HTML5 canvas在桌面浏览器上工作正常，但在Android上工作不正常

Question

I'm trying to make a canvas that the user can draw on, following this tutorial .

Code as follows:

<canvas id="playSpace" width="500" height="300"></canvas>

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script>
context=document.getElementById('playSpace').getContext("2d");

$('#playSpace').mousedown(function(e){
    var mouseX=e.pageX - this.offsetLeft;
    var mouseY=e.pageY - this.offsetTop;

    paint=true;
    addClick(e.pageX - this.offsetLeft,e.pageY-this.offsetTop);
    redraw();
});

$('#playSpace').mousemove(function(e){
    if(paint){
        addClick(e.pageX - this.offsetLeft,e.pageY - this.offsetTop, true);
        redraw();
    }
});

$('#playSpace').mouseup(function(e){
    paint=false;
});

$('#playSpace').mouseleave(function(e){
    paint=false;
});

var clickX=new Array();
var clickY=new Array();
var clickDrag=new Array();
var paint;

function addClick(x,y,dragging)
{
    clickX.push(x);
    clickY.push(y);
    clickDrag.push(dragging);
}

function redraw(){
    context.clearRect(0,0,context.canvas.width,context.canvas.height);

    context.strokeStyle="#df4b26";
    context.lineJoin="round";
    context.lineWidth=5;

    for(var i=0;i<clickX.length;i++){
        context.beginPath();
        if(clickDrag[i] && i){
            context.moveTo(clickX[i-1],clickY[i-1]);
        }
        else{
            context.moveTo(clickX[i]-1,clickY[i]);
        }
        context.lineTo(clickX[i],clickY[i]);
        context.closePath();
        context.stroke();
    }
}

</script>

I tested it in this JSFiddle and it works fine on Chrome on my desktop: clicking and dragging draws red lines.

But when I open the same JSFiddle in Chrome on my Android phone, running Android 4.2.2, nothing happens: I drag my finger across the canvas but no lines appear.

Do I need to do something different to enable dragging in Android?

Answer 1

A mobile device does not necessarily have mouse move events, it has touch events.

Take a look at this answer:

How to get continuous mousemove event when using android mobile browser?

Answer 2

Try using this for android

  e.touches[0].pageX 
  e.touches[0].pageY