Silverlight实现星星闪烁动画

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes; 
 
namespace RandEllipseSample
{
  public partial class MainPage : UserControl
  {
    int shapesCount = 500; //图形数组的容量
    //随机大小的上限
    int theMaxW = 1300;
    int theMaxH = 720;
    Random rand = null;
    Storyboard story = null;
    Ellipse[] myShapes = null;
    public MainPage()
    {
      InitializeComponent();
      rand = new Random();
      story = new Storyboard();
      story.Completed += new EventHandler(story_Completed);
      InitShapes();
      InitAnimation();
      //加载完成后马上播放动画
      this.Loaded += new RoutedEventHandler(MainPage_Loaded);
    } 
 
    void MainPage_Loaded(object sender, RoutedEventArgs e)
    {
      story.Begin();
    } 
 
    void story_Completed(object sender, EventArgs e)
    {
      for (int x = 0; x < shapesCount; x++)
      {
        myShapes[x].Margin = new Thickness(Convert.ToDouble(rand.Next(0, theMaxW)), Convert.ToDouble(rand.Next(0, theMaxH)), 0, 0);
      }
      InitAnimation();
    } 
 
    /// <summary>
    /// 初始化形状数组
    /// </summary>
    private void InitShapes()
    {
      myShapes = new Ellipse[shapesCount];
      //实例化所有成员
      for (int n = 0; n < shapesCount; n++)
      {
        myShapes[n] = new Ellipse();
        myShapes[n].Fill = new SolidColorBrush(Colors.Transparent);
        myShapes[n].StrokeThickness = 2d;
        //笔触为线性渐变
        LinearGradientBrush gBrush = new LinearGradientBrush();
        gBrush.StartPoint = new Point(0, 0);
        gBrush.EndPoint = new Point(1, 1);
        gBrush.GradientStops.Add(new GradientStop()
        {
          Color = Colors.Yellow,
          Offset = 0
        });
        gBrush.GradientStops.Add(new GradientStop()
        {
          Color = Colors.Red,
          Offset = 0.25
        });
        gBrush.GradientStops.Add(new GradientStop()
        {
          Color = Colors.White,
          Offset = 0.5
        });
        gBrush.GradientStops.Add(new GradientStop()
        {
          Color = Colors.Blue,
          Offset = 0.75
        });
        myShapes[n].Stroke = gBrush;
        //位置
        myShapes[n].Margin = new Thickness(Convert.ToDouble(rand.Next(0,theMaxW)), Convert.ToDouble(rand.Next(0,theMaxH)), 0, 0);
        //大小
        myShapes[n].Width = 10;
        myShapes[n].Height = 10;
        myShapes[n].HorizontalAlignment = HorizontalAlignment.Left;
        myShapes[n].VerticalAlignment = VerticalAlignment.Top;
        //加入可视化树
        this.LayoutRoot.Children.Add(myShapes[n]);
      }
    } 
 
    /// <summary>
    /// 初始化动画
    /// </summary>
    private void InitAnimation()
    {
      story.Children.Clear();
      for (int i = 0; i < shapesCount; i++)
      {
        int mSecond = rand.Next(0, 5);
        //透明度
        DoubleAnimation opacityAnimate = new DoubleAnimation();
        opacityAnimate.From = 1.0;
        opacityAnimate.To = 0.0;
        Storyboard.SetTarget(opacityAnimate, myShapes[i]);
        Storyboard.SetTargetProperty(opacityAnimate,
          new PropertyPath("Opacity"));
        opacityAnimate.Duration = new Duration(TimeSpan.FromSeconds(mSecond));
        opacityAnimate.RepeatBehavior = RepeatBehavior.Forever; 
 
        //将时间线添加到情节摘要
        story.Children.Add(opacityAnimate);
      }
    }
  }
}