OkHttp初探2：如何使用OkHttp进行下载封装？带进度条？Kotlin+Flow版本。
本文接上一篇博文：OkHttp初探：如何使用OkHttp进行Get或Post请求？Kotlin版本。
文章目录
-
- 通用模块封装
- 下载文件，带进度，一般封装
- 使用flow封装
通用模块封装
这里封装一些通用的代码，先知道一下就可以了。
/**
* 日志打印
*/
fun log(vararg msg: Any?) {
val nowTime = SimpleDateFormat("HH:mm:ss:SSS").format(System.currentTimeMillis())
println("$nowTime [${Thread.currentThread().name}] ${msg.joinToString(" ")}")
}
/**
* 进度通用回调 不使用flow封装的话 使用这个
*/
internal typealias ProgressBlock = (state: DownloadState) -> Unit
/**
* 下载状态机
*/
sealed class DownloadState {
/**
* 未开始
*/
object UnStart : DownloadState()
/**
* 下载中
*/
class Progress(var totalNum: Long, var current: Long) : DownloadState()
/**
* 下载完成
*/
class Complete(val file: File?) : DownloadState()
/**
* 下载失败
*/
class Failure(val e: Throwable?) : DownloadState()
/**
* 下载失败
*/
class FileExistsNoDownload(val file: File?) : DownloadState()
}
下载文件，带进度，一般封装
fun downloadFile(url: String, destFileDirName: String, progressBlock: ProgressBlock) {
//下载状态 默认未开始
var state: DownloadState = DownloadState.UnStart
progressBlock(state)
// TODO: 2021/12/27 file 创建与判断可以封装
/**
* file 创建判断 可以封装
*/
val file = File(destFileDirName)
val parentFile = file.parentFile
if (!parentFile.exists()) {
parentFile.mkdirs()
}
if (file.exists()) {
//文件存在 不需要下载
state = DownloadState.FileExistsNoDownload(file)
progressBlock(state)
return
} else {
file.createNewFile()
}
//下载
val okHttpClient = OkHttpClient()
val request = Request.Builder().url(url).build()
okHttpClient.newCall(request).enqueue(object : Callback {
override fun onFailure(call: Call, e: IOException) {
state = DownloadState.Failure(e)
progressBlock(state)
}
override fun onResponse(call: Call, response: Response) {
response.use { res ->
//完整长度
var totalLength = 0L
//写入字节
val bytes = ByteArray(2048)
val fileOutputStream = FileOutputStream(file)
res.body?.also { responseBody ->
totalLength = responseBody.contentLength()
}?.byteStream()?.let { inputStream ->
try {
var currentProgress = 0L
var len = 0
state = DownloadState.Progress(totalLength, currentProgress)
do {
if (len != 0) {
currentProgress += len
fileOutputStream.write(bytes,0,len)
}
//状态改变
(state as DownloadState.Progress).current = currentProgress
progressBlock(state)
len = inputStream.read(bytes, 0, bytes.size)
} while (len != -1)
//状态改变完成
state = DownloadState.Complete(file)
progressBlock(state)
} catch (e: Exception) {
state = DownloadState.Failure(e)
progressBlock(state)
} finally {
inputStream.close()
fileOutputStream.close()
}
}
}
}
})
}
使用
downloadFile(
"https://dldir1.qq.com/weixin/Windows/WeChatSetup.exe",
"download/WeChatSetup.exe"
) { state: DownloadState ->
when (val s = state) {
is DownloadState.Complete -> log("下载完成 文件路径为 ${s.file?.absoluteFile}")
is DownloadState.Failure -> log("下载失败 ${s.e?.message}")
is DownloadState.FileExistsNoDownload -> log("已经存在 ${s.file?.absoluteFile}")
is DownloadState.Progress -> log("下载中 ${(s.current.toFloat() / s.totalNum) * 100}%")
DownloadState.UnStart -> log("下载未开始")
}
}
使用flow封装
对于上述封装使用起来没有问题，但是如果在android上面要把进度显示出来的话，就需要手动切换到UI线程了。不太方便。既然都用kotlin了，那么为什么不解除协程Flow封装呢？
所以，下面基于Flow的封装就来了。直接切换到Main线程，美滋滋。
知识储备：
Kotlin：Flow 全面详细指南，附带源码解析。
Flow : callbackFlow使用心得，避免踩坑！
