Retrofit+协程 文件下载

这种方法太过复杂，建议使用另一种封装方法：

https://blog.csdn.net/jingzz1/article/details/108324102 

//Service的写法
interface UrlService {
    @Streaming
    @GET
    suspend fun downloadFile(@Url url:String): Response<ResponseBody>
}


//开启协程并下载，为了方便调用，下载方法我封装成DSL,参考DowloadBuild
 lifecycleScope.launch() {
    val response = RetrofitUtils.create()
        .downloadFile("文件下载地址")
    dowload(response){
        success { uri ->  
            //下载成功 uri:下载文件的uri
            //uri转file,可以参考：https://blog.csdn.net/jingzz1/article/details/106188462
        }
        error {throwable ->
            //下载失败
        }
        process { downloadedSize, length, process ->
            //下载进度
            //downloadedSize:已下载的大小
            //length:文件总大小
            //process:下载进度

        }
        //设置文件名，如果不设置，会自动获取
        //setFileName = {"xxxxx.后缀"}

        //为了兼容android10,如果需要把文件下载到共享文件夹，可以调用serUri
        /* setUri = {
             if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                 val values = ContentValues().apply {
                     put(MediaStore.MediaColumns.DISPLAY_NAME,"xxxx.后缀") //文件名
                     put(MediaStore.MediaColumns.MIME_TYPE, response.body()?.contentType().toString()) //文件类型
                     put(MediaStore.MediaColumns.RELATIVE_PATH,Environment.DIRECTORY_DOWNLOADS) //共享文件夹，固定写法
                 }
                 context.contentResolver.insert(MediaStore.Downloads.EXTERNAL_CONTENT_URI, values)
             } else
                 Uri.fromFile(File(context.getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS)?.absolutePath+File.separator+"xxxxx.后缀"))
         }*/

    }.startDowload() //调用.startDowload()开启下载

}

 

DowloadBuild代码：

import android.content.Context
import android.net.Uri
import android.os.Environment
import android.webkit.MimeTypeMap
import com.blankj.utilcode.util.LogUtils
import com.blankj.utilcode.util.Utils
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.flow.flow
import kotlinx.coroutines.flow.flowOn
import kotlinx.coroutines.withContext
import okhttp3.ResponseBody
import retrofit2.Response
import java.io.BufferedInputStream
import java.io.File
import java.io.FileOutputStream

/**
 * Created by jingzz on 2020/7/9.
 */
typealias DOWLOAD_ERROR = (Throwable) -> Unit
typealias DOWLOAD_PROCESS = (downloadedSize: Long, length: Long, process: Float) -> Unit
typealias DOWLOAD_SUCCESS = (uri: Uri) -> Unit

suspend fun dowload(response: Response<ResponseBody>,block:DowloadBuild.()->Unit):DowloadBuild{
    val build = DowloadBuild(response)
    build.block()
    return build
}

class DowloadBuild(val response: Response<ResponseBody>) {
    private var error: DOWLOAD_ERROR = {} //错误贺词
    private var process: DOWLOAD_PROCESS = { downloadedSize, filsLength, process -> } //进度
    private var success: DOWLOAD_SUCCESS = {} //下载完成
    private val context: Context = Application.context //全局context
    var setUri: () -> Uri? = { null } //设置下载的uri
    var setFileName: () -> String? = { null } //设置文件名

    fun process(process: DOWLOAD_PROCESS) {
        this.process = process
    }

    fun error(error: DOWLOAD_ERROR) {
        this.error = error
    }

    fun success(success: DOWLOAD_SUCCESS) {
        this.success = success
    }

    suspend fun startDowload() {

        withContext(Dispatchers.Main){
            //使用流获取下载进度
            flow.flowOn(Dispatchers.IO)
                .collect {
                    when(it){
                        is DowloadStatus.DowloadErron -> error(it.t)
                        is DowloadStatus.DowloadProcess -> process(it.currentLength,it.length,it.process)
                        is DowloadStatus.DowloadSuccess -> success(it.uri)
                    }
                }
        }
    }
    val flow = flow<DowloadStatus> {
        try {
            val body = response.body() ?: throw RuntimeException("下载出错")
            //文件总长度
            val length = body.contentLength()
            //文件minetype
            val contentType = body.contentType()?.toString()
            val ios = body.byteStream()
            var uri: Uri? = null
            var file: File? = null
            val ops = kotlin.run {
                setUri()?.let {
                    //url转OutPutStream
                    uri = it
                    context.contentResolver.openOutputStream(it)
                } ?: kotlin.run {
                    val fileName = setFileName() ?: kotlin.run {
                        //如果连文件名都不给，那就自己生成文件名
                        "${System.currentTimeMillis()}.${MimeTypeMap.getSingleton()
                            .getExtensionFromMimeType(contentType)}"
                    }
                    file =
                        File("${context.getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS)}${File.separator}$fileName")
                    FileOutputStream(file)
                }
            }
            //下载的长度
            var currentLength: Int = 0
            //写入文件
            val bufferSize = 1024 * 8
            val buffer = ByteArray(bufferSize)
            val bufferedInputStream = BufferedInputStream(ios, bufferSize)
            var readLength: Int = 0
            while (bufferedInputStream.read(buffer, 0, bufferSize)
                    .also { readLength = it } != -1
            ) {
                ops.write(buffer, 0, readLength)
                currentLength += readLength
                emit(DowloadStatus.DowloadProcess(currentLength.toLong(),length,currentLength.toFloat() / length.toFloat()))
            }
            bufferedInputStream.close()
            ops.close()
            ios.close()
            if (uri != null) {
                emit(DowloadStatus.DowloadSuccess(uri!!))
            } else if (file != null) {
                emit(DowloadStatus.DowloadSuccess(Uri.fromFile(file)))
            }

        } catch (e: Exception) {
            emit(DowloadStatus.DowloadErron(e))
        }
    }



}

sealed class DowloadStatus{
    class DowloadProcess(val currentLength:Long,val length:Long,val process:Float):DowloadStatus()
    class DowloadErron(val t:Throwable):DowloadStatus()
    class DowloadSuccess(val uri:Uri):DowloadStatus()
}