Android implementation of Multithreading breakpoint download method _android

This article illustrates the way Android implements multithreaded breakpoint downloads. Share to everyone for your reference. The implementation method is as follows:

Package cn.itcast.download; 
Import Java.io.File; 
Import Java.io.FileInputStream; 
Import java.io.FileNotFoundException; 
Import Java.io.FileOutputStream; 
Import java.io.IOException; 
Import Java.io.InputStream; 
Import Java.io.RandomAccessFile; 
Import java.net.HttpURLConnection; 
Import java.net.MalformedURLException; 
Import java.net.ProtocolException; 
Import Java.net.URL; 
Import Cn.itcast.mutiledownload.StreamTool; 
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; 
Import Android.widget.TextView; 
Import Android.widget.Toast; 
  public class Mutiledownloadactivity extends activity implements Onclicklistener {private ProgressBar PB; 
  Private Button BT; 
  Private TextView TV; 
  Private EditText et; 
  Boolean flag = true; Boolean Stopflag =False Private Handler Handler = new Handler () {@Override public void Handlemessage (msg) {Pb.setprogre 
      SS (total); 
      int max = Pb.getmax (); 
        if (total >= (max-1)) {total = max; 
      Flag = false; 
      int result = Total * 100/MAX; 
      Tv.settext ("Current progress:" + result + "%"); 
    Super.handlemessage (msg); 
  } 
  }; 
  int total = 0; 
    @Override public void OnCreate (Bundle savedinstancestate) {super.oncreate (savedinstancestate); 
    Setcontentview (R.layout.main); 
    PB = (ProgressBar) This.findviewbyid (R.ID.PB); 
    BT = (Button) This.findviewbyid (R.ID.BT); 
    TV = (TextView) This.findviewbyid (r.id.tv_process); 
    ET = (edittext) This.findviewbyid (r.id.et); 
  Bt.setonclicklistener (this); 
      @Override public void OnClick (View v) {switch (V.getid ()) {case R.ID.BT://Create a child thread to update the UI periodically 
       if ("Start Download". Equals (Bt.gettext (). toString ())) {Bt.settext ("paused"); Stopflag = false; 
        Start Download} else {bt.settext ("start download"); 
      Stopflag = true; 
            New Thread () {@Override public void run () {super.run (); 
                while (flag) {try {sleep (1000); 
                If total > = file length msg = new Message (); 
              Handler.sendmessage (msg); 
              catch (Interruptedexception e) {e.printstacktrace (); 
 
        }}}.start (); 
        Start the download operation String path = Et.gettext (). toString (). Trim (); 
          if ("". Equals (Path)) {Toast.maketext (this, "path cannot be empty", 1). Show (); 
        Return 
          try {URL url = new URL (path); 
          HttpURLConnection conn = (httpurlconnection) URL. OpenConnection (); 
          Conn.setrequestmethod ("get"); 
 Conn.setconnecttimeout (5000);         Conn.setrequestproperty ("User-agent", "mozilla/4.0" (compatible; MSIE 6.0; Windows NT 5.1; 
          SV1) "); 
          int code = Conn.getresponsecode (); 
            if (code = =) {int len = conn.getcontentlength (); 
            Randomaccessfile file = new Randomaccessfile ("/mnt/sdcard/" + getfilenname (Path), "RWD"); 
            1. Set the local file size consistent with the file size of the server file.setlength (len); 
            Sets the maximum value of the progress bar Pb.setmax (LEN); 
            2. Suppose to open 3 threads int threadnumber = 3; 
            int blocksize = Len/threadnumber; /** * Thread 1 0~ blocksize thread 2 1*bolocksize ~ 2*blocksize Thread 3 * 2*blocksize ~ File End * 
              /for (int i = 0; i < threadnumber; i++) {int startposition = i * blocksize; 
              int Endpositon = (i + 1) * BLOCKSIZE; if (i = = (threadnumber-1)) {//Last thread EndposIton = Len; 
              } downloadtask task = new Downloadtask (i, Path, startposition, Endpositon); 
            Task.start (); 
          (Exception e) {Toast.maketext (this, "Exception on Download", 0). Show (); 
        E.printstacktrace (); 
    } break; 
    Class Downloadtask extends Thread {int threadid; 
    String filepath; 
    int startposition; 
    int Endpositon; Public downloadtask (int threadid, String filepath, int startposition, int endpositon) {this.threadid = th 
      Readid; 
      This.filepath = filepath; 
      This.startposition = startposition; 
    This.endpositon = Endpositon; @Override public void Run () {try {file Postionfile = new file ("/mnt/sdcard/" + ThreadID +). 
        TXT "); 
        URL url = new URL (filepath); 
        HttpURLConnection conn = (httpurlconnection) URL. OpenConnection (); System.OUT.PRINTLN ("thread" + ThreadID + "is downloading" + "start position:" + startposition + "End position" + Endpositon); 
          if (postionfile.exists ()) {FileInputStream FIS = new FileInputStream (postionfile); 
          Byte[] result = Streamtool.getbytes (FIS); 
          String str = new string (result); if (! "". 
            Equals (str)) {int newstartposition = Integer.parseint (str); 
            if (Newstartposition > startposition) {startposition = newstartposition;  }}//' range ', ' bytes=2097152-4194303 ' conn.setrequestproperty (' range ', ' bytes= ' 
        + startposition + "-" + Endpositon); 
        Conn.setrequestmethod ("get"); 
        Conn.setconnecttimeout (5000); Conn.setrequestproperty ("User-agent", "mozilla/4.0" (compatible; MSIE 6.0; Windows NT 5.1; 
        SV1) "); 
        InputStream is = Conn.getinputstream (); Randomaccessfile file = new Randomaccessfile ("/MNT/SDCArd/"+ getfilenname (filepath)," RWD "); 
        Sets the data from which location of the file to write File.seek (startposition); 
        byte[] buffer = new byte[1024]; 
        int len = 0; 
        Represents the location of the server data currently being read, while this value has been stored in the location of the file int currentpostion = startposition; Creates a file object that records the download location of the current file while (len = is.read (buffer)!=-1) {if (Stopflag) {return 
          ; 
          } file.write (buffer, 0, Len); 
          Synchronized (mutiledownloadactivity.this) {total = Len; 
          } currentpostion = Len; 
          The currentpostion information needs to be persisted to the storage device String position = currentpostion + ""; 
          FileOutputStream fos = new FileOutputStream (postionfile); 
          Fos.write (Position.getbytes ()); 
          Fos.flush (); 
        Fos.close (); 
        } file.close (); 
        SYSTEM.OUT.PRINTLN ("thread" + threadid + "Download Complete"); 
        Delete the file after the thread has been downloaded if (postionfile.exists ()) {  Postionfile.delete (); 
      } catch (Exception e) {e.printstacktrace (); 
    } super.run (); 
    } public string Getfilenname (string path) {int start = Path.lastindexof ("/") + 1; 
  Return path.substring (Start, path.length ()); } 
}

I hope this article will help you with your Android program.