HTML<view class='vw'>    <canvas canvas-id='myCanvas' style='width:375px;height:667px;background:#f5f5f5;'>    </canvas>    <button class='btn' bindtap='abc'>    保存圖片    </button></view>javascriptonReady: function (e) {    //這是canvas將圖片放在canvas上    var ctx = wx.createCanvasContext('myCanvas')    var imgPath = 'http://up.qqjia.com/z/23/tu27726_2.jpg'    var bgImgPath = 'http://img.keaiq.com/d/file/15155477475202100.jpg'    var smallage = 'https://t2.38mt.com/tempx/11/11767/3762-73772.jpg'    ctx.setFillStyle('#ffffff')    ctx.fillRect(0,520,600,280)    ctx.drawImage(imgPath, 100, 120,180,260)    ctx.drawImage(smallage, 220, 320,60,60)    ctx.drawImage(bgImgPath, 30,520,80,100)    ctx.setFillStyle('#6f6f6f')    ctx.font = "18px Arial";    ctx.fillText('歪歪歪', 110,580)    ctx.draw()    setTimeout(() => {      this.canvasImg()    }, 700)  }//轉(zhuǎn)換 canvasImg: function () {   console.log(123)   var that = this   // 畫(huà)布轉(zhuǎn)成圖片   wx.canvasToTempFilePath({     canvasId: 'myCanvas',     x: 0,     y: 0,     width: 375,     height: 667,     //生成圖片的大小     destWidth: 375,     destHeight: 667,     success: function (res) {       wx.hideLoading()       console.log(res.tempFilePath, 'canvas畫(huà)圖片呀')       that.setData({         img: res.tempFilePath       })     }   }) }然后到手機(jī)上面會(huì)是全部空白的，存電腦上還能顯示，但是還帶著按鈕 存手機(jī)上就是空白的