如果文本太长，如何自动显示工具提示？

Question

在 Windows 应用商店应用程序中，我有以下 TextBlock：

        <TextBlock Text="Seriously long text for the purpose of showing tooltip"
                   TextTrimming="CharacterEllipsis" />

当文本太长而无法在没有省略号的情况下显示时，如何自动显示工具提示？

Answer 1

这是我的解决方案，基于this和this。

首先，创建一个附加属性以启用自动工具提示：

public static class TextBlockUtils {
    public static readonly DependencyProperty AutoTooltipProperty =
        DependencyProperty.RegisterAttached ("AutoTooltip", typeof (bool), typeof (TextBlockUtils),
                                             new PropertyMetadata (false, OnAutoTooltipPropertyChanged));

    public static void SetAutoTooltip (DependencyObject d, bool value) {
        d.SetValue (AutoTooltipProperty, value);
    }

    public static bool GetAutoTooltip (DependencyObject d) {
        return (bool) d.GetValue (AutoTooltipProperty);
    }

    private static void OnAutoTooltipPropertyChanged (DependencyObject d, DependencyPropertyChangedEventArgs e) {
        var tb = d as TextBlock;
        if (tb != null) {
            bool newValue = (bool) e.NewValue;
            if (newValue) {
                SetTooltipBasedOnTrimmingState (tb);
                tb.SizeChanged += OnTextBlockSizeChanged;
            }
            else {
                tb.SizeChanged -= OnTextBlockSizeChanged;
            }
        }
    }

    private static void OnTextBlockSizeChanged (object sender, SizeChangedEventArgs e) {
        var tb = sender as TextBlock;
        if (tb != null) {
            SetTooltipBasedOnTrimmingState (tb);
        }
    }

    private static void SetTooltipBasedOnTrimmingState (TextBlock tb) {
        bool isTextTrimmed = tb.ActualWidth < tb.DesiredSize.Width;
        ToolTipService.SetToolTip (tb, isTextTrimmed ? tb.Text : null);
    }
}

然后在 XAML 中使用它，如下所示：

<TextBlock Content="long text"
           TextTrimming="CharacterEllipsis"
           TextBlockUtils.AutoTooltip="True" />

仅当文本块被修剪时才会显示工具提示。