onShow: function () {
 var that = this;
 //1. 请求后端API生成小程序码
 that.getQr();

 //2. canvas绘制文字和图片
 const ctx = wx.createCanvasContext('myCanvas');
 var imgPath = '../../../image/intro.png'
 var bgImgPath = '../../../image/bgImgPath.png';
 ctx.drawImage(imgPath, 0, 0, 600, 520);

 ctx.setFillStyle('white')
 ctx.fillRect(0, 520, 600, 280);

 ctx.drawImage(imgPath, 30, 550, 60, 60);
 ctx.drawImage(bgImgPath, 30, 550, 60, 60);
 ctx.drawImage(imgPath, 410, 610, 160, 160);

 ctx.setFontSize(28)
 ctx.setFillStyle('#6F6F6F')
 ctx.fillText('妖妖灵', 110, 590)

 ctx.setFontSize(30)
 ctx.setFillStyle('#111111')
 ctx.fillText('宠友们快来围观萌宠靓照', 30, 660)
 ctx.fillText('我在萌爪幼稚园', 30, 700)

 ctx.setFontSize(24)
 ctx.fillText('长按扫码查看详情', 30, 770)
 ctx.draw()
 },
 // 3. canvas画布转成图片
 wx.canvasToTempFilePath({
 x: 0,
 y: 0,
 width: 600,
 height: 800,
 destWidth: 600,
 destHeight:800,
 canvasId: 'myCanvas',
 success: function(res) {
 console.log(res.tempFilePath);
 that.setData({
  shareImgSrc : res.tempFilePath
 })

 },
 fail:function (res) {
 console.log(res)
 }
 })
 //4. 当用户点击分享到朋友圈时，将图片保存到相册
 wx.saveImageToPhotosAlbum({
 filePath:that.data.shareImgSrc,
 success(res) {
 wx.showModal({
  title: '存图成功',
  content: '图片成功保存到相册了，去发圈噻~',
  showCancel:false,
  confirmText:'好哒',
  confirmColor:'#72B9C3',
  success: function(res) {
  if (res.confirm) {
  console.log('用户点击确定');
  }
  that.hideShareImg()
  }
 })
 }
})