Android 多线程下载

最新推荐文章于 2025-09-05 16:34:31 发布

fulianwu

最新推荐文章于 2025-09-05 16:34:31 发布

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分类专栏： Android 文章标签： android import thread exception url button

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转自：http://blog.youkuaiyun.com/rwyz1314/article/details/6919596

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();
}
}