WalkDrawingForText(sb, child);
            }
        }
    }
}

这是我刚刚编写的一个小测试工具的直接摘录 - 第一种方法是一个按钮单击处理程序，只是为了便于实验。

它使用 VisualTreeHelper得到渲染 Drawing为 TextBlock - 这只在事物已经被顺便渲染的情况下才有效。然后是 WalkDrawingForText方法完成实际工作 - 它只是遍历 Drawing树寻找文本。

这不是非常聪明 - 它假设 GlyphRunDrawing对象按您想要的顺序出现。对于您的特定示例，它确实如此 - 我们得到一个 GlyphRunDrawing包含被截断的文本，然后是包含省略号的第二个文本。 (顺便说一句，它只是一个 unicode 字符 - 代码点 2026，如果这个编辑器让我粘贴 unicode 字符，它是“...”。它不是三个单独的句点。)

如果你想让它更健壮，你需要计算出所有这些 GlyphRunDrawing 的位置。对象，并对它们进行排序，以便按照它们出现的顺序处理它们，而不是仅仅希望 WPF 碰巧按该顺序生成它们。

更新添加:

这是位置感知示例的外观草图。虽然这有点狭隘 - 它假设从左到右阅读文本。对于国际化解决方案，您需要更复杂的东西。

private string GetTextFromVisual(Visual v)
{
    Drawing textBlockDrawing = VisualTreeHelper.GetDrawing(v);
    var glyphs = new List<PositionedGlyphs>();

    WalkDrawingForGlyphRuns(glyphs, Transform.Identity, textBlockDrawing);

    // Round vertical position, to provide some tolerance for rounding errors
    // in position calculation. Not totally robust - would be better to
    // identify lines, but that would complicate the example...
    var glyphsOrderedByPosition = from glyph in glyphs
                                    let roundedBaselineY = Math.Round(glyph.Position.Y, 1)
                                    orderby roundedBaselineY ascending, glyph.Position.X ascending
                                    select new string(glyph.Glyphs.GlyphRun.Characters.ToArray());

    return string.Concat(glyphsOrderedByPosition);
}

[DebuggerDisplay("{Position}")]
public struct PositionedGlyphs
{
    public PositionedGlyphs(Point position, GlyphRunDrawing grd)
    {
        this.Position = position;
        this.Glyphs = grd;
    }
    public readonly Point Position;
    public readonly GlyphRunDrawing Glyphs;
}

private static void WalkDrawingForGlyphRuns(List<PositionedGlyphs> glyphList, Transform tx, Drawing d)
{
    var glyphs = d as GlyphRunDrawing;
    if (glyphs != null)
    {
        var textOrigin = glyphs.GlyphRun.BaselineOrigin;
        Point glyphPosition = tx.Transform(textOrigin);
        glyphList.Add(new PositionedGlyphs(glyphPosition, glyphs));
    }
    else
    {
        var g = d as DrawingGroup;
        if (g != null)
        {
            // Drawing groups are allowed to transform their children, so we need to
            // keep a running accumulated transform for where we are in the tree.
            Matrix current = tx.Value;
            if (g.Transform != null)
            {
                // Note, Matrix is a struct, so this modifies our local copy without
                // affecting the one in the 'tx' Transforms.
                current.Append(g.Transform.Value);
            }
            var accumulatedTransform = new MatrixTransform(current);
            foreach (Drawing child in g.Children)
            {
                WalkDrawingForGlyphRuns(glyphList, accumulatedTransform, child);
            }
        }
    }
}