当字符串太长时，以“…”打断文本块中的文本

Question

我在Windows Phone 8应用程序中使用包含许多元素的长列表选择器。 每个项目都有一个文本块，并且每个项目的文本可以从几个字母到很多单词。 我想将文本保持为一行，因此将TextWrapping属性设置为“ NoWrap”。 我想添加“ ...”并裁剪文本，如果它太长而无法在屏幕上显示。 到目前为止，我尝试使用每个TextBlock的load事件并减少文本，直到它适合屏幕为止。 但是，当列表中包含许多元素时，加载事件不会针对所有文本块激活。 是否有解决此问题的正确方法？

    private void TextBlock_Loaded_1(object sender, RoutedEventArgs e)
    {
        TextBlock txt = sender as TextBlock;
        if (txt == null)
            return;

        if (txt.ActualWidth > 300)
        {
            while (txt.Text.Length > 4 && txt.ActualWidth > 290)
                txt.Text = txt.Text.Substring(0, txt.Text.Length - 4);
            txt.Text = txt.Text.Substring(0, txt.Text.Length - 3);

            txt.Text = txt.Text.Trim(new Char[] { ' ', ',' }) + "...";

        }
    }

Answer 1

这是如何实现此目的的Converter示例：

using System;
using System.Globalization;
using System.Windows.Data;

namespace PhoneApp2
{
    public class TextLengthConverter: IValueConverter
    {
        #region Implementation of IValueConverter

        /// <summary>
        /// Modifies the source data before passing it to the target for display in the UI.
        /// </summary>
        /// <returns>
        /// The value to be passed to the target dependency property.
        /// </returns>
        /// <param name="value">The source data being passed to the target.</param><param name="targetType">The <see cref="T:System.Type"/> of data expected by the target dependency property.</param><param name="parameter">An optional parameter to be used in the converter logic.</param><param name="culture">The culture of the conversion.</param>
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (value is string)
            {
                int desiredLength;
                if (int.TryParse(parameter.ToString(), out desiredLength))
                {
                    if (desiredLength > 0)
                    {
                        string textIn = value as string;
                        if (textIn.Length > desiredLength // Make sure the truncation is actually needed.
                            && textIn.Length > 3) // Make sure the length if the textIn is longer than the dots so 'something' is shown before the dots.
                        {
                            return textIn.Substring(0, desiredLength - 3) + "...";
                        }
                    }
                }
            }
            return value;
        }

        /// <summary>
        /// Modifies the target data before passing it to the source object.  This method is called only in <see cref="F:System.Windows.Data.BindingMode.TwoWay"/> bindings.
        /// </summary>
        /// <returns>
        /// The value to be passed to the source object.
        /// </returns>
        /// <param name="value">The target data being passed to the source.</param><param name="targetType">The <see cref="T:System.Type"/> of data expected by the source object.</param><param name="parameter">An optional parameter to be used in the converter logic.</param><param name="culture">The culture of the conversion.</param>
        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }

        #endregion
    }
}

要在页面中使用它，请添加资源条目，如下所示：

<phone:PhoneApplicationPage.Resources>
    <PhoneApp2:TextLengthConverter x:Key="TextLengthConverter"/>
</phone:PhoneApplicationPage.Resources>

并将其附加到您的绑定文本中：

<TextBlock Text="{Binding BoundText, Converter={StaticResource TextLengthConverter}, ConverterParameter=4}"/>

您可以将其添加到转换器集合中，这是一个不错的，可重用的解决方案。