我的Javascript贴图不会绘制吗？

Mitch Wardle 发表于 Dev

米奇·沃德尔

这是我的脚本，我似乎无法弄清楚出了什么问题，我想绘制一个12 * 12的瓦片地图，并且瓦片为32px-32px。当我运行页面时，磁贴不会绘制，我尝试使用parse int，如下所示，但仍然无法正常工作。

if(parseInt(mapArray[x][y]) == 0){
    ctx.drawImage(rockTile, posX, posY, tileSize, tileSize);
}

这是我创建的脚本。

var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = (32 * 12);
canvas.height = (32 * 12);
document.body.appendChild(canvas);

var rockTile = new Image();
rockTile.src = "../Images/dc-dngn/floor/rect_gray0.png";
var tileSize = 32;
var posX = 0;
var posY = 0;

var mapArray = [
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
];

$(document).ready(function(){
    drawMap();
});

function drawMap(){
    for(var x = 0; x < mapArray.length; x++){
        for(var y = 0; y < mapArray[x].length; y++){
            if(mapArray[x][y] == 0){
                ctx.drawImage(rockTile, posX, posY, tileSize, tileSize);
            }
            posX += 32;
        }
        posX = 0;
        posY += 32;
    }
}

如果有人可以帮助我绘制我的瓷砖，将不胜感激，谢谢！

实体

您可以看到两个主要问题：

您正在访问document.body它之前定义。
您可能正在使用图像，然后再加载图像。

这是解决这两个问题的代码：

// variables are defined as global variables
var posX = 0;
var posY = 0;
var tileSize = 32;
var mapArray;
var canvas;
var ctx;
var rockTile;

$(function() {
    // document should be defined now
    canvas = document.createElement("canvas");
    ctx = canvas.getContext("2d");
    canvas.width = (32 * 12);
    canvas.height = (32 * 12);
    document.body.appendChild(canvas);

    mapArray = [
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
    ];

    // wait until the image is loaded to draw
    rockTile = new Image();
    rockTile.onload = drawMap;
    rockTile.src = "../Images/dc-dngn/floor/rect_gray0.png";        
});

function drawMap(){
    posX = 0;
    posY = 0;
    for(var x = 0; x < mapArray.length; x++){
        for(var y = 0; y < mapArray[x].length; y++){
            if(mapArray[x][y] == 0){
                ctx.drawImage(rockTile, posX, posY, tileSize, tileSize);
            }
            posX += 32;
        }
        posX = 0;
        posY += 32;
    }
}