Android implementation of multithreading breakpoint download method

This article describes the Android implementation of multithreaded breakpoint download method. Share to everyone for your reference. The implementation methods are as follows:

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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 B T Private TextView TV; Private EditText et; Boolean flag = true; Boolean stopflag = false; Private Handler Handler = new HandlER () {@Override public void handlemessage (. msg) {pb.setprogress (total); int max = Pb.getmax (); if (Total >= (m Ax-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 periodically update the UI if ("Start downloading". Equals (Bt.gettex T (). 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 {1000);//If total > = file Length message msg = new Me Ssage (); Handler. SendMessage (msg); catch (Interruptedexception e) {e.printstacktrace ();}} }}.start ();  //Start 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 ~ End of File * * 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 (); Class Downloadtask extends Thread {int threadid; String filepath; int startposition; int Endpositon; Public downloadtask (int threadid, String filepath, int startposition, int endpositon) {this.threadid = ThreadID; this.fil Epath = 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 (f Is); String str = new string (result); if (! "". Equals (str)) {int newstartposition = Integer.parseint (str); if (Newstartposition > startposition) {startposition = NE Wstartposition; }}//"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); s Ynchronized (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.len Gth ()); } }

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