【移动应用开发技术】android怎么实现多线程断点续传功能

【移动应用开发技术】android怎么实现多线程断点续传功能

这篇文章主要介绍了android怎么实现多线程断点续传功能，具有一定借鉴价值，感兴趣的朋友可以参考下，希望大家阅读完这篇文章之后大有收获，下面让在下带着大家一起了解一下。具体内容如下布局:<?xml

version="1.0"

encoding="utf-8"?>

<RelativeLayout

xmlns:android="/apk/res/android"

xmlns:tools="/tools"

android:id="@+id/activity_main"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:paddingBottom="@dimen/activity_vertical_margin"

android:paddingLeft="@dimen/activity_horizontal_margin"

android:paddingRight="@dimen/activity_horizontal_margin"

android:paddingTop="@dimen/activity_vertical_margin">

<TextView

android:text="下载进度"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentTop="true"

android:layout_alignParentLeft="true"

android:layout_alignParentStart="true"

android:layout_marginTop="15dp"

android:id="@+id/tv_progress"

/>

<Button

android:text="下载"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_below="@+id/firstBar"

android:layout_alignParentLeft="true"

android:layout_alignParentStart="true"

android:layout_marginTop="29dp"

android:id="@+id/bt"

/>

<Button

android:text="暂停"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignTop="@+id/bt"

android:layout_toRightOf="@+id/bt"

android:layout_toEndOf="@+id/bt"

android:layout_marginLeft="15dp"

android:layout_marginStart="15dp"

android:id="@+id/bt_pause"

/>

<Button

android:text="继续"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignBottom="@+id/bt_pause"

android:layout_toRightOf="@+id/bt_pause"

android:layout_toEndOf="@+id/bt_pause"

android:layout_marginLeft="18dp"

android:layout_marginStart="18dp"

android:id="@+id/bt_start"

/>

<ProgressBar

android:id="@+id/firstBar"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:layout_below="@+id/tv_progress"

android:layout_alignParentLeft="true"

android:layout_alignParentStart="true"

android:layout_marginTop="21dp"

/>

</RelativeLayout>MainActivity:import

android.os.Bundle;

import

android.os.Environment;

import

android.support.v7.app.AppCompatActivity;

import

android.view.View;

import

android.widget.Button;

import

android.widget.ProgressBar;

import

android.widget.TextView;

import

android.widget.Toast;

import

butterknife.BindView;

import

butterknife.ButterKnife;

import

butterknife.OnClick;

public

class

MainActivity

extends

AppCompatActivity

{

@BindView(R.id.firstBar)

ProgressBar

firstBar;

@BindView(R.id.tv_progress)

TextView

tvprogress;

@BindView(R.id.bt)

Button

bt;

@BindView(R.id.bt_pause)

Button

btPause;

@BindView(R.id.bt_start)

Button

btStart;

//下载地址

private

String

loadUrl

=

".au/pub/TED-talks/911Mothers_2010W-480p.mp4";

//文件缓存路径

private

String

filePath

=

Environment.getExternalStorageDirectory()

+

"/"

+

"911Mothers.mp4";

DownLoadFile

downLoadFile;

@Override

protected

void

onCreate(Bundle

savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

ButterKnife.bind(this);

downLoadFile

=

new

DownLoadFile(this,

loadUrl,

filePath,

3);

downLoadFile.setOnDownLoadListener(new

DownLoadFile.DownLoadListener()

{

@Override

public

void

getProgress(int

progress)

{

tvprogress.setText("当前进度

："

+

progress

+

"

%");

//设置进度条进度

firstBar.setProgress(progress);

if

(progress==100){

Toast.makeText(MainActivity.this,

"下载完成",

Toast.LENGTH_SHORT).show();

}

}

@Override

public

void

onComplete()

{

Toast.makeText(MainActivity.this,

"下载完成",

Toast.LENGTH_SHORT).show();

}

@Override

public

void

onFailure()

{

Toast.makeText(MainActivity.this,

"下载失败",

Toast.LENGTH_SHORT).show();

}

});

}

/*

*

点击事件

*

*/

@OnClick({R.id.bt,

R.id.bt_pause,

R.id.bt_start})

public

void

onViewClicked(View

view)

{

switch

(view.getId())

{

case

R.id.bt:

downLoadFile.downLoad();

break;

case

R.id.bt_pause:

downLoadFile.onPause();

break;

case

R.id.bt_start:

downLoadFile.onStart();

break;

