Kotlin协程+Retrofit下载文件并实现进度监听

Kotlin协程+Retrofit下载文件并实现进度监听

1.前言

网上很多Retrofit+RxJava下载文件的功能，这里我使用kotlin+协程的方式使用一下，并且结合workmanager使用下载

  DownloadWorker.startDownload(
                this@MainActivity,
                "https://dldir1.qq.com/wework/work_weixin/wxwork_android_3.0.31.13637_100001.apk",
                this@MainActivity.cacheDir.path,
                "wxwork_android_3.apk"
            )

2. 实现过程

1. 构建下载的ApiService

import okhttp3.ResponseBody
import retrofit2.http.GET
import retrofit2.http.Streaming
import retrofit2.http.Url

interface ApiService {
   
   
 	@Streaming
 	@GET
 	suspend fun downloadFile(@Url fileUrl: String?): ResponseBody
 }

2. 声明相关监听方法

typealias download_error = suspend (Throwable) -> Unit
typealias download_process = suspend (downloadedSize: Long, length: Long, progress: Float) -> Unit
typealias download_success = suspend (uri: File) -> Unit

3. 构建Retrofit,并且获取ApiService

import retrofit2.Retrofit

object HttpKit {
   
   
    val retrofit = Retrofit.Builder()
        .baseUrl("http://www.xxx.com")
        .validateEagerly(true) //在开始的时候直接开始检测所有的方法
        .build()

    val apiService = retrofit.create(ApiService::class.java)
}				

4. 定义返回实体

/**
 * @author stj
 * @Date 2021/10/28-16:42
 * @Email 375105540@qq.com
 */

class HttpResult<out T> constructor(val value: Any?) {
   
   

    val isSuccess: Boolean get() = value !is Failure && value !is Progress

    val isFailure: Boolean get() = value is Failure

    val isLoading : Boolean get() = value is Progress

    fun exceptionOrNull(): Throwable? =
        when (value) {
   
   
            is Failure -> value.exception
            else -> null
        }
    /*
    .....代码省略
    */

    companion object {
   
   
        fun <T> success(value: T): HttpResult<T> =
            HttpResult(value)

        fun <T> failure(exception: Throwable): HttpResult<T> =
            HttpResult(createFailure(exception))

        fun <T> progress(currentLength: Long, length: Long, process: Float):HttpResult<T> =
            HttpResult(createLoading(currentLength, length, process))
    }

    data class Failure(val exception: Throwable)

    data class Progress(val currentLength: Long, val length: