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Android 多线程下载

2011-10-31

package my.Thread;import java.io.BufferedInputStream;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.URL;import java.net.URLConnection;import java.util.con...

package my.Thread;

import java.io.BufferedInputStream;

import java.io.RandomAccessFile;

import java.net.HttpURLConnection;

import java.net.URL;

import java.net.URLConnection;

import java.util.concurrent.CountDownLatch;

import android.app.Activity;

import android.os.Bundle;

import android.os.Environment;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.TextView;

public class ManyThreadActivity extends Activity {

/** Called when the activity is first created. */

private Button button;

private TextView textView;

private static final int THREAD_COUNT = 4;

private CountDownLatch latch = new CountDownLatch(THREAD_COUNT);

private long completeLength = 0;

private long fileLength;

public static String SaveFile=Environment.getExternalStorageDirectory()+"/DownFile/"+"test.Mp3";

public static final String url="http://210.30.12.33:8080/mp3/Beyond.mp3";

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

button=(Button)findViewById(R.id.button1);

textView=(TextView) findViewById(R.id.editText1);

textView.setText(url);

button.setOnClickListener(new MyListener());

}

class MyListener implements OnClickListener{

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

try {

download(url);

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

//进行下载的线程

class DownloadThread extends Thread {

private URL url;

private RandomAccessFile file;

private long from;

private long end;

/**

* @param url 下载的URL

* @param file 下载完成之后存储的文件

* @param from 当前线程对应文件的起始位置

* @param end 当前线程对应文件的结束位置

*/

DownloadThread(URL url, RandomAccessFile file, long from, long end) {

this.url = url;

this.file = file;

this.from = from;

this.end = end;

}

public void run() {

try {

long pos = from;

byte[] buf = new byte[1024*8];

HttpURLConnection cn = (HttpURLConnection) url.openConnection();

//设置请求的起始和结束位置。

cn.setRequestProperty("Range", "bytes=" + from + "-" + end);

BufferedInputStream bis = new BufferedInputStream(cn.getInputStream());

int len;

while ((len = bis.read(buf)) > 0) {

synchronized (file) {

file.seek(pos);

file.write(buf, 0, len);

}

pos += len;

completeLength += len;

System.out.println(completeLength * 100 / fileLength + "%");

}

cn.disconnect();

} catch (Exception e) {

e.printStackTrace();

}

latch.countDown();

}

}

public void download(String address) throws Exception {

URL url = new URL(address);

URLConnection cn = url.openConnection();

fileLength = cn.getContentLength();

long packageLength = fileLength / THREAD_COUNT;//每个线程要下载的字节数

long leftLength = fileLength % THREAD_COUNT;//剩下的字节数

RandomAccessFile file = new RandomAccessFile(SaveFile, "rw");

System.out.println(fileLength);

//计算每个线程请求的起始位置和结束位置。

/*

* 第一个线程的起始位置是0~0+packageLength(每个线程要下载的字节数)

* 第二个线程的起始位置是endPos+1(第一个线程的packageLength+1)~endPos+1+packageLength

* 第二个线程的起始位置是.........

*/

long pos = 0;

for (int i = 0; i < THREAD_COUNT; i++) {

long endPos = pos + packageLength;

new DownloadThread(url, file, pos, endPos).start();

if(leftLength > 0) {

endPos++;

leftLength--;

}

pos = endPos;

}

latch.await();

}

}

\

保存为test.mp3文件

\

摘自 伟哥~ YZ

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