}

}

@Override

protected

void

onDestroy()

{

downLoadFile.onDestroy();

super.onDestroy();

}

}DownLoadFile:import

android.content.Context;

import

android.content.SharedPreferences;

import

android.os.Handler;

import

android.os.Message;

import

java.io.InputStream;

import

java.io.RandomAccessFile;

import

.HttpURLConnection;

import

.URL;

public

class

DownLoadFile

{

private

static

final

String

SP_NAME

=

"download_file";

private

static

final

String

CURR_LENGTH

=

"curr_length";

private

static

final

int

DEFAULT_THREAD_COUNT

=

4;//默认下载线程数

//以下为线程状态

private

static

final

String

DOWNLOAD_INIT

=

"1";

//初始化

private

static

final

String

DOWNLOAD_ING

=

"2";

//正在下载

private

static

final

String

DOWNLOAD_PAUSE

=

"3";

//暂停

private

Context

mContext;

private

String

loadUrl;//网络获取的url

private

String

filePath;//下载到本地的path

private

int

threadCount

=

DEFAULT_THREAD_COUNT;//下载线程数

private

int

fileLength;//文件总大小

//使用volatile防止多线程不安全

private

volatile

int

currLength;//当前总共下载的大小

private

volatile

int

runningThreadCount;//正在运行的线程数

private

Thread[]

mThreads;

private

String

stateDownload

=

DOWNLOAD_INIT;//当前线程状态

//下载进度监听

private

DownLoadListener

mDownLoadListener;

public

void

setOnDownLoadListener(DownLoadListener

mDownLoadListener)

{

this.mDownLoadListener

=

mDownLoadListener;

}

//定义一个下载监听的接口

public

interface

DownLoadListener

{

//返回当前下载进度的百分比

void

getProgress(int

progress);

//下载完成

void

onComplete();

//下载失败

void

onFailure();

}

/*

*

四种有参构造

*

*/

public

DownLoadFile(Context

mContext,

String

loadUrl,

String

filePath)

{

this(mContext,

loadUrl,

filePath,

DEFAULT_THREAD_COUNT,

null);

}

public

DownLoadFile(Context

mContext,

String

loadUrl,

String

filePath,

DownLoadListener

mDownLoadListener)

{

this(mContext,

loadUrl,

filePath,

DEFAULT_THREAD_COUNT,

mDownLoadListener);

}

public

DownLoadFile(Context

mContext,

String

loadUrl,

String

filePath,

int

threadCount)

{

this(mContext,

loadUrl,

filePath,

threadCount,

null);

}

public

DownLoadFile(Context

mContext,

String

loadUrl,

String

filePath,

int

threadCount,

DownLoadListener

mDownLoadListener)

{

this.mContext

=

mContext;

this.loadUrl

=

loadUrl;

this.filePath

=

filePath;

this.threadCount

=

threadCount;

runningThreadCount

=

0;

this.mDownLoadListener

=

mDownLoadListener;

}

/**

*

开始下载

*/

protected

void

downLoad()

{

//在线程中运行，防止anr

new

Thread(new

Runnable()

{

@Override

public

void

run()

{

try

{

//初始化数据

if

(mThreads

==

null)

mThreads

=

new

Thread[threadCount];

//建立连接请求

URL

url

=

new

URL(loadUrl);

HttpURLConnection

conn

=

(HttpURLConnection)

url.openConnection();

conn.setConnectTimeout(5000);

conn.setRequestMethod("GET");

int

code

=

conn.getResponseCode();//获取返回码

if

(code

==

200)

{//请求成功,根据文件大小开始分多线程下载

fileLength

=

conn.getContentLength();

//根据文件大小，先创建一个空文件

//“r“——以只读方式打开。调用结果对象的任何

write

方法都将导致抛出

IOException。

//“rw“——打开以便读取和写入。如果该文件尚不存在，则尝试创建该文件。

//“rws“——

打开以便读取和写入，对于

“rw”，还要求对文件的内容或元数据的每个更新都同步写入到底层存储设备。

//“rwd“——打开以便读取和写入，对于

“rw”，还要求对文件内容的每个更新都同步写入到底层存储设备。

RandomAccessFile

raf

=

new

RandomAccessFile(filePath,

"rwd");

raf.setLength(fileLength);

raf.close();

