wxml

<view class="header">
  <text>头像</text>
  <button class="butt" plain="true" open-type="chooseAvatar" bind:chooseavatar="chooseAvatar">
    <image src="{{HeadUrl}}" mode="" style="width: 70px;height: 70px;margin-top: 20px;" />
  </button>
</view>

js

javascript">page({
  data: {
    HeadUrl: 'https://pic.imgdb.cn/item/64367f2c0d2dde5777557749.png' //默认头像(登录前)

  },
// 头像
  chooseAvatar(e) {
    const {
      avatarUrl
    } = e.detail
    console.log(avatarUrl); //本地图片
    wx.uploadFile({
      url: 'https://travel.kuxia.top/api/science/upload',
      filePath: avatarUrl,
      name: 'file',
      success: (res) => {
        var data = JSON.parse(res.data);
        console.log('https://travel.kuxia.top' + data.front_file); //服务器图片
        this.setData({
          HeadUrl: 'https://travel.kuxia.top' + data.front_file,
          // HeadUrl: data.front_file
        })
        wx.showToast({
          title: '上传成功',
          icon: 'success',
          duration: 2000 //持续的时间
        })
      },
      fail: (err) => {
        console.log(err);
      }
    })
  },
})

效果：