uniapp实现微信小程序的电子签名效果(附demo)

画布可以做很多事情，比如可以绘图，也可以做海报。在这里只是想拿它来的实现亲笔签名，开启不一样的亲笔签名姿势。

开发框架：uniapp
开发语言：vue2
展示平台：微信小程序（实际可以兼容多个平台）

标签和样式没什么好说的，这里绘制了简单的页面，见下图：

1、标签和样式

<template>
<view class="page-content">
<view class="form">
<view class="form-content">
<canvas class="form-content__canvas" canvas-id="canvas_sign" @touchstart="touchstart"
@touchmove="touchmove" @touchend="touchend" disable-scroll="true"></canvas>
</view>

<view class="form-footer">
<button class="form-footer__reset" @click="autographClick(1)">重置</button>
<button class="form-footer__save" @click="autographClick(2)">保存</button>
<button class="form-footer__preview" @click="autographClick(3)">预览</button>
</view>
</view>

</view>
</template>

<style lang="scss" scoped>
/*
* 横屏后的适配方案
* @param $rpx为需要转换的字号
* @参考 https://blog.csdn.net/sdfsfsdscd/article/details/91375066
**/
@function tovmin($rpx) {
@return #{$rpx * 100 / 750}vmin;
}

.page-content {
width: 100vw;
height: 100vh;

.form {
display: flex;
flex-direction: column;
width: 100％;
height: 100％;

.form-content {
width: 100％;
height: 100％;

&__canvas {
height: calc(100vh - tovmin(20) - tovmin(120) - constant(safe-area-inset-bottom));
height: calc(100vh - tovmin(20) - tovmin(120) - env(safe-area-inset-bottom));
width: 100vw;
}
}

.form-footer {
padding-top: tovmin(20);
height: calc(tovmin(120) + constant(safe-area-inset-bottom));
height: calc(tovmin(120) + env(safe-area-inset-bottom));
width: 100％;

display: flex;
flex-direction: row;

background: #FFFFFF;
box-shadow: 0 tovmin(4) tovmin(20) tovmin(2) rgba(183, 183, 183, 0.20);

button {
width: 20vw;

height: tovmin(88);
line-height: tovmin(88);
border-radius: tovmin(48);
text-align: center;
font-size: tovmin(36);
font-weight: bold;
}

button::after {
border: none;
}

&__reset {
color: #008AFE;
border: tovmin(1) solid #008AFE;
}

&__save {
background-image: linear-gradient(135deg, #1BC5FF 0％, #008AFE 100％);
}

&__preview {
color: #008AFE;
border: tovmin(1) solid #008AFE;
}
}
}
}
</style>

2、横屏切换

到【pages.json】文件中添加横屏切换配置
注意：不同的平台横屏切换将有所不一样。这里是针对微信小程序的横屏适配

{
"pages": [ //pages数组中第一项表示应用启动页，参考：https://uniapp.dcloud.io/collocation/pages
{
"path": "pages/index/index",
"style": {
"navigationBarTitleText": "亲笔签名",//导航栏标题
"pageOrientation": "landscape",//切换横屏
"enablePullDownRefresh": false,//关闭下拉刷新
"disableScroll": true // 整体页面禁止上下滑动
}
}
],
"globalStyle": {
"navigationBarTextStyle": "black",
"navigationBarBackgroundColor": "#FFFFFF",
"backgroundColor": "#f5f5f5",
"navigationStyle": "default", // default/custom。custom即取消默认的原生导航栏
"mp-alipay": {
"transparentTitle": "always",
"titlePenetrate": "YES"
}
}
}

然后是绘制逻辑处理，注意点在代码中备注：

3、绘图

3.1、初始化数据会吧？

data() {
return {
canvasCtx: '', //绘图图像
points: [], //路径点集合
hasSign: false,
isInit: false,
}
},
onLoad(query) {
this.canvasCtx = uni.createCanvasContext('canvas_sign', this) //创建绘图对象
//设置画笔样式
this.canvasCtx.lineWidth = 6
// 设置线条的端点样式
this.canvasCtx.lineCap = 'round'
// 设置线条的交点样式
this.canvasCtx.lineJoin = 'round'
},