//计算各个线程下载的数据段

int

blockLength

=

fileLength

/

threadCount;

SharedPreferences

sp

=

mContext.getSharedPreferences(SP_NAME,

Context.MODE_PRIVATE);

//获取上次取消下载的进度，若没有则返回0

currLength

=

sp.getInt(CURR_LENGTH,

0);

for

(int

i

=

0;

i

<

threadCount;

i++)

{

//开始位置，获取上次取消下载的进度，默认返回i*blockLength,即第i个线程开始下载的位置

int

startPosition

=

sp.getInt(SP_NAME

+

(i

+

1),

i

*

blockLength);

//结束位置，-1是为了防止上一个线程和下一个线程重复下载衔接处数据

int

endPosition

=

(i

+

1)

*

blockLength

-

1;

//将最后一个线程结束位置扩大，防止文件下载不完全，大了不影响，小了文件失效

if

((i

+

1)

==

threadCount)

endPosition

=

endPosition

*

2;

mThreads[i]

=

new

DownThread(i

+

1,

startPosition,

endPosition);

mThreads[i].start();

}

}

else

{

handler.sendEmptyMessage(FAILURE);

}

}

catch

(Exception

e)

{

e.printStackTrace();

handler.sendEmptyMessage(FAILURE);

}

}

}).start();

}

/**

*

取消下载

*/

protected

void

cancel()

{

if

(mThreads

!=

null)

{

//若线程处于等待状态，则while循环处于阻塞状态，无法跳出循环，必须先唤醒线程，才能执行取消任务

if

(stateDownload.equals(DOWNLOAD_PAUSE))

onStart();

for

(Thread

dt

:

mThreads)

{

((DownThread)

dt).cancel();

}

}

}

/**

*

暂停下载

*/

protected

void

onPause()

{

if

(mThreads

!=

null)

stateDownload

=

DOWNLOAD_PAUSE;

}

/**

*

继续下载

*/

protected

void

onStart()

{

if

(mThreads

!=

null)

synchronized

(DOWNLOAD_PAUSE)

{

stateDownload

=

DOWNLOAD_ING;

DOWNLOAD_PAUSE.notifyAll();

}

}

protected

void

onDestroy()

{

if

(mThreads

!=

null)

mThreads

=

null;

}

private

class

DownThread

extends

Thread

{

private

boolean

isGoOn

=

true;//是否继续下载

private

int

threadId;

private

int

startPosition;//开始下载点

private

int

endPosition;//结束下载点

private

int

currPosition;//当前线程的下载进度

private

DownThread(int

threadId,

int

startPosition,

int

endPosition)

{

this.threadId

=

threadId;

this.startPosition

=

startPosition;

currPosition

=

startPosition;

this.endPosition

=

endPosition;

runningThreadCount++;

}

@Override

public

void

run()

{

SharedPreferences

sp

=

mContext.getSharedPreferences(SP_NAME,

Context.MODE_PRIVATE);

try

{

URL

url

=

new

URL(loadUrl);

HttpURLConnection

conn

=

(HttpURLConnection)

url.openConnection();

conn.setRequestMethod("GET");

conn.setRequestProperty("Range",

"bytes="

+

startPosition

+

"-"

+

endPosition);

conn.setConnectTimeout(5000);

//若请求头加上Range这个参数，则返回状态码为206，而不是200

if

(conn.getResponseCode()

==

206)

{

InputStream

is

=

conn.getInputStream();

RandomAccessFile

raf

=

new

RandomAccessFile(filePath,

"rwd");

raf.seek(startPosition);//跳到指定位置开始写数据

int

len;

byte[]

buffer

=

new

byte[1024];

while

((len

=

is.read(buffer))

!=

-1)

{

//是否继续下载

if

(!isGoOn)

break;

//回调当前进度

if

(mDownLoadListener

!=

null)

{

currLength

+=

len;

int

progress

=

(int)

((float)

currLength

/

(float)

fileLength

*

100);

handler.sendEmptyMessage(progress);

}

raf.write(buffer,

0,

len);

//写完后将当前指针后移，为取消下载时保存当前进度做准备

currPosition

+=

len;

synchronized

(DOWNLOAD_PAUSE)

{

if

(stateDownload.equals(DOWNLOAD_PAUSE))

{

DOWNLOAD_PAUSE.wait();

}

}

}

is.close();

raf.close();

//线程计数器-1

runningThreadCount--;

//若取消下载