Question

我在WPF应用程序中有TextBlock。

此的{Text，Width，Height，TextWrapping，FontSize，FontWeight，FontFamily）属性TextBlock是动态的（由用户在运行时输入）。

每次用户更改以前的某个属性时，Content的{{1}}属性都会在运行时更改。（一切都好，直到这里）

现在，我需要根据之前指定的属性获取TextBlock的行这意味着我需要TextBlock算法产生的行。

换句话说，我需要一个单独的字符串中的每一行，或者我需要一个带Scape序列TextWrapping的字符串。

有任何想法吗？

Answer 1

如果没有公开的方式，我会感到惊讶（尽管人们从不知道，尤其是WPF）。
确实看起来TextPointer class是我们的朋友，所以这里有一个基于TextBlock.ContentStart，TextPointer.GetLineStartPosition和TextPointer.GetOffsetToPosition的解决方案：

public static class TextUtils
{
    public static IEnumerable<string> GetLines(this TextBlock source)
    {
        var text = source.Text;
        int offset = 0;
        TextPointer lineStart = source.ContentStart.GetPositionAtOffset(1, LogicalDirection.Forward);
        do
        {
            TextPointer lineEnd = lineStart != null ? lineStart.GetLineStartPosition(1) : null;
            int length = lineEnd != null ? lineStart.GetOffsetToPosition(lineEnd) : text.Length - offset;
            yield return text.Substring(offset, length);
            offset += length;
            lineStart = lineEnd;
        }
        while (lineStart != null);
    }
}

这里没有太多要解释的内容获取该行的起始位置，减去前一行的起始位置以获得行文本的长度，这里我们是。
唯一棘手的（或非显而易见的）部分是因为设计 ContentStart 需要将The TextPointer returned by this property always has its LogicalDirection set to Backward.偏移一个，所以我们需要获取指针相同的（！？）位置，但 LogicalDirection set to Forward ，无论这意味着什么。

Answer 2

使用FormattedText类，可以首先创建格式化文本并评估其大小，以便您知道第一步所需的空间，如果时间过长，则需要分开分开。

然后在第二步中，可以绘制它。

以下方法可能会在DrawingContext对象上发生任何事情：

protected override void OnRender(System.Windows.Media.DrawingContext dc)

以下是 CustomControl 解决方案：

[ContentProperty("Text")]
public class TextBlockLineSplitter : FrameworkElement
{
    public FontWeight FontWeight
    {
        get { return (FontWeight)GetValue(FontWeightProperty); }
        set { SetValue(FontWeightProperty, value); }
    }

    public static readonly DependencyProperty FontWeightProperty =
        DependencyProperty.Register("FontWeight", typeof(FontWeight), typeof(TextBlockLineSplitter), new PropertyMetadata(FontWeight.FromOpenTypeWeight(400)));

    public double FontSize
    {
        get { return (double)GetValue(FontSizeProperty); }
        set { SetValue(FontSizeProperty, value); }
    }

    public static readonly DependencyProperty FontSizeProperty =
        DependencyProperty.Register("FontSize", typeof(double), typeof(TextBlockLineSplitter), new PropertyMetadata(10.0));

    public String FontFamily
    {
        get { return (String)GetValue(FontFamilyProperty); }
        set { SetValue(FontFamilyProperty, value); }
    }

    public static readonly DependencyProperty FontFamilyProperty =
        DependencyProperty.Register("FontFamily", typeof(String), typeof(TextBlockLineSplitter), new PropertyMetadata("Arial"));

    public String Text
    {
        get { return (String)GetValue(TextProperty); }
        set { SetValue(TextProperty, value); }
    }

    public static readonly DependencyProperty TextProperty =
        DependencyProperty.Register("Text", typeof(String), typeof(TextBlockLineSplitter), new PropertyMetadata(null));

    public double Interline
    {
        get { return (double)GetValue(InterlineProperty); }
        set { SetValue(InterlineProperty, value); }
    }

    public static readonly DependencyProperty InterlineProperty =
        DependencyProperty.Register("Interline", typeof(double), typeof(TextBlockLineSplitter), new PropertyMetadata(3.0));

    public List<String> Lines
    {
        get { return (List<String>)GetValue(LinesProperty); }
        set { SetValue(LinesProperty, value); }
    }

    public static readonly DependencyProperty LinesProperty =
        DependencyProperty.Register("Lines", typeof(List<String>), typeof(TextBlockLineSplitter), new PropertyMetadata(new List<String>()));

    protected override void OnRender(DrawingContext drawingContext)
    {
        base.OnRender(drawingContext);
        Lines.Clear();
        if (!String.IsNullOrWhiteSpace(Text))
        {
            string remainingText = Text;
            string textToDisplay = Text;
            double availableWidth = ActualWidth;
            Point drawingPoint = new Point();