3.2、触摸开始时获取起点，会吧？

touchstart: function(e) {
if (!this.isInit) {
this.isInit = true
this.autographClick(1);
}
let startX = e.changedTouches[0].x
let startY = e.changedTouches[0].y
let startPoint = {
X: startX,
Y: startY
}
this.points.push(startPoint)
//每次触摸开始，开启新的路径
this.canvasCtx.beginPath()
},

3.3、触摸移动获取路径点，会吧？

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) //存点
let len = this.points.length
if (len >= 2) {
this.draw() //绘制路径
}

},

3.4、触摸结束，将未绘制的点清空防止对后续路径产生干扰，简单吧？

touchend: function() {
this.points = []
this.canvasCtx.draw(true)
},

3.5、绘制笔迹，没得问题吧？

这里有几个注意点：

1.为保证笔迹实时显示，必须在移动的同时绘制笔迹
2.为保证笔迹连续，每次从路径集合中区两个点作为起点（moveTo）和终点(lineTo)
3.将上一次的终点作为下一次绘制的起点（即清除第一个点）

draw: function() {
let point1 = this.points[0]
let point2 = this.points[1]
this.points.shift()
this.canvasCtx.moveTo(point1.X, point1.Y)
this.canvasCtx.lineTo(point2.X, point2.Y)
this.canvasCtx.stroke()
this.canvasCtx.draw(true)
this.hasSign = true
},

4、扫尾处理

上面的实现了，说明就可以签下你大名了。这里扫尾工作（按钮点击功能实现）只是景上添花。根据实际情况不一定要做。

<script>
export default {
methods: {
// 底部按钮点击操作
autographClick(type) {
let that = this
if (type === 1) {
//清空画布
this.hasSign = false
uni.getSystemInfo({
success: function(res) {
let canvas = uni.createSelectorQuery().select('.form-content__canvas')
canvas.boundingClientRect().exec(function(data) {
console.log('canvas', data)
console.log('canvas wh:' + data[0].width + 'X' + data[0].height)
let canvasw = Math.ceil(data[0].width)
let canvash = Math.ceil(data[0].height)
that.canvasCtx.fillStyle = '#fff'
that.canvasCtx.fillRect(0, 0, canvasw, canvash)
that.canvasCtx.draw(true)
})
}
})

} else {
if (!this.hasSign) {
uni.showToast({
title: '签名不能为空',
icon: 'none',
duration: 2000
})
return
}
uni.getSystemInfo({
success: function(res) {
let canvas = uni.createSelectorQuery().select('.form-content__canvas')
canvas.boundingClientRect().exec(function(data) {
console.log('canvas saveSign:', data[0].width + 'X' + data[0].height)
let canvasw = Math.ceil(data[0].width)
let canvash = Math.ceil(data[0].height)
uni.canvasToTempFilePath({
destWidth: canvasw,
destHeight: canvash,
fileType: 'jpg',
canvasId: 'canvas_sign',
success: function(res) {
console.log('图片导出成功：', res)
let path = res.tempFilePath

// 保存图片
if (type === 2) {
that.uploadPic(path)
} else if (type === 3) {
// 预览图片
uni.previewImage({
urls: [path]
})
}
},
fail: (err) => {
// http://tmp/2LVQyvzddk2R820a9009dff43323d8e7fc9ef7a8d076.jpg
console.log('图片导出失败：', err)
}
})
})
}
})
}
},

// 图片上传处理
uploadPic(tempFile) {
// 1、将本地图片上传到服务器（假装是七牛云服务器）
// 2、将七牛云返回的链接，上传到我们的服务器平台
console.log("------:", tempFile);
uni.showLoading({
title: '正在上传中...'
})
setTimeout(() => {
uni.showToast({
title: '假装签名上传成功',
duration: 2000,
icon: 'none'
});
}, 1000);
}
}
}
</script>

demo地址：

gitee地址：https://gitee.com/chenzm_186/autograph-mini.git

来源：https://blog.csdn.net/weixin_38633659/article/details/124700129