[Silverlight 2.0 控制物体绕圆弧运行(C#初探篇)]

 

[Silverlight 2.0 控制物体绕圆弧运行(C#初探篇)] 
           
程序运行时：小地球将绕着圆形轨迹做圆周运动。

【xaml】：很简单，一张图片，再使用一个 Ellipse ，无填充颜色即可，记得为图片起名字 [earth] 
<Canvas Margin="0,0,0,0"> 
  <Ellipse Height="300" Width="300" Canvas.Left="0" Canvas.Top="0" Fill="{x:Null}" 
           Stroke="#FFFFA500" StrokeThickness="3"/> 
  <Image Height="50" Width="50" Canvas.Left="0" Canvas.Top="0" Source="52.png" x:Name="earth"/> 
</Canvas> 
【xaml.cs】记得引用时间控件的命名空间 
using System.Windows.Threading; 
public partial class Page : UserControl 
    { 
        DispatcherTimer timer1 = new DispatcherTimer(); 
        DispatcherTimer timer2 = new DispatcherTimer(); 
    //设置 x 坐标轴变化范围(300 为该圆的直径) 
        double x_temp = 0; 
        double x2_temp = 300; 
        //初始加载事件 
        public Page() 
        { 
            InitializeComponent(); 
            //设置时钟频率为 5 毫秒 
            TimeSpan ts = TimeSpan.FromMilliseconds(0.005); 
            timer1.Interval = ts; 
            timer1.Tick += new EventHandler(timer_Tick); 
            timer1.Start(); 
            timer2.Interval = ts; 
            timer2.Tick += new EventHandler(timer2_Tick); 
        } 
        /// <summary> 
        /// 根据圆弧的 x 坐标获取 y 坐标的方法 
        /// </summary> 
        /// <param name="a">圆弧中心点的 x 坐标</param> 
        /// <param name="b">圆弧中心点的 y 坐标</param> 
        /// <param name="c">圆弧的半径</param> 
        /// <param name="d">x 坐标轴的最大范围</param> 
        /// <returns>返回与 x 坐标相关的圆弧 y 坐标</returns> 
        public double get_y(double a, double b, double c, double d) 
        { 
            double A = a; 
            double B = b; 
            double R = c; 
            double x = d; 
            double y = 0; 
            //分解 (x - a)(x - a) 
            double x_result = (x * x) - (2 * A * x) + (A * A); 
           //变换圆标准方程式 
            for (x = 0; x <= 2 * R;x++ ) 
            { 
                double j = Math.Sqrt(R * R - x_result); 
                y = j + B; 
            } 
            return y; 
        } 
        /// <summary> 
        /// timer2 控制事件 
        /// 该事件处控制一个 圆心为 150，150，半径为 150 的圆弧(下半弧) 
        /// </summary> 
        void timer2_Tick(object sender, EventArgs e) 
        { 
            double y2_temp = this.get_y(150,150,150,x2_temp); 
            earth.SetValue(Canvas.LeftProperty,x2_temp-25); 
            earth.SetValue(Canvas.TopProperty,y2_temp-25); 
            x2_temp--; 
            //当 x 坐标递减到等于 0 时,下半弧完成,重新初始 
            if (x2_temp == 0) 
            { 
                timer2.Stop(); 
                timer1.Start(); 
                x2_temp = 300; 
            } 
        } 
        /// <summary> 
        /// timer1 控制事件 
        /// 该事件处控制一个 圆心为 150，150，半径为 150 的圆弧(上半弧) 
        /// </summary> 
        void timer_Tick(object sender, EventArgs e) 
        { 
            x_temp = x_temp + 1; 
            double y_temp = this.get_y(150, 150, 150, x_temp); 
            //上半弧的纵坐标等于圆弧的直径减去下半弧的纵坐标 
            double y_really = 300 - y_temp; 
            earth.SetValue(Canvas.LeftProperty, x_temp-25); 
            earth.SetValue(Canvas.TopProperty, y_really-25); 
            //当 x 坐标递增到等于圆弧直径长时,上半弧完成,重新初始 
            if (x_temp == 300) 
            { 
                timer1.Stop(); 
                timer2.Start(); 
                x_temp = 0; 
            } 
        } 
    }