How to Implement multi‑thread breakpoint download in Android

How to Implement multi‑thread breakpoint download in Android

This example describes how to implement multi‑thread breakpoint download in Android. Share it with you for your reference. The specific implementation method is 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 bt; Private TextView TV; Private EditText et; Boolean flag = true; Boolean stopflag = false; Private Handler handler = new Handler (){ @ Override Public void handleMessage (Message msg ){ Pb. setProgress (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 subthread to regularly update the ui If ("start to 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 Message 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 blank", 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 = 200 ){ Int len = conn. getContentLength (); RandomAccessFile file = new RandomAccessFile ( "/Mnt/sdcard/" + getFilenName (path), "rwd "); // 1. Set the local file size to the same as the Server File Size File. setLength (len ); // Set the maximum value of the progress bar Pb. setMax (len ); // 2. Assume that three threads are enabled. 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 )){ // The last thread Endpositon = len; } DownLoadTask task = new DownLoadTask (I, path, Startposition, endpositon ); Task. start (); } } } Catch (Exception e ){ Toast. makeText (this, "Download exception", 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 = threadid; 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 + "downloading" + "start position :" + Startposition + "end position" + endpositon ); If (postionfile. exists ()){ FileInputStream FCM = new FileInputStream (postionfile ); Byte [] result = StreamTool. getBytes (SOx ); 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 "); // Set the position where the data is written from the file File. seek (startposition ); Byte [] buffer = new byte [1024]; Int len = 0; // Represents the location of the server data currently read, and the location of the file with this value already stored Int currentPostion = startposition; // Create a file object to record 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 persistently stored on 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 completed "); // Delete the object after the thread download is complete. 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 design your Android program.