HttpConnection方式访问网络

package com.example.multithreaddownload;

import java.util.Timer;
import java.util.TimerTask;

//import org.crazyit.net.R;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;

@SuppressLint("HandlerLeak")
public class MultiThreadDown extends Activity {
    
    EditText target;
    EditText url;
    Button downButton;
    ProgressBar bar;
    DownUtil downUtil;
    private int mDownloadStatus;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        url = (EditText) findViewById(R.id.url);
        target = (EditText) findViewById(R.id.target);
        downButton = (Button) findViewById(R.id.down);
        bar = (ProgressBar) findViewById(R.id.bar);
        
        final Handler handler = new Handler(){
            
            public void handleMessage(Message msg)
            {
                if(msg.what == 0x123)
                {
                    bar.setProgress(mDownloadStatus);
                }
            }
        };
        
        downButton.setOnClickListener(new OnClickListener()
        {

            @Override
            public void onClick(View v) {
                // 
                
                downUtil = new DownUtil(url.getText().toString(), 
                        target.getText().toString(),5);
                try{
                    downUtil.download();
                }catch(Exception e)
                {
                    e.printStackTrace();
                }
                //设置定时器
                final Timer timer = new Timer();
                timer.schedule(new TimerTask()
                {

                    @Override
                    public void run() {
                        // 
                        double completeRate = downUtil.getCompleteRate();
                        mDownloadStatus = (int) (completeRate * 100);
                        handler.sendEmptyMessage(0x123);
                        if(mDownloadStatus >= 100)
                        {
                            timer.cancel();
                        }
                    }
                    
                
                }, 0, 100);
            }
            
        });
    }

    

}

package com.example.multithreaddownload;

import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;

public class DownUtil {
    
    private String path;
    private String targetFile;
    private int threadNum;
    private DownloadThread[] threads;    
    private int fileSize;

    public DownUtil(String path, String targetFile, int threadNum) {
        super();
        this.path = path;
        this.targetFile = targetFile;
        //初始化thread数组
        threads = new DownloadThread[threadNum];            
        this.threadNum = threadNum;
    }
    
    public void download() throws Exception
    {
        URL url = new URL(path);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();//开启http链接
        connection.setRequestMethod("GET");//向服务器发送GET请求获取数据
        connection.setConnectTimeout(5000);//设置连接超时为5s
//        connection.setRequestProperty(
//                "Accept",
//                "image/gif, image/jpeg, image/pjpeg, image/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, */*");
//        connection.setRequestProperty("Accept-Language", "zh-CN");
//        connection.setRequestProperty("Charset", "UTF-8");
//        connection.setRequestProperty(
//                "User-Agent",
//                "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)");
//        connection.setRequestProperty("Connection", "Keep-Alive");
            
    
        
        fileSize = connection.getContentLength();//获取文件大小
        connection.disconnect();//关闭http连接
        int currentPartSize = fileSize / threadNum +1;//按线程数分割后文件块的大小
        RandomAccessFile file = new RandomAccessFile(targetFile, "rw");//随机产生本地目标文件
        
        file.setLength(fileSize);//根据fileSize设置本地文件大小
        file.close();//关闭文件
        for(int i = 0; i < threadNum; i++)        
        {
            //计算每条线程下载的开始位置
            int startPos = i * currentPartSize;
            //每个线程使用一个RandomAccessFile进行下载
            RandomAccessFile currentPart = new RandomAccessFile(targetFile, "rw");
            //定位该线程的下载位置
            currentPart.seek(startPos);
            //创建下载线程
            threads[i] = new DownloadThread(startPos, currentPartSize,
                    currentPart);
            threads[i].start();
        }
    }
    
    // 获取下载的完成百分比
    public double getCompleteRate()
    {
        // 统计多条线程已经下载的总大小
        int sumSize = 0;
        for (int i = 0; i < threadNum; i++)
        {
            sumSize += threads[i].length;
        }
        // 返回已经完成的百分比
        return sumSize * 1.0 / fileSize;
    }
    private class DownloadThread extends Thread{
        //当前线程下载的位置
        private int startPos;
        //定义当前线程负责下载的文件大小
        private int currentPartSize;
        //定义当前线程负责的下载块
        private RandomAccessFile currentPart;    
        //定义该线程已下载的字节数
        public int length;

        public DownloadThread(int startPos, int currentPartSize,
                RandomAccessFile currentPart) {
//            super();
            this.startPos = startPos;
            this.currentPartSize = currentPartSize;
            this.currentPart = currentPart;
        }

        @Override
        public void run() {    
            super.run();
            try{            
                URL url = new URL(path);
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                connection.setRequestMethod("GET");
                connection.setConnectTimeout(5000);
//                connection.setReadTimeout(5000);
//                connection.setRequestProperty(
//                        "Accept",
//                        "image/gif, image/jpeg, image/pjpeg, image/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, */*");
//                connection.setRequestProperty("Accept-Language", "zh-CN");
//                connection.setRequestProperty("Charset", "UTF-8");
                
                InputStream in = connection.getInputStream();
                //跳过startPos个字节，只下载本线程负责的文件块
                in.skip(this.startPos);
                byte[] buffer = new byte[1024];
                int hasRead = 0;
                while((length < currentPartSize) && (hasRead = in.read(buffer)) != -1)
                {
                    currentPart.write(buffer, 0, hasRead);
                    length += hasRead;
            
                }
                currentPart.close();
                in.close();            
                                
            }catch(Exception e)
            {
                e.printStackTrace();
            }
        }
        
        
        
        
    }
    
    
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    android:text="要下载的资源的URL："
    />
<EditText
    android:id="@+id/url"  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    android:text="http://www.crazyit.org/attachment.php?aid=1093&amp;k=4ec76aeaa41ee84acf667b420e926783&amp;t=1297311085"
    />
<TextView
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    android:text="目标文件："
    />
<EditText
    android:id="@+id/target"  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    android:text="/mnt/sdcard/a.rar"
    />    
<Button
    android:id="@+id/down"  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    android:text="@string/down"
    />
<!-- 定义一个水平进度条,用于显示下载进度 -->
<ProgressBar
    android:id="@+id/bar"
     android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    android:max="100"
    style="@android:style/Widget.ProgressBar.Horizontal"
    />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="down">下载</string>
<string name="app_name">多线程下载</string>
<string name="action_settings">Settings</string>
</resources>

<!-- 在SD卡中创建与删除文件权限 -->
    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
    <!-- 向SD卡写入数据权限 -->
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <!-- 授权访问网络 -->
    <uses-permission android:name="android.permission.INTERNET"/>