废话不多说，直接看效果：
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no" />
<style type="text/css">
* {
margin: 0;
padding: 0;
}
html,
body {
width: 100vw;
height: 100vh;
overflow: hidden;
}
.canvas {
position: fixed;
top: 0px;
left: 0px;
right: 0px;
background: #fff;
}
.btns {
position: fixed;
bottom: 0px;
left: 0px;
right: 0px;
display: flex;
}
.btns button {
border: none;
flex: 1;
line-height: 40px;
font-size: 18px;
background: #ccc;
outline: none;
}
.btns button:nth-child(2n) {
background: #f1f1f1;
}
</style>
</head>
<body>
<canvas id="canvas" class="canvas"></canvas>
<div class="btns">
<button onclick="btn_clearRect()">清除</button>
</div>
<script>
/** 侦听touchstart事件 **/
//document.body.addEventListener('touchstart', function() {
// event.preventDefault(); //手指滑动时，浏览器会上下左右翻屏
//});
var oCanvas = document.getElementById("canvas");
oCanvas.width = document.body.clientWidth;
oCanvas.height = document.body.clientHeight - 44;
var cxt = oCanvas.getContext("2d");
cxt.lineWidth = 2;
var posX = 0; //x坐标
var posY = 0; //y坐标
var position = null;
//手指触摸屏幕可记录此时的位置作为起点
oCanvas.addEventListener("touchstart", function() {
posX = event.changedTouches[0].clientX;
posY = event.changedTouches[0].clientY;
cxt.moveTo(posX, posY);
});
//手指屏滑动画线
oCanvas.addEventListener("touchmove", function() {
posX = event.changedTouches[0].clientX;
posY = event.changedTouches[0].clientY;
cxt.lineTo(posX, posY);
cxt.stroke();
});
//清空画布
var btn_clearRect = function() {
oCanvas.width = oCanvas.width;
}
</script>
</body>
</html>
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