PC版与Android手机版带断点续传的多线程下载

 public class MultiDownload {
    static int ThreadCount = ;
    static int finishedThread = ;
    //确定下载地址
    static String filename = "EditPlus.exe";
    static String path = "http://...:/"+filename;
    public static void main(String[] args) {
      //、发送get请求，去获得下载文件的长度
     try {
       URL url = new URL(path);
       HttpURLConnection conn = (HttpURLConnection) url.openConnection();
       conn.setRequestMethod("GET");
       conn.setConnectTimeout();
       conn.setReadTimeout();
       if (conn.getResponseCode()==) {
         //如果请求成功，拿到所请求资源文件的长度
         int length = conn.getContentLength();
         //、生成一个与原文件同样的大小的临时文件，以免下载一半存储空间不够了
         File file = new File(filename);//演示，所以将保存的文件目录放在工程的同目录
         //使用RandomAccessFile 生成临时文件，可以用指针定位文件的任意位置，
         //而且能够实时写到硬件底层设备，略过缓存，这对下载文件是突然断电等意外是有好处的
         RandomAccessFile raf = new RandomAccessFile(file, "rwd");//rwd, 实时写到底层设备
         //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个字节
         int size = length/ThreadCount;//如果有余数，负责最后一部分的线程负责下砸
         //开启多线程
         for (int threadId = ; threadId < ThreadCount; threadId++) {
           //计算每个线程下载的开始位置和结束位置
           int startIndex = threadId*size; // 开始 = 线程id * size
           int endIndex = (threadId+)*size - ; //结束 = （线程id + )*size - 
           //如果是最后一个线程，那么结束位置写死为文件结束位置
           if (threadId == ThreadCount - ) {
             endIndex = length - ;
           }
           //System.out.println("线程"+threadId+"的下载区间是： "+startIndex+"----"+endIndex);
           new DownloadThread(startIndex,endIndex,threadId).start();
         }
       }
     } catch (MalformedURLException e) {
       e.printStackTrace();
     } catch (IOException e) {
       e.printStackTrace();
     }
   }
 }
 class DownloadThread extends Thread{
   private int startIndex;
   private int endIndex;
   private int threadId;
   public DownloadThread(int startIndex, int endIndex, int threadId) {
     super();
     this.startIndex = startIndex;
     this.endIndex = endIndex;
     this.threadId = threadId;
   }
    public void run() {
      //每个线程再次发送http请求，下载自己对应的那部分数据
     try {
       File progressFile = new File(threadId+".txt");
       //判断进度文件是否存在，如果存在，则接着断点继续下载，如果不存在，则从头下载
       if (progressFile.exists()) {
         FileInputStream fis = new FileInputStream(progressFile);
         BufferedReader br = new BufferedReader(new InputStreamReader(fis));
         //从进度文件中度取出上一次下载的总进度，然后与原本的开始进度相加，得到新的开始进度
         startIndex += Integer.parseInt(br.readLine());
         fis.close();
       }
       System.out.println("线程"+threadId+"的下载区间是:"+startIndex+"----"+endIndex);
       //、每个线程发送http请求自己的数据
       URL url = new URL(MultiDownload.path);
       HttpURLConnection conn = (HttpURLConnection) url.openConnection();
       conn.setRequestMethod("GET");
       conn.setConnectTimeout();
       conn.setReadTimeout();
       //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，响应码是
       if (conn.getResponseCode()==) {
         //此时，流里只有ThreadCount分之一的原文件数据
         InputStream is = conn.getInputStream();
         byte[] b = new byte[];
         int len = ;
         int total = ;//total 用于保存断点续传的断点
         //拿到临时文件的输出流
         File file = new File(MultiDownload.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))!=-) {
           //每次读取流里数据之后，同步把数据写入临时文件
           raf.write(b, , len);
           total += len;
           //System.out.println("线程" + threadId + "下载了" + total);
           //生成一个一个专门用来记录下载进度的临时文件
           RandomAccessFile progressRaf = new RandomAccessFile(progressFile, "rwd");
           progressRaf.write((total+"").getBytes());
           progressRaf.close();
         }
         System.out.println("线程"+threadId+"下载完了---------------------");
         raf.close();
         //当所有的线程下载完之后，将进度文件删除
         MultiDownload.finishedThread++;
         synchronized (MultiDownload.path) {//所有线程使用同一个锁
           if (MultiDownload.finishedThread==MultiDownload.ThreadCount) {
             for (int i = ; i < MultiDownload.ThreadCount; i++) {
               File f = new File(i+".txt");
               f.delete();
             }
             MultiDownload.finishedThread=;
           }
         }
       }  
     } catch (Exception e) {
       e.printStackTrace();
     }
   }
 }

public class MainActivity extends Activity {
  static int ThreadCount = ;
  static int FinishedThread = ;
  int currentProgess;
  static String Filename = "QQPlayer.exe";
  static String Path = "http://...:/"+Filename;
  static MainActivity ma;
  static ProgressBar pb;
  static TextView tv;
  static Handler handler = new Handler(){
    public void handleMessage(android.os.Message msg){
      tv.setText((long)pb.getProgress()* /pb.getMax() +"%");
    };
  };
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ma = this;
    pb = (ProgressBar) findViewById(R.id.pb);
    tv = (TextView) findViewById(R.id.tv);
  }
  public void download(View v){
    Thread t = new Thread(){
      public void run() {
        //发送http请求获取文件的长度，创建临时文件
        try {
          URL url= new URL(Path);
          HttpURLConnection conn = (HttpURLConnection) url.openConnection();
          conn.setRequestMethod("GET");
          conn.setConnectTimeout();
          conn.setReadTimeout();
          if (conn.getResponseCode()==) {
            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);
            //生成一个与原文件相同大小的临时文件
            File file = new File(Environment.getExternalStorageDirectory(),Filename);
            RandomAccessFile raf = new RandomAccessFile(file, "rwd");
            raf.setLength(length);
            raf.close();
            //计算每个线程需要下载的数据大小
            int size = length/ThreadCount;
            //开启多线程
            for (int threadId = ; threadId < ThreadCount; threadId++) {
              int startIndex = threadId*size;
              int endIndex = (threadId + )*size - ;
              if (threadId==ThreadCount - ) {
                endIndex = length - ;
              }
              new DownloadThread(startIndex, endIndex, threadId).start();
            }
          }
        } catch (Exception e) {
          e.printStackTrace();
        }
      }
    };
    t.start();
  }
  class DownloadThread extends Thread{
    private int startIndex;
    private int endIndex;
    private int threadId;
    public DownloadThread(int startIndex, int endIndex, int threadId) {
      super();
      this.startIndex = startIndex;
      this.endIndex = endIndex;
      this.threadId = threadId;
    }
    public void run() {
      // 每个线程发送http请求自己的数据
      try{
        //先判断是不是断点续传
        File progessFile = new File(Environment.getExternalStorageDirectory(),threadId+".txt");
        if (progessFile.exists()) {
          FileReader fr = new FileReader(progessFile);
          BufferedReader br = new BufferedReader(fr);
          int lastProgess = Integer.parseInt(br.readLine());
          startIndex += lastProgess;
          //把上次下载的进度显示至进度条
          currentProgess +=lastProgess;
          pb.setProgress(currentProgess);
          //发消息，让主线程刷新文本进度
          handler.sendEmptyMessage();
          br.close();
          fr.close();
        }
        URL url = new URL(Path);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("GET");
        conn.setConnectTimeout();
        conn.setReadTimeout();
        conn.setRequestProperty("Range", "bytes="+startIndex+"-"+endIndex);
        if (conn.getResponseCode()==) {
          InputStream is = conn.getInputStream();
          byte[] buffer = new byte[];
          int len = ;
          int total = ;
          File file = new File(Environment.getExternalStorageDirectory(),Filename);
          RandomAccessFile raf = new RandomAccessFile(file, "rwd");
          raf.seek(startIndex);
          while ((len = is.read(buffer))!= -) {
            raf.write(buffer, , len);
            total += len;
            //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
            currentProgess += len;
            pb.setProgress(currentProgess);
            //发消息，让主线程刷新文本进度
            handler.sendEmptyMessage();
            //生成临时文件保存下载进度，用于断点续传，在所有线程现在完毕后删除临时文件
            RandomAccessFile progressRaf = new RandomAccessFile(progessFile, "rwd");
            progressRaf.write((total+"").getBytes());
            progressRaf.close();
          }
          raf.close();
          System.out.println("线程"+threadId+"下载完了");
          //当所有线程都下在完了之后，删除临时进度文件
          FinishedThread++;
          synchronized (Path) {
            if (FinishedThread==ThreadCount) {
              for (int i = ; i < ThreadCount; i++) {
                File f = new File(Environment.getExternalStorageDirectory(),i+".txt");
                f.delete();
              }
              FinishedThread=;
            }
          }
        }
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  }
}