Silverlight 背景平鋪——比較簡單的實現方法

         由於blend不夠普及，圖片平鋪問題在所難免。以前寫過如何在WPF中利用VisualBrush進行平鋪。但是在silverlihgt中是沒有VisualBrush的。那隻能通過代碼來控制圖片平鋪用了。

        在google中找了一些實現方法，但總感覺太複雜。比較經典的當然是Elite.Silverlight3.PixelShaders這個項目中的平鋪方法，但是過於複雜，並且不支持絕對的平鋪即需要指明在X軸平鋪數量和在Y軸的平鋪數量。即便是使用寬度除以圖片寬度來計算，也是稍顯麻煩。後來就找到了一個繼承於Panel的TitlePanel，這個是比較簡單的實現方法，切不用修改以往的代碼。貼上代碼以及示例。
        

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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.Windows.Media.Imaging;
using System.Diagnostics;

namespace glPro.Common
{
    public class TilePanel : Panel
    {
        #region DependencyProperty setup
        // Dependency properties for Tile Width, Height and Image
        public static readonly DependencyProperty TileWidthProperty =
            DependencyProperty.Register("TileWidth", typeof(double), typeof(TilePanel),
                  new PropertyMetadata(double.NaN, new PropertyChangedCallback(TileWidthPropertyChanged)));

        public static readonly DependencyProperty TileHeightProperty =
            DependencyProperty.Register("TileHeight", typeof(double), typeof(TilePanel),
                      new PropertyMetadata(double.NaN, new PropertyChangedCallback(TileHeightPropertyChanged)));

        public static readonly DependencyProperty ImageProperty =
            DependencyProperty.Register("Image", typeof(ImageBrush), typeof(TilePanel), new PropertyMetadata(null,
                                                new PropertyChangedCallback(ImagePropertyChanged)));

        public double TileWidth
        {
            get { return (double)GetValue(TileWidthProperty); }
            set { SetValue(TileWidthProperty, value); }
        }

        public double TileHeight
        {
            get { return (double)GetValue(TileHeightProperty); }
            set { SetValue(TileHeightProperty, value); }
        }

        public ImageBrush Image
        {
            get { return (ImageBrush)GetValue(ImageProperty); }
            set { SetValue(ImageProperty, value); }
        }

        #endregion

        private Size _lastFinalSize;
        private ImageBrush _imgBrush;
        private bool _needsUpdate = false;

        public TilePanel()
        {
            this.SizeChanged += new SizeChangedEventHandler(TilePanelSizeChanged);
        }

        /// <summary>
        /// Called when the size of the panel changes.
        /// </summary>
        /// <param name="sender">This panel</param>
        /// <param name="e">The new size information</param>
        protected virtual void TilePanelSizeChanged(object sender, SizeChangedEventArgs e)
        {
            if (e.NewSize != _lastFinalSize)
            {
                _lastFinalSize = e.NewSize;

                // adjust the clipping rectangle based on the new size
                RectangleGeometry rg = new RectangleGeometry();
                rg.Rect = new Rect(new Point(), _lastFinalSize);
                this.Clip = rg;

                TileAdjustmentNeededAsync();
            }            
        }

        /// <summary>
        /// Signal that an adjustment to the tiles is needed,
        /// then makes the call asynchronously.
        /// By asynchronously making this call, it can help prevent
        /// unnecessary work by the panel.
        /// </summary>
        protected void TileAdjustmentNeededAsync()
        {
            // by doing this sync, we can queue up several request
            // but then really only handle the last one.
            _needsUpdate = true;
            // async call the adjust tiles
            this.Dispatcher.BeginInvoke(delegate
            {
                AdjustTiles();
            });
        }
        
        private static void TileHeightPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            TilePanel tilePanel = d as TilePanel;
            if (tilePanel != null)
            {
                Debug.WriteLine("TileHeight Changed: {0}", e.NewValue);
                double val = (double)e.NewValue;
                if ( val == double.NaN || val <= 0.0)
                {
                    throw new ArgumentOutOfRangeException("TileHeight");
                }

