javascript - html5 问题中 Canvas 上的事件监听器

Question

我是 html5 的新手，我想在我的鼠标上创建一个事件监听器，我已经编写了以下代码，但无法理解你，我无法在我的 Canvas 元素上创建事件监听器，请帮助

     var canvasDiv = document.getElementById('canvas');
     canvas_simple = document.createElement('canvas');
     canvas_simple.setAttribute('height', canvasHeight);
     canvas_simple.setAttribute('id', 'canvasSimple');
     canvasDiv.appendChild(canvas_simple);
     if(typeof G_vmlCanvasManager != 'undefined')
     {
     canvas_simple = G_vmlCanvasManager.initElement(canvas_simple);
     }
     context_simple = canvas_simple.getContext("2d");
    context_simple.addEventListener('mousemove', ev_mousemove, false);

根据答案，我也想给我事件监听器代码，可能它也有错误

  var started = false;
  function ev_mousemove (ev) {
  var x, y;

   if (ev.layerX || ev.layerX == 0) { // Firefox
  x = ev.layerX;
  y = ev.layerY;
  } 
  else if (ev.offsetX || ev.offsetX == 0) { // Opera
  x = ev.offsetX;
  y = ev.offsetY;
  }
  if (!started) {

  context.beginPath();
  context.moveTo(x, y);
  started = true;
  }
  else {
    context.strokeStyle = "#df4b26";
    context.lineJoin = "round";
    context.lineWidth = 10;
    context.lineTo(x, y);
    context.stroke();
     }

Answer 1

您想将事件添加到 Canvas ，而不是 2d 上下文:

canvas_simple.addEventListener('mousemove', ev_mousemove, false);

这是一个演示:jsFiddle link