速度向量之单轴速度

源码

// 获取到舞台
var canvas=document.getElementById("stage");
// 舞台2d绘图接口
var context=canvas.getContext("2d");
// 获取中心点置
var centerX=canvas.width/2;
var centerY=canvas.height/2;
// 在舞台上画一条马路
context.lineWidth = 2;
context.strokeStyle = "#ff0000";
context.beginPath();
context.moveTo(0,centerY+2);
context.lineTo(centerX*2,centerY+2);
                 context.stroke();
                 context.closePath();
                  /* *
                  * 向量对象
                   */
                  var Vector2d= function(x,y)
                 {
this.x=x;
this.y=y;
                 } 
                  /* *
                  * 球对象
                   */
                  var Ball= function(x,y,radius,color)
                 {
// 球的中心点位置
this.x=x;
this.y=y;
// 球的半径
this.radius=radius;
// 球的颜色
this.color=color;
// 球的边框颜色
context.strokeStyle = color;
// 球体颜色
context.fillStyle=color; 
/* *
      * 绘制球
       */ 
this.draw= function()
{
context.beginPath(); 
                         context.arc( this.x,  this.y,  this.radius, 0, 2 * Math.PI,  false); 
                         context.fill(); 
                         context.stroke();
                         context.closePath();
}
                 } 
                  // 球的半径 
                  var rd=20;
                  // 创建一个球对象,让球在马路的最左边
                  var ball= new Ball(rd+1,centerY-rd-1,rd,"#ccc"); 
                  // 显示球
                 ball.draw(); 
var ballVector= null;
                  /* *
                  * 开始按钮事件
                   */
                  function Run()
                 { 
                       // 球运行的速度
                       ballVector= new Vector2d(2,0); 
                                     } 

  // 动画
                      var drawAsync = eval(Jscex.compile("async",  function () {
                                  while( true)
                                 {
                 if(ballVector!= null)
{
// 清空马路上方的区域
      context.clearRect(0,0, centerX*2, centerY);
       // 球向右边行始
                                      ball.x+=ballVector.x;
                                       if(ball.x-rd>=centerX*2)
                                      {
ball.x=rd+1;
                                      }
                                      ball.draw();
}
                                      $await(Jscex.Async.sleep(1000/60));
                                  } 
                     }));
                     drawAsync().start();

 作者：Louja

出处：http://loujady.cnblogs.com
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此声明，且在文章页面给出原文连接，否则保留追究法律责任的权利。