// 預(yù)覽文檔
 lookFile(){
  wx.getNetworkType({
   success: function (res) {
    // networkType字段的有效值：
    // wifi/2g/3g/4g/unknown(Android下不常見的網(wǎng)絡(luò)類型)/none(無網(wǎng)絡(luò))
    if (res.networkType == 'wifi') {
     // 從網(wǎng)絡(luò)上下載pdf文檔
     wx.downloadFile({
      url: 'https://pic25.nipic.com/20121205/10197997_003647426000_2.jpg',
      success: function (res) {
       // 下載成功之后進(jìn)行預(yù)覽文檔
       wx.openDocument({
        filePath: res.tempFilePath
       })
      }
     })
    } else {
     wx.showModal({
      title: '提示',
      content: '當(dāng)前為非Wifi環(huán)境，確定下載嗎？',
      confirmText: '確定',
      cancelText: '取消',
      success: function (res) {
       if (res.confirm) {
        console.log('確定操作')
        wx.downloadFile({
         url: 'https://pic25.nipic.com/20121205/10197997_003647426000_2.jpg',
         success: function (res) {
          // 下載成功之后進(jìn)行預(yù)覽文檔
          wx.openDocument({
           filePath: res.tempFilePath
          })
         }
        })
       } else if (res.cancel) {
        console.log('取消操作')
        wx.showToast({
         title:'取消成功'
        })
       }
      }
     })
    }
   }
  })
 }