Question

我目前正在学习如何使用Canvas，但我目前仍然试图将一个函数放在一个类中。

<script>
var c = document.getElementById("c");
var ctx = c.getContext("2d");

var disc = function(x,y,h,w,c1,c2,ctx){
  this.x=x;
  this.y=y;
  this.h=h;
  this.w=w;
  this.c1=c1;
  this.c2=c2;
  this.ctx=ctx;

}

disc.prototype.draw = function() {
  this.ctx.fillStyle=this.c1;
  this.ctx.fillRect(this.x,this.y,this.w,this.h/2);
  this.ctx.fillStyle=this.c2;
  this.ctx.fillRect(this.x,this.y+this.h/2,this.w,this.h/2);
}

disc.prototype.erase = function() {
  this.ctx.clearRect(this.x,this.y,this.w,this.h);
}


d1 = new disc(100,100,20,40,"#ff0000","#0000ff",ctx);

 var dx=1;
 var dy=1;

 function animate() {
      d1.erase();
      d1.x = d1.x + dx;
      d1.y = d1.y + dy;
      if ( d1.x>=500 || d1.x < 50)  { dx = dx * -1; d1.y = 40;}
      d1.draw();

  }

setInterval(animate,1);


</script>

如何在光盘功能本身内移动动画功能？我已经尝试将其插入光盘功能：

  var dx=1;
  var dy=1;
  animate = function() {
      this.erase();
      this.x = this.x + dx;
      this.y = this.y + dy;
      if ( this.x>=500 || this.x < 50)  { dx = dx * -1; this.y = 40;}
      this.draw();
   }
 this.animate = animate;

以及改变

setInterval(d1.animate,1);

但它给了我

caught TypeError: Object [object Window] has no method 'erase'

Answer 1

您需要将此功能添加到prototype的{{1}}，如下所示：

disc

函数内部的函数？

1 个答案: