import java.io.BufferedReader;

 import java.io.File;

 import java.io.FileInputStream;

 import java.io.InputStream;

 import java.io.InputStreamReader;

 import java.io.RandomAccessFile;

 import java.net.HttpURLConnection;

 import java.net.URL;

 import android.os.Bundle;

 import android.os.Environment;

 import android.os.Handler;

 import android.app.Activity;

 import android.view.Menu;

 import android.view.View;

 import android.widget.ProgressBar;

 import android.widget.TextView;

 public class MainActivity extends Activity {

     static int ThreadCount = 3;

     static int finishedThread = 0;

     int currentProgress;

     String fileName = "QQPlayer.exe";

     //确定下载地址

     String path = "http://192.168.13.13:8080/" + fileName;

     private ProgressBar pb;

     TextView tv;

     Handler handler = new Handler(){

         public void handleMessage(android.os.Message msg) {

             //把变量改成long，在long下运算

             tv.setText((long)pb.getProgress() * 100 / pb.getMax() + "%");

         }

     };

     @Override

     protected void onCreate(Bundle savedInstanceState) {

         super.onCreate(savedInstanceState);

         setContentView(R.layout.activity_main);

         pb = (ProgressBar) findViewById(R.id.pb);

         tv = (TextView) findViewById(R.id.tv);

     }

     public void click(View v){

         Thread t = new Thread(){

             @Override

             public void run() {

                 //发送get请求，请求这个地址的资源

                 try {

                     URL url = new URL(path);

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

                     conn.setRequestMethod("GET");

                     conn.setConnectTimeout(5000);

                     conn.setReadTimeout(5000);

                     if(conn.getResponseCode() == 200){

                         //拿到所请求资源文件的长度

                         int length = conn.getContentLength();

                         //设置进度条的最大值就是原文件的总长度

                         pb.setMax(length);

                         File file = new File(Environment.getExternalStorageDirectory(), fileName);

                         //生成临时文件

                         RandomAccessFile raf = new RandomAccessFile(file, "rwd");

                         //设置临时文件的大小

                         raf.setLength(length);

                         raf.close();

                         //计算出每个线程应该下载多少字节

                         int size = length / ThreadCount;

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

                             //计算线程下载的开始位置和结束位置

                             int startIndex = i * size;

                             int endIndex = (i + 1) * size - 1;

                             //如果是最后一个线程，那么结束位置写死

                             if(i == ThreadCount - 1){

                                 endIndex = length - 1;

                             }

 //                            System.out.println("线程" + i + "的下载区间是：" + startIndex + "---" + endIndex);

                             new DownLoadThread(startIndex, endIndex, i).start();

                         }

                     }

                 } catch (Exception e) {

                     // TODO Auto-generated catch block

                     e.printStackTrace();

                 }

             }

         };

         t.start();

     }

     class DownLoadThread extends Thread{

         int startIndex;

         int endIndex;

         int threadId;

         public DownLoadThread(int startIndex, int endIndex, int threadId) {

             super();

             this.startIndex = startIndex;

             this.endIndex = endIndex;

             this.threadId = threadId;

         }

         @Override

         public void run() {

             //再次发送http请求，下载原文件

             try {

                 File progressFile = new File(Environment.getExternalStorageDirectory(), threadId + ".txt");

                 //判断进度临时文件是否存在

                 if(progressFile.exists()){

                     FileInputStream fis = new FileInputStream(progressFile);

                     BufferedReader br = new BufferedReader(new InputStreamReader(fis));

                     //从进度临时文件中读取出上一次下载的总进度，然后与原本的开始位置相加，得到新的开始位置

                     int lastProgress = Integer.parseInt(br.readLine());

                     startIndex += lastProgress;

                     //把上次下载的进度显示至进度条

                     currentProgress += lastProgress;

                     pb.setProgress(currentProgress);

                     //发送消息，让主线程刷新文本进度

                     handler.sendEmptyMessage(1);

                     fis.close();

                 }

                 System.out.println("线程" + threadId + "的下载区间是：" + startIndex + "---" + endIndex);

                 HttpURLConnection conn;

                 URL url = new URL(path);

                 conn = (HttpURLConnection) url.openConnection();

                 conn.setRequestMethod("GET");

                 conn.setConnectTimeout(5000);

                 conn.setReadTimeout(5000);

                 //设置本次http请求所请求的数据的区间

                 conn.setRequestProperty("Range", "bytes=" + startIndex + "-" + endIndex);

                 //请求部分数据，相应码是206

                 if(conn.getResponseCode() == 206){

                     //流里此时只有1/3原文件的数据

                     InputStream is = conn.getInputStream();

                     byte[] b = new byte[1024];

                     int len = 0;

                     int total = 0;

                     //拿到临时文件的输出流

                     File file = new File(Environment.getExternalStorageDirectory(), fileName);

                     RandomAccessFile raf = new RandomAccessFile(file, "rwd");

                     //把文件的写入位置移动至startIndex

                     raf.seek(startIndex);

                     while((len = is.read(b)) != -1){

                         //每次读取流里数据之后，同步把数据写入临时文件

                         raf.write(b, 0, len);

                         total += len;

                         System.out.println("线程" + threadId + "下载了" + total);

                         //每次读取流里数据之后，把本次读取的数据的长度显示至进度条

                         currentProgress += len;

                         pb.setProgress(currentProgress);

                         //发送消息，让主线程刷新文本进度

                         handler.sendEmptyMessage(1);

                         //生成一个专门用来记录下载进度的临时文件

                         RandomAccessFile progressRaf = new RandomAccessFile(progressFile, "rwd");

                         //每次读取流里数据之后，同步把当前线程下载的总进度写入进度临时文件中

                         progressRaf.write((total + "").getBytes());

                         progressRaf.close();

                     }

                     System.out.println("线程" + threadId + "下载完毕-------------------小志参上！");

                     raf.close();

                     finishedThread++;

                     synchronized (path) {

                         if(finishedThread == ThreadCount){

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

                                 File f = new File(Environment.getExternalStorageDirectory(), i + ".txt");

                                 f.delete();

                             }

                             finishedThread = 0;

                         }

                     }

                 }

             } catch (Exception e) {

                 // TODO Auto-generated catch block

                 e.printStackTrace();

             }

         }

     }

 }