Javascript ES6 HTML5画布图像未绘制到背景画布或背景画布未显示

Question

Images are not drawing to bg_canvas with a z-index of 0, only my main game canvas overlay is showing, i have only included the start of the code.

// HTML

<canvas id="bg-canvas" width="768" height="600"></canvas>
<canvas id="canvas" width="768" height="600"></canvas>

// CSS

canvas {
    position: absolute;
    top: 0;
    left: 0;
}

#canvas {   
z-index: 1

}

#bg-canvas {
    z-index: 0
}


// Javascript
const bg_canvas = document.getElementById('bg-canvas');
const bg_ctx = bg_canvas.getContext("2d");
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");

const map = {
    object: {
        brickwall: new Image(),
        woodenbox: new Image()
    }
};

map.object.brickwall.src = "objects/brickwall.jpeg";
map.object.woodenbox.src = "objects/boximage.jpg";



ctx.clearRect(0,0,canvas.width,canvas.height);
bg_ctx.clearRect(0,0,bg_canvas.width,bg_canvas.height);


// var currentItemEquipped;
// drawImage(imgsrc, xcoord, ycoord, sizex, sizey) // drawImage parameters



map.object.brickwall.onload = () => bg_ctx.drawImage(map.object.brickwall, 100, 100, 100, 100);
map.object.woodenbox.onload = () => bg_ctx.drawImage(map.object.woodenbox, 200, 200, 100, 100);

The player is drawing and the rest of the code is working completely fine however, i am not able to draw these images to the canvas, it may be a problem with z-indexes or that the overlaying canvas is not transparent.

Answer 1

Have you tried "window.addEventListener" ?

Because sometimes i got the same issue in some browsers...

try this:

 function LoadImages(){ bg_ctx.drawImage(map.object.brickwall, 100, 100, 100, 100); bg_ctx.drawImage(map.object.woodenbox, 200, 200, 100, 100); } window.addEventListener("load", LoadImages); 

Answer 2

不得不在draw方法中调用该函数，但是由于背景画布从未被清除，所以不确定为什么。