在画布上获取鼠标点击事件

Question

我一直在尝试并尝试使用我的简单javascript脚本将弹跳球移动到鼠标点击事件发生的位置.我在这里有脚本.它将与id的任何大小的任何画布对接game.球反弹但忽略鼠标点击.你知道什么是错的吗？谢谢.

var canvas;
var x, y;
var dx=4;
var dy=4;
var d = 20;
var width, height;

function init() {
    canvasE = document.getElementById('game');
    canvas= canvasE.getContext('2d');
    width = canvasE.width;
    height = canvasE.height;
    x = d+dx+1;
    y = d+dy+1;
    canvasE.addEventListener("click", onClick, false);

    clear();

    canvas.beginPath();
    canvas.fillStyle="#0000ff";
    // Draws a circle of radius 20 at the coordinates 100,100 on the canvas
    canvas.arc(x-1,y-1,d,0,Math.PI*2,true);
    canvas.closePath();
    canvas.fill();
    setInterval(loop, 15);
}

function loop() {
    clear();

    canvas.beginPath();
    canvas.fillStyle="#0000ff";
    // Draws a circle of radius 20 at the coordinates 100,100 on the canvas
    canvas.arc(x,y,d,0,Math.PI*2,true);
    canvas.closePath();
    canvas.fill();
    // Boundary Logic
    if( x<(d-dx)+1 || x>width-(d+dx)-1) dx=-dx;
    if( y<(d-dx)+1 || y>height-(d+dy)-1) dy=-dy;
    x+=dx;
    y+=dy;
}
function clear() {
    canvas.fillStyle="#ffffff";
    canvas.fillRect(0,0,width,height);
    canvas.fillStyle="#888888";
    canvas.strokeRect(0,0,width,height);
}

function onClick(e) {
    var clickX;
    var clickY;
    if (e.pageX || e.pageY) { 
        clickX = e.pageX;
        clickY = e.pageY;
    }
    else { 
        clickX = e.clientX + document.body.scrollLeft + document.documentElement.scrollLeft; 
        clickY = e.clientY + document.body.scrollTop + document.documentElement.scrollTop; 
    } 
    clickX -= gCanvasElement.offsetLeft;
    clickY -= gCanvasElement.offsetTop;
    x = clickX;
    y = clickY;
}

Answer 1

这里有更合适的(虽然不是100%防弹)点击代码:

http://jsfiddle.net/4Lanc/

作为旁注,如果您与其他画布程序员一起工作,分别使用"canvasE和canvas"而不是"canvas和context/ctx"作为命名约定可能会产生一些严重的混淆.我强烈建议转到"canvas and context/ctx".