WeChat applet implements countdown to call the camera's automatic photo taking function

<!--index.wxml-->

 <view class="userinfo-login">
 <view class="page-body">
  <view class="page-body-wrapper">
  <view wx:if="{{src}}"></view> 
  <!-- 如果存在已经拍好的照片就不再显示调用摄像头的组件-->
  <view wx:else>
   <camera device-position="back" flash="off" binderror="error" style="width: 100%; height: 200px;"></camera>
  <!-- 调用摄像头的组件-->
</view>
  <image wx:if="{{src}}" mode="widthFix" src="{{src}}"></image>
  <!-- 显示拍好的照片-->
  </view>
 </view>
 </view>

//index.js

const app = getApp()
Page({
 data: {
 userInfo: {},
 counting: false//倒计时
 },
 onLoad: function () {
 this.daojishi();//一进来就拍照倒计时
 this.ctx = wx.createCameraContext()//创建摄像头对象
 },
 //倒计时
 daojishi: function () {
 var that = this;
 if (!that.data.counting) {
  //开始倒计时5秒
  countDown(that, 5);
 }
 }
})
//倒计时函数 在page外

function countDown(that, count) {
 if (count == 0) {
 //等于0时拍照 
 that.ctx.takePhoto({
  quality: 'high',
  success: (res) => {
  that.setData({
   src: res.tempImagePath
  })
  wx.showToast({
   title: '拍照完成',
  })
  }
 })
 that.setData({
  counting: false
 })
 return;
 }
 wx.showLoading({//加载时显示倒计时
 title: '拍照倒计时'+count+'秒',
 })

 setTimeout(function () {
 wx.hideLoading()
 }, 1000)
 that.setData({
 counting: true,
 })
 setTimeout(function () {
 count--;
 countDown(that, count);
 }, 1000);
}