/**
* 使用Flow改造文件下载
* callbackFlow 可以保证线程的安全 底层是channel
*/
fun downloadFileUseFlow(url: String, destFileDirName: String) = callbackFlow<DownloadState> {
var state: DownloadState = DownloadState.UnStart
send(state)
//获取文件对象
val file = File(destFileDirName).also { file ->
val parentFile = file.parentFile
if (!parentFile.exists()) {
parentFile.mkdirs()
}
if (file.exists()) {
state = DownloadState.FileExistsNoDownload(file)
send(state)
//流关闭，返回
close()
return@callbackFlow
} else {
file.createNewFile()
}
}
//下载
val okHttpClient = OkHttpClient().newBuilder()
.dispatcher(dispatcher)
.writeTimeout(30, TimeUnit.MINUTES)
.readTimeout(30, TimeUnit.MINUTES)
.build()
val request = Request.Builder()
.url(url)
.build()
okHttpClient.newCall(request).enqueue(object : Callback {
override fun onFailure(call: Call, e: IOException) {
//更新状态
state = DownloadState.Failure(e)
this@callbackFlow.trySendBlocking(state)
close()
}
override fun onResponse(call: Call, response: Response) {
//下载
val body = response.body
if (response.isSuccessful && body != null) {
//完整长度
val totalNum: Long = body.contentLength()
//当前下载的长度
var currentProgress: Long = 0L
var len = 0
response.use {
//等效于 FileOutputStream(file) 输出流
val outputStream = file.outputStream()
//输入流
val byteStream = body.byteStream()
try {
val bates = ByteArray(2048)
//设置状态对象拉出来，避免循环一直创建对象
state = DownloadState.Progress(totalNum, currentProgress)
//循环读写
do {
if (len != 0) {
currentProgress += len
outputStream.write(bates,0,len)
}
//更新进度
(state as DownloadState.Progress).current = currentProgress
this@callbackFlow.trySendBlocking(state)
len = byteStream.read(bates, 0, bates.size)
} while (len != -1)
//下载完成
state = DownloadState.Complete(file)
this@callbackFlow.trySendBlocking(state)
} catch (e: Exception) {
state = DownloadState.Failure(e)
this@callbackFlow.trySendBlocking(state)
} finally {
outputStream.close()
byteStream.close()
//关闭callbackFlow
this@callbackFlow.close()
}
}
} else {
//更新状态且关闭
state = DownloadState.Failure(Exception(response.message))
this@callbackFlow.trySendBlocking(state)
close()
}
}
})
//使用channelFlow 必须使用awaitClose 挂起flow等待channel结束
awaitClose {
log("callbackFlow关闭 .")
}
}
.buffer(Channel.CONFLATED) //设置 立即使用最新值 buffer里面会调用到fuse函数，继而调用到create函数重新创建channelFlow
.flowOn(Dispatchers.Default) //直接设置callbackFlow执行在异步线程
.catch { e ->
//异常捕获重新发射
emit(DownloadState.Failure(e))
}
使用
//这里使用runBlocking只是为了跑程序，一般和lifecycleScope等合作使用
runBlocking(Dispatchers.Main) {
downloadFileUseFlow(
"https://dldir1.qq.com/weixin/Windows/WeChatSetup.exe",
"download/WeChatSetup.exe"
).onEach { downloadState ->
when (downloadState) {
is DownloadState.Complete -> log("下载完成 文件路径为 ${downloadState.file?.absoluteFile}")
is DownloadState.Failure -> log("下载失败 ${downloadState.e?.message}")
is DownloadState.FileExistsNoDownload -> log("已经存在 ${downloadState.file?.absoluteFile}")
is DownloadState.Progress -> log("下载中 ${(downloadState.current.toFloat() / downloadState.totalNum) * 100}%")
DownloadState.UnStart -> log("下载未开始")
}
}.launchIn(this)
.join()
}
以上就是博主提供的两种简单的封装方式了。
后面会陆续推出OkHttp高阶使用，以及OkHttp源码分析博客。觉得不错关注博主哈~
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