Android 文件分段上传和下载实现方案

randomaccessfile

       private val default_block_size: long = 50 * 1024 * 1024 //50mb
        val blocksize=default_block_size
        val randomaccessfile = randomaccessfile(filepath, "r")
        val filelen = randomaccessfile.length()
        //超过设定的单个文件大小,需要分块上传
            val blockfilenum = math.ceil((filelen / blocksize.todouble())).toint()
            xlogutil.d("${tag}blockfilenum:$blockfilenum,,,,filelen:$filelen,,,blocksize:$blocksize,,,requestid:$requestid")
            var offset = 0l
            var successnum = 0
            var issendresult = true
            for (i in 0 until blockfilenum) {
                val startoffset = i * blocksize
                val blockfilelen = math.min(blocksize, filelen - startoffset)
                val filedata = getfiledata(filepath, offset, blockfilelen.toint())
                // 创建文件名请求体
                val requestbody = requestbody.create(null, filedata)
                val call = retrofitclient.getuploadfileservice(
                    token,
                    requestid,
                    offset.tostring(),
                    uploadtype
                ).uploadfile(file.name, requestbody)
                xlogutil.d("${tag}upload 第${i + 1}块 block file,offset:$offset,,,blockfilelen:$blockfilelen,,,blockfilenum:$blockfilenum,,,filelen:$filelen,,,filepath:$filepath,,,filedata size:${filedata?.size},,,requestid:$requestid")
                offset += blockfilelen
                call.enqueue(object : callback<responsebody?> {
                    override fun onresponse(
                        call: call<responsebody?>,
                        response: response<responsebody?>
                    ) {
                        val code = response.code()
                        xlogutil.d("${tag}upload 第${i + 1}块 block file result code:$code,,,requestid:$requestid")
                        if (code == 201) {
                            //处理成功响应
                            successnum++
                            if (successnum == blockfilenum) {
                                xlogutil.d("${tag}upload all block file success,blockfilenum:$blockfilenum,,,requestid:$requestid")
                                listener?.apply {
                                    onsuccess(constant.success, requestid)
                                }
                                //上传完
                            }
                        } else {
                            //处理失败响应
                        }
                    }
                    override fun onfailure(call: call<responsebody?>, t: throwable) {
                        // 处理请求失败
                        xlogutil.d("${tag}upload 第${i + 1}块 block file onfailure message:${t.printstacktrace()}")
                    }
                })
            }
    /**
     * 根据偏移量获取分块文件数据
     */
    fun getfiledata(filepath: string, offset: long, length: int): bytearray? {
        // 使用randomaccessfile随机访问文件
        var randomaccessfile: randomaccessfile? = null
        try {
            randomaccessfile = randomaccessfile(filepath, "r")
            val filechannel = randomaccessfile.channel
            // 将文件的部分区域映射为内存区域
            val mappedbytebuffer =
                filechannel.map(filechannel.mapmode.read_only, offset, length.tolong())
            val data = bytearray(length)
            // 从映射区域中读取数据
            mappedbytebuffer[data]
            return data
        } catch (e: exception) {
            e.printstacktrace()
            return null
        } finally {
            if (randomaccessfile != null) {
                try {
                    randomaccessfile.close()
                } catch (e: exception) {
                    e.printstacktrace()
                }
            }
        }
    }

                val folder = file(download_folder_path)
                            if (!folder.exists()) {
                                folder.mkdirs()
                            }
                            val filename = getfilenamewithpath(filepath)
                            val downfile = file(download_folder_path + file.separator + filename)
                            if (!downfile.exists()) {
                                downfile.createnewfile()
                            }
                            // 使用输入流保存响应体到文件,这里通常是通过http请求，返回的文件流，替换即可
                            val inputstream = body.bytestream()
                            val rw = randomaccessfile(downfile, "rw")
                            rw.seek(startposition)//文件写入的初始位置
                            var hasreads = 0
                            var readlenght: long = 0
                            val bytes = bytearray(4096)
                            while ((inputstream.read(bytes).also { hasreads = it }) > 0) {
                                rw.write(bytes, 0, hasreads)
                                readlenght += hasreads
                                // val l = (readlenght * 100 / contentlength) as int 单块文件写入进度
                            }
                            // 关闭文件输出流和输入流
                            inputstream.close()
                            rw.close()
    /**
     * 根据文件路径获取文件名
     */
    fun getfilenamewithpath(path: string): string {
        if (textutils.isempty(path)) {
            return ""
        }
        val start = path.lastindexof("/")
        return if (start != -1) {
            path.substring(start + 1)
        } else {
            "default_name"
        }
    }