Javascript html5 canvas 随机 switch 语句图片

Question

我正在尝试随机选择一个语句，其中包含从 sprite 表中的某个点绘制的值。这是我当前的代码。

    this.asteroid = Math.floor(Math.random()*7+1);
    switch(this.asteroid)
    {
    case 0:
        this.srcX = 0;
        this.srcY = 528;
        this.width = 32;
        this.height = 33;
        break;
    case 1:
        this.srcX = 32;
        this.srcY = 528;
        this.width = 32;
        this.height = 33;
        break;  
    case 2:
        this.srcX = 64;
        this.srcY = 528;
        this.width = 32;
        this.height = 33;
        break;
    case 3:
        this.srcX = 63;
        this.srcY = 565;
        this.width = 62;
        this.height = 60;           
        break;
    case 4:
        this.srcX = 125;
        this.srcY = 565;
        this.width = 62;
        this.height = 60;           
        break;
    case 5:
        this.srcX = 187;
        this.srcY = 565;
        this.width = 62;
        this.height = 60;           
        break;
    case 6:
        this.srcX = 0;
        this.srcY = 632;
        this.width = 116;
        this.height = 120;          
        break;  
    }

稍后我将绘制它选择的值。

问题是我绘制了大部分图像，但同时只绘制了一张空白图像，我检查了所有 X 和 Y 位置，它们在 Sprite 表中都是正确且匹配的。

下面是我用来绘制 Sprite 的代码:

this.drawX -= this.speed;
ctxEnemy.drawImage(imgSprite,
    this.srcX+this.width,this.srcY,this.width,this.he‌​ight,
    this.drawX,this.drawY,this.width,this.height);
this.checkEscaped();

Answer 1

Math.floor(Math.random()*7+1) 可以取 1 到 7 之间的值。删除 +1。