            // put clip for preventing writing out the textblock
            drawingContext.PushClip(new RectangleGeometry(new Rect(new Point(0, 0), new Point(ActualWidth, ActualHeight))));
            FormattedText formattedText = null;

            // have an initial guess :
            formattedText = new FormattedText(textToDisplay,
                Thread.CurrentThread.CurrentUICulture,
                FlowDirection.LeftToRight,
                new Typeface(FontFamily),
                FontSize,
                Brushes.Black);
            double estimatedNumberOfCharInLines = textToDisplay.Length * availableWidth / formattedText.Width;

            while (!String.IsNullOrEmpty(remainingText))
            {
                // Add 15%
                double currentEstimatedNumberOfCharInLines = Math.Min(remainingText.Length, estimatedNumberOfCharInLines * 1.15);
                do
                {
                    textToDisplay = remainingText.Substring(0, (int)(currentEstimatedNumberOfCharInLines));

                    formattedText = new FormattedText(textToDisplay,
                        Thread.CurrentThread.CurrentUICulture,
                        FlowDirection.LeftToRight,
                        new Typeface(FontFamily),
                        FontSize,
                        Brushes.Black);
                    currentEstimatedNumberOfCharInLines -= 1;
                } while (formattedText.Width > availableWidth);

                Lines.Add(textToDisplay);
                System.Diagnostics.Debug.WriteLine(textToDisplay);
                System.Diagnostics.Debug.WriteLine(remainingText.Length);
                drawingContext.DrawText(formattedText, drawingPoint);
                if (remainingText.Length > textToDisplay.Length)
                    remainingText = remainingText.Substring(textToDisplay.Length);
                else
                    remainingText = String.Empty;
                drawingPoint.Y += formattedText.Height + Interline;
            }
            foreach (var line in Lines)
            {
                System.Diagnostics.Debug.WriteLine(line);
            }
        }
    }
}

该控件的使用（此处的边框显示有效剪裁）：

<Border BorderThickness="1" BorderBrush="Red" Height="200" VerticalAlignment="Top">
    <local:TextBlockLineSplitter>Alice was beginning to get very tired of sitting by her sister on the bank, and of having nothing to do. Once or twice she had peeped into the book her sister was reading, but it had no pictures or conversations in it, &quot;and what is the use of a book,&quot; thought Alice, ...</local:TextBlockLineSplitter>
</Border>

Answer 3

如果不是问题，你可以在TextBlock控件上使用反射（它当然知道如何包装字符串）。如果你没有使用MVVM，我想它适合你。

首先，我创建了一个用于测试我的解决方案的最小窗口：

<Window x:Class="WpfApplication1.MainWindow" Name="win"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="600" Width="600">

    <StackPanel>
        <TextBlock Name="txt"  Text="Lorem ipsum dolor sit amet, consectetur adipisci elit, sed eiusmod tempor incidunt ut labore et dolore magna aliqua." Margin="20" 
                   TextWrapping="Wrap" />
        <Button Click="OnCalculateClick" Content="Calculate ROWS" Margin="5" />

        <TextBox Name="Result" Height="100" />
    </StackPanel>

</Window>

现在让我们看一下代码隐藏的最重要部分：

private void OnCalculateClick(object sender, EventArgs args)
{
    int start = 0;
    int length = 0;

    List<string> tokens = new List<string>();

    foreach (object lineMetrics in GetLineMetrics(txt))
    {
        length = GetLength(lineMetrics);
        tokens.Add(txt.Text.Substring(start, length));

        start += length;
    }

    Result.Text = String.Join(Environment.NewLine, tokens);
}

private int GetLength(object lineMetrics)
{
    PropertyInfo propertyInfo = lineMetrics.GetType().GetProperty("Length", BindingFlags.Instance
        | BindingFlags.NonPublic);

    return (int)propertyInfo.GetValue(lineMetrics, null);
}

private IEnumerable GetLineMetrics(TextBlock textBlock)
{
    ArrayList metrics = new ArrayList();
    FieldInfo fieldInfo = typeof(TextBlock).GetField("_firstLine", BindingFlags.Instance
        | BindingFlags.NonPublic);
    metrics.Add(fieldInfo.GetValue(textBlock));

    fieldInfo = typeof(TextBlock).GetField("_subsequentLines", BindingFlags.Instance
        | BindingFlags.NonPublic);

    object nextLines = fieldInfo.GetValue(textBlock);
    if (nextLines != null)
    {
        metrics.AddRange((ICollection)nextLines);
    }

    return metrics;
}

GetLineMetrics方法检索LineMetrics集合（内部对象，因此我不能直接使用它）。此对象具有名为“Length”的属性，该属性包含您需要的信息。因此GetLength方法只读取此属性的值。

行存储在名为tokens的列表中，并使用TextBox控件显示（仅用于立即反馈）。

我希望我的样本可以帮助您完成任务。

根据TextWrapping属性获取TextBlock的行？

3 个答案: