Question

我试图随机选择一个带有值的语句，这些语句从精灵表中的某个点开始绘制。这是我目前的代码。

    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;  
    }

我稍后会绘制它所选择的值。

问题我的绘图主要是所有这些，但同时只绘制一个空白图像，我已经检查了所有X和Y位置，它们都是正确的并且在精灵表中匹配。

以下是我用来绘制精灵的代码：

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

Answer 1

Math.floor(Math.random()*7+1)可以取值1到7.删除+1。

Answer 2

我认为您的绘图代码可能有问题：

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

在一行中：this.srcX+this.width,this.srcY,this.width,this.he‌ight, 您正在将对象宽度添加到源位置。我想这可能会抛弃你的精灵画。请参阅下面的参考评论示例：

// draw image to screen drawImage(imageObject, 
//     sourceX, sourceY, sourceWidth, sourceHeight,
//     destinationX, destinationY, destinationWidth, destinationHeight)
ctx.drawImage(imageObject, 
    this.srcX, this.srcY, this.width, this.height, 
    this.drawX, this.drawY, this.width, this.height);

Javascript html5画布随机切换语句图像

2 个答案: