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：

[csharp]
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。 

摘自 lanwilliam的专栏