多线程下载文件（Kotlin版本）
学习Kotlin有一段时间了，但是目前在公司用不上这个，所以打算自己平时写博客的时候多用Kotlin来写Demo。今天是使用Kotlin写了一个多线程下载的demo用来锻炼自己使用Kotlin开发的能力，开始撸代码。
一、效果图
二、撸代码
package com.study.download.morecoroutinedownloaddemo
import android.content.pm.PackageManager
import android.os.AsyncTask
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.os.Environment
import android.util.Log
import android.view.View
import android.widget.Toast
import com.study.download.morecoroutinedownloaddemo.utlis.PermissionCheckUtils
import kotlinx.android.synthetic.main.activity_main.*
import kotlinx.coroutines.experimental.launch
import java.io.File
import java.io.RandomAccessFile
import java.net.HttpURLConnection
import java.net.URL
class MainActivity : AppCompatActivity() {
var path = "http://192.168.31.105:8080/HotSpot/tomcat.avi"
//协程数量
var coroutineCount = 3
var coroutineRunningCount = coroutineCount
//权限数组
var permissionArray = arrayOf(android.Manifest.permission.WRITE_EXTERNAL_STORAGE, android.Manifest.permission.READ_EXTERNAL_STORAGE)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
fun downloadByCoroutine(view: View) {
val size = PermissionCheckUtils.checkActivityPermissions(this, permissionArray, 100, null)
if (size == 0) {
//runBlocking { } 以此种方式启动的协程仍旧运行于main线程中，所以联网操作不可以在此处完成
//用于执行协程任务，通常用于启动最外层的协程
startDownload()
}
}
/**
* 开始下载
*/
private fun startDownload() {
coroutineRunningCount = coroutineCount
pb_1.progress = 0
pb_2.progress = 0
pb_3.progress = 0
AsyncTask.THREAD_POOL_EXECUTOR.execute { }
//协程
// async {
// println("当前async的线程名称为：${Thread.currentThread().name}")
// beforeDownload()
// }
//使用async{}.await()可以返回协程执行的结果
//线程
// Thread {
// beforeDownload()
// }.start()
//线程池
AsyncTask.THREAD_POOL_EXECUTOR.execute {
beforeDownload()
}
}
private fun beforeDownload() {
println("当前线程名称为：${Thread.currentThread().name}")
//创建与文件地址绑定的连接
var url = URL(path)
//打开文件连接对象
val openConnection: HttpURLConnection = url.openConnection() as HttpURLConnection
//设置请求方式
openConnection.requestMethod = "GET"
//设置连接时间
openConnection.connectTimeout = 5000
//获取网络连接的响应码
val responseCode = openConnection.responseCode
//响应码等于200，说明创建连接成功
if (responseCode == 200) {
//获取文件长度
val contentLength = openConnection.contentLength
println("获取到的文件长度为：$contentLength")
//先创建一个跟将要下载文件大小相同的文件
val sdPath = Environment.getExternalStorageDirectory().absolutePath
//使用rw模式可以使用缓冲区，往硬盘中写数据
val filePath = "$sdPath/tomcat.avi"
var file = File(filePath)
if (file.exists()) {
file.delete()
}
var raf = RandomAccessFile(filePath, "rw")
//设置创建文件的大小
raf.setLength(contentLength.toLong())
//这句话执行完成之后将会生成一个tomcat.avi文件，该文件的大小跟上一句赋值的长度一样大
raf.close()
var blockSize = contentLength / coroutineCount
for (i in 0 until coroutineCount) {
//开始下载的文件坐标
var start = i * blockSize
//下载截止的文件坐标
var end = (i + 1) * blockSize - 1
//最后一个线程下载截止的文件坐标
if (i == coroutineCount - 1) {
end = contentLength - 1
}
println("当前协程的id$i,文件下载的起始坐标$start,文件下载的截止坐标$end")
//启动相应协程，实现多协程下载
// downloadByLaunch(start, end, sdPath, i)
downloadByThread(start, end, sdPath, i)
}
}
}
private fun downloadByThread(start: Int, end: Int, sdPath: String?, coroutineId: Int) {
// Thread {
// reallyDownload(start, end, sdPath, coroutineId)
// }.start()
AsyncTask.THREAD_POOL_EXECUTOR.execute {
reallyDownload(start, end, sdPath, coroutineId)
}
}
private fun downloadByLaunch(start: Int, end: Int, sdPath: String?, coroutineId: Int) {
launch {
reallyDownload(start, end, sdPath, coroutineId)
}
}
private fun reallyDownload(start: Int, end: Int, sdPath: String?, coroutineId: Int) {
val name = Thread.currentThread().name
Log.e("thread", name)
//重新创建连接，进行指定位置下载
//创建与文件地址绑定的连接
var url = URL(path)
//打开文件连接对象
val openConnection: HttpURLConnection = url.openConnection() as HttpURLConnection
//设置请求方式
openConnection.requestMethod = "GET"
//设置连接时间
openConnection.connectTimeout = 5000
//在请求头中封装客户端所需要的数据
openConnection.setRequestProperty("range", "bytes=$start-$end")
//获取网络连接的响应码
val responseCode = openConnection.responseCode
//此时返回206的响应码才算是成功的
if (responseCode == 206) {
var inputStream = openConnection.inputStream
//创建文件
var raf = RandomAccessFile("$sdPath/tomcat.avi", "rw")
//跳到指定位置
raf.seek(start.toLong())
var len = -1
//设定缓冲区
var buf = ByteArray(1024)
var flag = true
var progress = 0
while (flag) {
//读取数据，返回下标
len = inputStream.read(buf)
//TODO 可以在此处记录下载文件的坐标，从而实现断点下载
flag = len != -1
//写数据
if (flag) {
raf.write(buf, 0, len)
progress += len
}
when (coroutineId) {
0 -> {
pb_1.max = end - start
pb_1.progress = progress
println("当前正在运行的协程号码是$coroutineId,progress是$progress")
}
1 -> {
pb_2.max = end - start
pb_2.progress = progress
println("当前正在运行的协程号码是$coroutineId,progress是$progress")
}
2 -> {
pb_3.max = end - start
pb_3.progress = progress
println("当前正在运行的协程号码是$coroutineId,progress是$progress")
}
}
}
raf.close()
//同步锁，因为操作的是同一资源，为了避免操作错乱，所以此处的锁必须是唯一锁和同一锁
// synchronized(MainActivity::class) {
// coroutineRunningCount--
// if (coroutineRunningCount == 0) {
// runOnUiThread {
// Toast.makeText(this@MainActivity, "下载完成", Toast.LENGTH_SHORT).show()
// }
// } else {
// println("当前正在运行的协程号码是$coroutineRunningCount")
// }
// }
}
}
override fun onRequestPermissionsResult(requestCode: Int, permissions: Array, grantResults: IntArray) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults)
var flag = true
for (i in grantResults) {
//判断是否赋予权限的标记
flag = if (i == PackageManager.PERMISSION_GRANTED) {
flag && true
} else {
flag && false
}
}
//如果权限赋予成功，那么久开始下载
if (flag) {
startDownload()
}
}
}