                tilePanel.TileAdjustmentNeededAsync();
            }
        }
 
        private static void TileWidthPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            TilePanel tilePanel = d as TilePanel;
            if (tilePanel != null)
            {
                Debug.WriteLine("TileWidth Changed: {0}", e.NewValue);
                double val = (double)e.NewValue;
                if (val == double.NaN || val <= 0.0)
                {
                    throw new ArgumentOutOfRangeException("TileWidth");
                }

                tilePanel.TileAdjustmentNeededAsync();
            }
        }
      
        private static void ImagePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            // put code here to handle the property changed for Image
            TilePanel tilePanel = d as TilePanel;
            if (tilePanel != null )
            {
                Debug.WriteLine("ImagePropertyChanged");
                tilePanel._imgBrush = e.NewValue as ImageBrush;
                // remove all of the existing tiles as they no longer are valid
                tilePanel.Children.Clear();
                tilePanel.TileAdjustmentNeededAsync();
            }
        }
 
        /// <summary>
        /// Perform the standard Arrange. Here though, all of the tiles
        /// are placed based on the tilesize specified.
        /// </summary>
        /// <param name="finalSize">the actual size that the panel has been given</param>
        /// <returns>The size taken (which is always what it was given).</returns>
        protected override Size ArrangeOverride(Size finalSize)
        {
            UIElementCollection children = Children;
            double tw = TileWidth;
            double th = TileHeight;
            double x = 0, y = 0;

            foreach (UIElement uie in Children)
            {
                if (x >= finalSize.Width)
                {
                    x = 0;
                    y += th;
                }

                uie.Arrange(new Rect(x, y, tw, th));
                x += tw;
            }

            return finalSize;
        }

        /// <summary>
        /// Adjusts the quantity of the tiles based on the 
        /// size of the panel and immediately calls
        /// UpdateLayout so the new tiles can be properly 
        /// layed out.
        /// </summary>
        protected virtual void AdjustTiles()
        {
            Debug.WriteLine("AdjustTiles - Update Needed: {0}", _needsUpdate);
            // seems that it was already done ...
            if (!_needsUpdate) { return; }
            _needsUpdate = false;

            // if no image brush is set ... all the children are cleared!
            if (_imgBrush == null) 
            {
                this.Children.Clear();
                return ; 
            }

            double tw = TileWidth;
            double th = TileHeight;

            // determine how many we actually need
            int totalNeededX = (int) Math.Ceiling(this.ActualWidth / tw);
            int totalNeededY = (int) Math.Ceiling(this.ActualHeight / th);
            int totalNeeded = totalNeededX * totalNeededY;

            // there may be too many 
            if (totalNeeded < this.Children.Count)
            {
                while (this.Children.Count > totalNeeded)
                {
                    this.Children.RemoveAt(this.Children.Count - 1);                   
                }
            }
            // or too few ...
            else if (this.Children.Count < totalNeeded)
            {
                while (this.Children.Count < totalNeeded)
                {
                    Rectangle r = new Rectangle();
                    r.Width = tw;
                    r.Height = th;
                    r.Fill = _imgBrush;
                    this.Children.Add(r);                                        
                }
            }

            this.UpdateLayout();
        }
    }
}

在xaml頁面中：引用此類： xmlns:local="clr-namespace:glPro.Common"

    <Grid>
            <local:TilePanel  x:Name="pnlTile"
                              TileWidth="4"
                              TileHeight="61">
                <local:TilePanel.Image>
                    <ImageBrush ImageSource="Images/2-1上平鋪.png" />
                </local:TilePanel.Image>
            </local:TilePanel>
        </Grid>

TileWidth是圖片的寬度，TileHeight是圖片的高度.其他的都是自動計算的。就這麼簡單。貼上找來的源碼。靠，才發現CSDN不能上傳源碼。抱歉！不過基本上代碼拷貝過去就能用。