使用触摸事件在HTML5画布上绘制一个正方形

Question

I have a problem, I'm trying to draw a square on the canvas with the use of touch event and it not working, can someone help me figure out why?

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Here's my code so far:

JAVASCRIPT:

// "Draw Rectangle" Button
function rect(){
var canvas = document.getElementById('canvasSignature'), ctx = canvas.getContext('2d'), rect = {}, drag = false;

function init() {
  canvas.addEventListener("touchstart", touchHandler, false);
  canvas.addEventListener("touchmove", touchHandler, false);
  canvas.addEventListener("touchend", touchHandler, false);
}


function touchHandler(event) {
  if (event.targetTouches.length == 1) { //one finger touche
    var touch = event.targetTouches[0];

    if (event.type == "touchstart") {
      rect.startX = touch.pageX;
      rect.startY = touch.pageY;
      drag = true;
    } else if (event.type == "touchmove") {
      if (drag) {
        rect.w = touch.pageX - rect.startX;
        rect.h = touch.pageY - rect.startY ;
        draw();
      }
    } else if (event.type == "touchend" || event.type == "touchcancel") {
      drag = false;
    }
  }
}

function draw() {
  ctx.fillRect(rect.startX, rect.startY, rect.w, rect.h);
}

init();
}

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HTML5:

      <div id="canvasDiv">
    <canvas id="canvasSignature" width="580px" height="788px" style="border:2px solid #000; background: #FFF;"></canvas>
</div>



<div id="rect">  
    <p><button onclick="rect();">Rectangle</button></p>
</div>  

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Thanks again, Wardenclyffe

Answer 1

Tested in Chrome with emulated touch events works with this jsFiddle The problem seems to be the way you bind your click event. I just used jQuery.

Or without jQuery: just a plain addEventListener