HTML触摸正方形变色,javascript – 使用触摸事件在HTML5画布上绘制一个正方形

我有一个问题,我试图在画布上使用触摸事件绘制一个正方形并且它不起作用,有人可以帮我找出原因吗？

到目前为止,这是我的代码：

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();

}

HTML5：

Rectangle

再次感谢,

Wardenclyffe