wx.downloadFile({

                // 示例 url，并非真实存在

                url: pdf_path,

                success(res) {

                    const filePath = res.tempFilePath

                    console.log(filePath)

                    wx.openDocument({

                        filePath,

                        fileType:‘pdf’,

                        success(res) {

                            console.log(‘打开文档成功’)

                        }

                    })

                }

            })

wx.openDocument  用这个打开的文档，我在安卓机里再转发给好友，就打不开了，我看转发出去的没有文件后缀的，这里请优化下，分享出去带文件后缀，好打开文件