<template>
<view >
<view class="title">請在下面輸入簽名：</view>
<canvas class="mycanvas" canvas-id="mycanvas" @touchstart="touchstart" @touchmove="touchmove" @touchend="touchend"></canvas>
<view class="footer">
<view class="left" @click="finish">完成</view>
<view class="right" @click="clear">清除</view>
</view>
</view>
</template>

<script>
var x = 20;
var y =20;
export default{
data(){
return {
ctx:'',         //繪圖圖像
points:[]       //路徑點集合 
}
},
onLoad() {
this.ctx = uni.createCanvasContext("mycanvas",this);   //創(chuàng)建繪圖對象

//設置畫筆樣式
this.ctx.lineWidth = 4;
this.ctx.lineCap = "round"
this.ctx.lineJoin = "round"
},
methods:{
//觸摸開始，獲取到起點
touchstart:function(e){
let startX = e.changedTouches[0].x;
let startY = e.changedTouches[0].y;
let startPoint = {X:startX,Y:startY};

/* **************************************************
#由于uni對canvas的實現有所不同，這里需要把起點存起來
 * **************************************************/
this.points.push(startPoint);

//每次觸摸開始，開啟新的路徑
this.ctx.beginPath();
},

//觸摸移動，獲取到路徑點
touchmove:function(e){
let moveX = e.changedTouches[0].x;
let moveY = e.changedTouches[0].y;
let movePoint = {X:moveX,Y:moveY};
this.points.push(movePoint);       //存點
let len = this.points.length;
if(len>=2){
this.draw();                   //繪制路徑
}

},

// 觸摸結束，將未繪制的點清空防止對后續(xù)路徑產生干擾
touchend:function(){                   
this.points=[];
},

/* ***********************************************
#   繪制筆跡
#1.為保證筆跡實時顯示，必須在移動的同時繪制筆跡
#2.為保證筆跡連續(xù)，每次從路徑集合中區(qū)兩個點作為起點（moveTo）和終點(lineTo)
#3.將上一次的終點作為下一次繪制的起點（即清除第一個點）
************************************************ */
draw: function() {
let point1 = this.points[0]
let point2 = this.points[1]
this.points.shift()
this.ctx.moveTo(point1.X, point1.Y)
this.ctx.lineTo(point2.X, point2.Y)
this.ctx.stroke()
this.ctx.draw(true)
},

//清空畫布
clear:function(){
let that = this;
uni.getSystemInfo({
success: function(res) {
let canvasw = res.windowWidth;
let canvash = res.windowHeight;
that.ctx.clearRect(0, 0, canvasw, canvash);
that.ctx.draw(true);
},
})
},

//完成繪畫并保存到本地
finish:function(){
uni.canvasToTempFilePath({
  canvasId: 'mycanvas',
  success: function(res) {
    let path = res.tempFilePath;
uni.saveImageToPhotosAlbum({
filePath:path
})
  } 
})
}
},
}
</script>

<style>
.title{
height:50upx;
line-height: 50upx;
font-size: 16px;
}
.mycanvas{
width: 100%;
height: calc(100vh - 200upx);
background-color: #ECECEC;
}
.footer{
font-size: 16px;
height: 150upx;
display: flex;
justify-content: space-around;
align-items: center;
}
.left,.right{
line-height: 100upx;
height: 100upx;
width: 250upx;
text-align: center;
font-weight: bold;
color: white;
border-radius: 5upx;
}
.left{
background: #007AFF;
}
.right{
background:orange;
}
</style>