Android&多线程下载

package com.zachary.mutildownloader;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.net.URL;
import java.net.URLConnection;

import android.util.Log;

public class FileDownloadThread extends Thread {
    private static final int BUFFER_SIZE = 1024;
    private URL url;
    private File file;
    private int startPosition;
    private int endPosition;
    private int curPosition;
    //用于标示当前线程是否下载完成
    private boolean finished = false;
    private int downloadSize = 0;
    
    final static String TAG = "LOGCAT";
    
    public FileDownloadThread(URL url, File file, int startPosition, int endPosition){
        this.url = url;
        this.file = file;
        this.startPosition = startPosition;
        this.curPosition = startPosition;
        this.endPosition = endPosition;
    }

    @Override
    public void run() {
        // TODO Auto-generated method stub
        BufferedInputStream bis = null;
        RandomAccessFile fos = null;
        byte[] buf = new byte[BUFFER_SIZE];
        URLConnection con = null;
        try {
            con = url.openConnection();
            con.setAllowUserInteraction(true);
            Log.i(TAG, "con.setAllowUserInteraction(true);");
            //设置当前线程下载的起点，终点
            con.setRequestProperty("Range", "bytes=" + startPosition + "-" + endPosition);
            
            //使用java中的RandomAccessFile 对文件进行随机读写操作
            fos = new RandomAccessFile(file, "rw");
            //设置开始写文件的位置  
            fos.seek(startPosition);
            bis = new BufferedInputStream(con.getInputStream());
            //开始循环以流的形式读写文件  
            while(curPosition < endPosition) {
                int len = bis.read(buf, 0, BUFFER_SIZE);
                if(len == -1)
                    break;
                fos.write(buf, 0, len);
                curPosition = curPosition + len;
                if(curPosition > endPosition){
                    downloadSize += len - (curPosition - endPosition) + 1;
                }else {
                    downloadSize += len;
                }
            }
            this.finished = true;
            Log.i(TAG, "the thread was finished");
            bis.close();
            fos.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            Log.d(getName() +" Error:", e.getMessage());  
        }
    }
    
    public boolean isFinished() {
        return finished;
    }
    
    public int getDownloadSize() {
        return downloadSize;
    }
}

package com.zachary.mutildownloader;

import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
    
    private Button downloadBtn = null;
    private ProgressBar downloadProgressBar = null;
    private TextView myTextView = null;
    private int downloadedSize = 0;
    private int fileSize = 0;
    
    final static String TAG = "LOGCAT";
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        downloadBtn = (Button)findViewById(R.id.downloadButton);
        downloadProgressBar = (ProgressBar)findViewById(R.id.downloadBar);
        myTextView = (TextView)findViewById(R.id.myTextView);
        downloadProgressBar.setVisibility(View.VISIBLE);
        downloadProgressBar.setProgress(0);
        
        downloadBtn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                String urlStr = "http://zhangmenshiting.baidu.com/data2/music/35420301/35420301.mp3?xcode=54e756b52270bf9f05efbff149ebffea&mid=0.05505464576834";
                download(urlStr);
            }
            
        });
        
    }
    
    private void download(String urlStr){
        String downloadDir = Environment.getExternalStorageDirectory() + "/myDownload/";
        File file = new File(downloadDir);
        if(!file.exists()){
            file.mkdirs();
            Toast.makeText(MainActivity.this,"make the Dir", Toast.LENGTH_LONG).show();
        }
        String fileName = "abc.mp3";
        downloadBtn.setClickable(false);
        downloadProgressBar.setProgress(0);
        new downloadTask(urlStr, 5, downloadDir + fileName).start();
        Log.i(TAG,"Begin to download");
    }
    
    
    Handler handler = new Handler() {  
        @Override  
        public void handleMessage(Message msg) {  
            //当收到更新视图消息时，计算已完成下载百分比，同时更新进度条信息  
            int progress = (Double.valueOf((downloadedSize * 1.0 / fileSize * 100))).intValue();  
            if (progress == 100) {  
                downloadBtn.setClickable(true);  
                myTextView.setText("下载完成！");  
            } else {  
                myTextView.setText("当前进度:" + progress + "%");  
            }  
            downloadProgressBar.setProgress(progress);  
        }  
   
    };  
    
    //主下载线程 
    public class downloadTask extends Thread{
        private int blockSize, downloadSizeMore;
        private int threadNum = 5;
        String urlStr, threadNo, fileName;
        public downloadTask(String urlStr, int threadNum, String fileName){
            this.urlStr = urlStr;
            this.threadNum = threadNum;
            this.fileName = fileName;
            Log.i(TAG,"downloadTask" + fileName);
        }
        
        
        @Override
        public void run() {
            FileDownloadThread[] fds = new FileDownloadThread[threadNum];
            try {
                URL url = new URL(urlStr);
                URLConnection conn = url.openConnection();
                //获取下载文件的总大小  
                fileSize = conn.getContentLength();
                //计算每个线程要下载的数据量
                blockSize = fileSize / threadNum;
                downloadSizeMore = (fileSize % threadNum) ;
                File file = new File(fileName);
                for(int i = 0; i < threadNum; i++ ) {
                     //启动线程，分别下载自己需要下载的部分  
                    
                    FileDownloadThread fdt = new FileDownloadThread(url, file, i*blockSize, (i+1)*blockSize - 1);
                    System.out.println("FileDownloadThread---->" + i);
                    Log.i(TAG,"FileDownloadThread---->" + i);
                    fdt.setName("Thread" + i);
                    fdt.start();
                    fds[i] = fdt;
                }
                
                
                boolean finished = false;
                while(!finished) {
                     // 先把整除的余数搞定
                    downloadedSize = downloadSizeMore;
                    finished = true;
                    for(int i=0; i < fds.length; i++){
                        downloadedSize += fds[i].getDownloadSize();
                        if(!fds[i].isFinished()){
                            finished = false;
                        }
                        
                    }
                    handler.sendEmptyMessage(0);
                    sleep(1000);
                }
            } catch (MalformedURLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        
    }
    
    
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    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"
    tools:context=".MainActivity"
    android:orientation="vertical" >

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Download" 
        android:id="@+id/downloadButton"/>
    <ProgressBar
        android:id="@+id/downloadBar"
         android:layout_width="200dp"
         android:layout_height="40dp"
         style="?android:attr/progressBarStyleHorizontal"
         android:visibility="gone"
         android:max="100"
         android:layout_gravity="center_vertical"/>
    <TextView
        android:id="@+id/myTextView"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"/>
</LinearLayout>

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.INTERNET"/>