wp7超大文本显示控件 垂直滚动

wp7中textblock显示有文本数量限制。貌似超过2048个字符就不显示了。

从国外网站找了一个控件，实现加载大量文本显示，并且垂直滚动浏览。

实现原理其实挺简单的，就是动态创建多个textblock控件，每个控件显示部分内容。

有点，加载大量文本时，垂直方向滚动浏览，用户体验度较高（个人感觉比一页页翻页舒服多了）

缺点，由于加载了多个控件，所以加载速度慢（与文本长度有关），这也许时微软限制显示数量的原因。

上代码：

using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.IO;
using System.Text;

namespace wwb.Phone.Ctrls
{
public class ScrollableTextBlock : Control
{
private StackPanel stackPanel;
private TextBlock measureBlock;

public ScrollableTextBlock()
{
// Get the style from generic.xaml
this.DefaultStyleKey = typeof(ScrollableTextBlock);
}

public static readonly DependencyProperty TextProperty =
DependencyProperty.Register(
"Text",
typeof(string),
typeof(ScrollableTextBlock),
new PropertyMetadata("ScrollableTextBlock", OnTextPropertyChanged));

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

private static void OnTextPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
ScrollableTextBlock source = (ScrollableTextBlock)d;
string value = (string)e.NewValue;
source.ParseText(value);
}

public override void OnApplyTemplate()
{
base.OnApplyTemplate();
this.stackPanel = this.GetTemplateChild("StackPanel") as StackPanel;
this.ParseText(this.Text);
}

private void ParseTextHide(string value)
{
if (this.stackPanel == null)
{
return;
}
// Clear previous TextBlocks
this.stackPanel.Children.Clear();
// Calculate max char count
int maxTexCount = this.GetMaxTextSize();

if (value.Length < maxTexCount)
{
TextBlock textBlock = this.GetTextBlock();
textBlock.Text = value;
this.stackPanel.Children.Add(textBlock);
}
else
{
int n = value.Length / maxTexCount;
int start = 0;

// Add textblocks
for (int i = 0; i < n; i++)
{
TextBlock textBlock = this.GetTextBlock();
textBlock.Text = value.Substring(start, maxTexCount);
this.stackPanel.Children.Add(textBlock);
start = maxTexCount;
}

// Pickup the leftover text
if (value.Length % maxTexCount > 0)
{
TextBlock textBlock = this.GetTextBlock();
textBlock.Text = value.Substring(maxTexCount * n, value.Length - maxTexCount * n);
this.stackPanel.Children.Add(textBlock);
}
}
}

private void ParseText(string value)
{
StringReader reader = new StringReader(value);

if (this.stackPanel == null)
{
return;
}
// Clear previous TextBlocks
this.stackPanel.Children.Clear();
// Calculate max char count
int maxTexCount = this.GetMaxTextSize();

if (value.Length < maxTexCount)
{
TextBlock textBlock = this.GetTextBlock();
textBlock.Text = value;
this.stackPanel.Children.Add(textBlock);
}
else
{
string line = "";

while (reader.Peek() > 0)
{
line = reader.ReadLine();
ParseLine(line);
}

}

}

private void ParseLine(string line)
{
int lineCount = 0;
int maxLineCount = GetMaxLineCount();
string tempLine = line;
StringBuilder sbLine = new StringBuilder();

while (lineCount < maxLineCount)
{
int charactersFitted = MeasureString(tempLine, (int)this.Width);
string leftSide = tempLine.Substring(0, charactersFitted);
sbLine.Append(leftSide);
tempLine = tempLine.Substring(charactersFitted, tempLine.Length - (charactersFitted));
lineCount++;
}

TextBlock textBlock = this.GetTextBlock();
textBlock.Text = sbLine.ToString();
this.stackPanel.Children.Add(textBlock);

if (tempLine.Length > 0)
{
ParseLine(tempLine);
}
}

private int MeasureString(string text, int desWidth)
{

int nWidth = 0;
int charactersFitted = 0;

StringBuilder sb = new StringBuilder();

//get original size
Size size = MeasureString(text);

if (size.Width > desWidth)
{
string[] words = text.Split(' ');
sb.Append(words[0]);

for (int i = 1; i < words.Length; i++)
{
sb.Append(" " + words[i]);
nWidth = (int)MeasureString(sb.ToString()).Width;

if (nWidth > desWidth)
{

sb.Remove(sb.Length - words[i].Length, words[i].Length);
break;
}
}

charactersFitted = sb.Length;
}
else
{
charactersFitted = text.Length;
}

return charactersFitted;
}

private Size MeasureString(string text)
{
if (this.measureBlock == null)
{
this.measureBlock = this.GetTextBlock();
}

this.measureBlock.Text = text;
return new Size(measureBlock.ActualWidth, measureBlock.ActualHeight);
}

private int GetMaxTextSize()
{
// Get average char size
Size size = this.MeasureText(" ");
// Get number of char that fit in the line
int charLineCount = (int)(this.Width / size.Width);
// Get line count
int lineCount = (int)(2048 / size.Height);

return charLineCount * lineCount / 2;
}

private int GetMaxLineCount()
{
Size size = this.MeasureText(" ");
// Get number of char that fit in the line
int charLineCount = (int)(this.Width / size.Width);
// Get line count
int lineCount = (int)(2048 / size.Height) - 5;

return lineCount;
}

private TextBlock GetTextBlock()
{
TextBlock textBlock = new TextBlock();
textBlock.TextWrapping = TextWrapping.Wrap;
textBlock.FontSize = this.FontSize;
textBlock.FontFamily = this.FontFamily;
// textBlock.FontStyle = this.FontStyle;
textBlock.FontWeight = this.FontWeight;
textBlock.Foreground = this.Foreground;
textBlock.Margin = new Thickness(0, 0, MeasureText(" ").Width, 0);
return textBlock;
}

private Size MeasureText(string value)
{
TextBlock textBlock = this.GetTextBlockOnly();
textBlock.Text = value;
return new Size(textBlock.ActualWidth, textBlock.ActualHeight);
}

private TextBlock GetTextBlockOnly()
{
TextBlock textBlock = new TextBlock();
textBlock.TextWrapping = TextWrapping.Wrap;
textBlock.FontSize = this.FontSize;
textBlock.FontFamily = this.FontFamily;
textBlock.FontWeight = this.FontWeight;
return textBlock;
}

}
}

个人感觉，分页算法还是有改进空间的，尽可能减少控件数目，并且以后可以考虑实现动态加载，应该可以解决加载速度问题。

这里抛砖引玉了。