有很多问题（例如：1、2、3、4、5）询问如何将字符串截断为所需数量的字符。但我想要截断一段文本以适合容器。（即：以像素为单位裁剪字符串，而不是字符）。
如果您使用 WPF，这很容易，但在 WinForms 中就不那么容易了......
那么：如何截断字符串以使其适合容器？
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经过一天的编码，我找到了一个解决方案，我想与社区分享。
首先：字符串或winforms TextBox没有本机截断功能。如果使用标签，则可以使用 AutoEllipsis 属性。
仅供参考：省略号是由三个点组成的标点符号。即：……</p>
这就是我做这个的原因：
public static class Extensions
{
/// <summary>
/// Truncates the TextBox.Text property so it will fit in the TextBox.
/// </summary>
static public void Truncate(this TextBox textBox)
{
//Determine direction of truncation
bool direction = false;
if (textBox.TextAlign == HorizontalAlignment.Right) direction = true;
//Get text
string truncatedText = textBox.Text;
//Truncate text
truncatedText = truncatedText.Truncate(textBox.Font, textBox.Width, direction);
//If text truncated
if (truncatedText != textBox.Text)
{
//Set textBox text
textBox.Text = truncatedText;
//After setting the text, the cursor position changes. Here we set the location of the cursor manually.
//First we determine the position, the default value applies to direction = left.
//This position is when the cursor needs to be behind the last char. (Example:"…My Text|");
int position = 0;
//If the truncation direction is to the right the position should be before the ellipsis
if (!direction)
{
//This position is when the cursor needs to be before the last char (which would be the ellipsis). (Example:"My Text|…");
position = 1;
}
//Set the cursor position
textBox.Select(textBox.Text.Length - position, 0);
}
}
/// <summary>
/// Truncates the string to be smaller than the desired width.
/// </summary>
/// <param name="font">The font used to determine the size of the string.</param>
/// <param name="width">The maximum size the string should be after truncating.</param>
/// <param name="direction">The direction of the truncation. True for left (…ext), False for right(Tex…).</param>
static public string Truncate(this string text, Font font, int width, bool direction)
{
string truncatedText, returnText;
int charIndex = 0;
bool truncated = false;
//When the user is typing and the truncation happens in a TextChanged event, already typed text could get lost.
//Example: Imagine that the string "Hello Worl" would truncate if we add 'd'. Depending on the font the output
//could be: "Hello Wor…" (notice the 'l' is missing). This is an undesired effect.
//To prevent this from happening the ellipsis is included in the initial sizecheck.
//At this point, the direction is not important so we place ellipsis behind the text.
truncatedText = text + "…";
//Get the size of the string in pixels.
SizeF size = MeasureString(truncatedText, font);
//Do while the string is bigger than the desired width.
while (size.Width > width)
{
//Go to next char
charIndex++;
//If the character index is larger than or equal to the length of the text, the truncation is unachievable.
if (charIndex >= text.Length)
{
//Truncation is unachievable!
//Throw exception so the user knows what's going on.
throw new IndexOutOfRangeException("The desired width of the string is too small to truncate to.");
}
else
{
//Truncation is still applicable!
//Raise the flag, indicating that text is truncated.
truncated = true;
//Check which way to text should be truncated to, then remove one char and add an ellipsis.
if (direction)
{
//Truncate to the left. Add ellipsis and remove from the left.
truncatedText = "…" + text.Substring(charIndex);
}
else
{
//Truncate to the right. Remove from the right and add the ellipsis.
truncatedText = text.Substring(0, text.Length - charIndex) + "…";
}
//Measure the string again.
size = MeasureString(truncatedText, font);
}
}
//If the text got truncated, change the return value to the truncated text.
if (truncated) returnText = truncatedText;
else returnText = text;
//Return the desired text.
return returnText;
}
/// <summary>
/// Measures the size of this string object.
/// </summary>
/// <param name="text">The string that will be measured.</param>
/// <param name="font">The font that will be used to measure to size of the string.</param>
/// <returns>A SizeF object containing the height and size of the string.</returns>
static private SizeF MeasureString(String text, Font font)
{
//To measure the string we use the Graphics.MeasureString function, which is a method that can be called from a PaintEventArgs instance.
//To call the constructor of the PaintEventArgs class, we must pass a Graphics object. We'll use a PictureBox object to achieve this.
PictureBox pb = new PictureBox();
//Create the PaintEventArgs with the correct parameters.
PaintEventArgs pea = new PaintEventArgs(pb.CreateGraphics(), new System.Drawing.Rectangle());
pea.Graphics.PageUnit = GraphicsUnit.Pixel;
pea.Graphics.PageScale = 1;
//Call the MeasureString method. This methods calculates what the height and width of a string would be, given the specified font.
SizeF size = pea.Graphics.MeasureString(text, font);
//Return the SizeF object.
return size;
}
}
用法： 这是一个类，您可以在包含您的 winforms 表单的命名空间中复制和粘贴。确保包含“ using System.Drawing; ”
该类有两个扩展方法，都称为 Truncate。基本上你现在可以这样做：
public void textBox1_TextChanged(object sender, EventArgs e)
{
textBox1.Truncate();
}
您现在可以在 textBox1 中输入内容，如果需要，它会自动截断您的字符串以适合 textBox 并添加省略号。
概述： 该类目前包含 3 个方法：
- 截断（文本框的扩展）
- 截断（字符串的扩展）
- 测量字符串
截断（文本框的扩展）
此方法将自动截断 TextBox.Text 属性。截断的方向由 TextAlign 属性决定。（例如：“左对齐截断...”、“...右对齐截断”。）请注意：此方法可能需要进行一些更改才能与其他书写系统（例如希伯来语或阿拉伯语）一起使用。
截断（字符串的扩展）
为了使用此方法，您必须传递两个参数：字体和所需的宽度。字体用于计算字符串的宽度，所需宽度作为截断后允许的最大宽度。
测量字符串
此方法在代码片段中是私有的。所以如果你想使用它，你必须先把它改成public。此方法用于测量字符串的高度和宽度（以像素为单位）。它需要两个参数：要测量的文本和文本的字体。
我希望我能帮助某人。也许还有其他方法可以做到这一点，我找到了 Hans Passant 的这个答案，它截断了 ToolTipStatusLabel，这令人印象深刻。我的 .NET 技能与 Hans Passant 相去甚远，所以我还没有设法将该代码转换为使用 TextBox 之类的东西……但如果你成功了，或者有其他解决方案，我很乐意看到它！:)
于 2013-07-15T12:26:55.043 回答
1
我测试了 Jordy 的代码并将结果与我的这段代码进行了比较，没有区别，它们都可以修剪/截断，但在某些情况下效果不佳，这可能是测量的大小MeasureString()不准确。我知道这段代码只是一个简化版本，如果有人关心它并使用它，我会在这里发布它，因为它很短并且我测试过：与 Jordy 的代码相比，这段代码如何修剪/截断字符串没有区别当然，他的代码是某种完整版本，支持 3 种方法。
public static class TextBoxExtension
{
public static void Trim(this TextBox text){
string txt = text.Text;
if (txt.Length == 0 || text.Width == 0) return;
int i = txt.Length;
while (TextRenderer.MeasureText(txt + "...", text.Font).Width > text.Width)
{
txt = text.Text.Substring(0, --i);
if (i == 0) break;
}
text.Text = txt + "...";
}
//You can implement more methods such as receiving a string with font,... and returning the truncated/trimmed version.
}
于 2013-07-15T15:44:44.640 回答