【移動應(yīng)用開發(fā)技術(shù)】Android 使用HttpURLConnection 實現(xiàn)多線程下載

【移動應(yīng)用開發(fā)技術(shù)】Android使用HttpURLConnection實現(xiàn)多線程下載

工具類代碼：

package

com.example.xiaocool.multithreadclient;

import

java.io.InputStream;

import

java.io.RandomAccessFile;

import

.HttpURLConnection;

import

.URL;

public

class

DownUtil

{

//

定義下載資源的路徑

private

String

path;

//

指定所下載的文件的保存位置

private

String

targetFile;

//

定義需要使用多少線程下載資源

private

int

threadNum;

//

定義下載的線程對象

private

DownThread[]

threads;

//

定義下載的文件的總大小

private

int

fileSize;

public

DownUtil(String

path,

String

targetFile,

int

threadNum)

{

this.path

=

path;

this.threadNum

=

threadNum;

//

初始化threads數(shù)組

threads

=

new

DownThread[threadNum];

this.targetFile

=

targetFile;

}

public

void

download()

throws

Exception

{

URL

url

=

new

URL(path);

HttpURLConnection

conn

=

(HttpURLConnection)

url.openConnection();

conn.setConnectTimeout(5

*

1000);

conn.setRequestMethod("GET");

conn.setRequestProperty(

"Accept",

"p_w_picpath/gif,

p_w_picpath/jpeg,

p_w_picpath/pjpeg,

p_w_picpath/pjpeg,

"

+

"application/x-shockwave-flash,

application/xaml+xml,

"

+

"application/vnd.ms-xpsdocument,

application/x-ms-xbap,

"

+

"application/x-ms-application,

application/vnd.ms-excel,

"

+

"application/vnd.ms-powerpoint,

application/msword,

*/*");

conn.setRequestProperty("Accept-Language",

"zh-CN");

conn.setRequestProperty("Charset",

"UTF-8");

conn.setRequestProperty("Connection",

"Keep-Alive");

//

得到文件大小

fileSize

=

conn.getContentLength();

conn.disconnect();

int

currentPartSize

=

fileSize

/

threadNum

+

1;

RandomAccessFile

file

=

new

RandomAccessFile(targetFile,

"rw");

//

設(shè)置本地文件的大小

file.setLength(fileSize);

file.close();

for

(int

i

=

0;

i

<

threadNum;

i++)

{

//

計算每條線程的下載的開始位置

int

startPos

=

i

*

currentPartSize;

//

每個線程使用一個RandomAccessFile進行下載

RandomAccessFile

currentPart

=

new

RandomAccessFile(targetFile,

"rw");

//

定位該線程的下載位置

currentPart.seek(startPos);

//

創(chuàng)建下載線程

threads[i]

=

new

DownThread(startPos,

currentPartSize,

currentPart);

//

啟動下載線程

threads[i].start();

}

}

//

獲取下載的完成百分比

public

double

getCompleteRate()

{

//

統(tǒng)計多條線程已經(jīng)下載的總大小

int

sumSize

=

0;

for

(int

i

=

0;

i

<

threadNum;

i++)

{

sumSize

+=

threads[i].length;

}

//

返回已經(jīng)完成的百分比

return

sumSize

*

1.0

/

fileSize;

}

private

class

DownThread

extends

Thread

{

//

當前線程的下載位置

private

int

startPos;

//

定義當前線程負責下載的文件大小

private

int

currentPartSize;

//

當前線程需要下載的文件塊

private

RandomAccessFile

currentPart;

//

定義已經(jīng)該線程已下載的字節(jié)數(shù)

public

int

length;

public

DownThread(int

startPos,

int

currentPartSize,

RandomAccessFile

currentPart)

{

this.startPos

=

startPos;

this.currentPartSize

=

currentPartSize;

this.currentPart

=

currentPart;

}

@Override

public

void

run()

{

try

{

URL

url

=

new

URL(path);

HttpURLConnection

conn

=

(HttpURLConnection)url

.openConnection();

conn.setConnectTimeout(5

*

1000);

conn.setRequestMethod("GET");

conn.setRequestProperty(

"Accept",

"p_w_picpath/gif,

p_w_picpath/jpeg,

p_w_picpath/pjpeg,

p_w_picpath/pjpeg,

"

+

"application/x-shockwave-flash,

application/xaml+xml,

"

+

"application/vnd.ms-xpsdocument,

application/x-ms-xbap,

"

+

"application/x-ms-application,

application/vnd.ms-excel,

"

+

"application/vnd.ms-powerpoint,

application/msword,

*/*");

conn.setRequestProperty("Accept-Language",

"zh-CN");

conn.setRequestProperty("Charset",

"UTF-8");

InputStream

inStream

=

conn.getInputStream();

//

跳過startPos個字節(jié)，表明該線程只下載自己負責哪部分文件。

inStream.skip(this.startPos);

byte[]

buffer

=

new

byte[1024];

int

hasRead

=

0;

//

讀取網(wǎng)絡(luò)數(shù)據(jù)，并寫入本地文件

while

(length

<

currentPartSize

&&

(hasRead

=

inStream.read(buffer))

>

0)

{

currentPart.write(buffer,

0,

hasRead);

//

累計該線程下載的總大小

length

+=

hasRead;

}

currentPart.close();

inStream.close();

}

catch

(Exception

e)

{

e.printStackTrace();

}

}

}

}MainActivity:package

com.example.xiaocool.multithreadclient;

import

android.os.Handler;

import

android.os.Message;

import

android.support.v7.app.ActionBarActivity;

import

android.os.Bundle;

import

android.view.Menu;

import

android.view.MenuItem;

import

android.view.View;

import

android.widget.Button;

import

android.widget.EditText;

import

android.widget.ProgressBar;

import

java.util.Timer;

import

java.util.TimerTask;

public

class

MainActivity

extends

ActionBarActivity

{

EditText

url;

EditText

target;

Button

downBn;

ProgressBar

bar;

DownUtil

downUtil;

private

int

mDownStatus;

@Override

public

void

onCreate(Bundle

savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

url

=

(EditText)

findViewById(R.id.url);

target

=

(EditText)

findViewById(R.id.target);

downBn

=

(Button)

findViewById(R.id.down);

bar

=

(ProgressBar)

findViewById(R.id.bar);

//

創(chuàng)建一個Handler對象

final

Handler

handler

=

new

Handler()

{

@Override

public

void

handleMessage(Message

msg)

{

if

(msg.what

==

0x123)

{

bar.setProgress(mDownStatus);

}

}

};

downBn.setOnClickListener(new

View.OnClickListener()

{

@Override

public

void

onClick(View

v)

{

//

初始化DownUtil對象

最后一個參數(shù)指定線程數(shù)

downUtil

=

new

DownUtil(url.getText().toString(),

target.getText().toString(),

6);

new

Thread()

{

@Override

public

void

run()

{

try

{

//

開始下載

downUtil.download();

}

catch

(Exception

e)

{

e.printStackTrace();

}

//

定義美妙調(diào)度獲取一次系統(tǒng)的完成進度

final

Timer

timer

=

new

Timer();

timer