Android note 4--Multi-threaded breakpoint Continuation

Multi-threaded breakpoint continuation is extremely important on any platform, and this part of knowledge is very important. The usual, use a picture to introduce today's content.

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The principle is also very simple multithreading is to separate a file into different parts to allow multiple threads to download, the breakpoint continues to use a text record of the current download, and then start reading the text download value can be.

Just look at the code.

public class Mainactivity extends Activity {String path = "Http://192.168.15.77:8080/QQPlayer.exe"; int threadcount = 3; int finishedthreadcount = 0; int currentpbprogress;private ProgressBar pb;private TextView TV; Handler Handler = new Handler () {public void Handlemessage (Android.os.Message msg) {Tv.settext ((long) pb.getprogress () * 100/pb.getmax () + "%");}; @Overrideprotected void OnCreate (Bundle savedinstancestate) {super.oncreate (savedinstancestate); Setcontentview ( R.layout.activity_main);//progress bar is used to display the current download progress, the total number of bytes downloaded as progress, the total size of the target file as MAXPB = (ProgressBar) Findviewbyid (R.ID.PB); TV = (TextView) Findviewbyid (r.id.tv);} public void Click (View v) {Thread t = new Thread () {@Overridepublic void run () {try {URL url = new URL (path); HttpURLConnection conn = (httpurlconnection) url.openconnection (); Conn.setrequestmethod ("GET"); Conn.setconnecttimeout (8000); Conn.setreadtimeout (8000); if (conn.getresponsecode () = = 200) {//Get the total length of the file to be downloaded int length = Conn.getcontentlength ();//Generate a temporary file locally, the temporary file size is consistent with the target file size file= New File (Environment.getexternalstoragedirectory (), GetFileName (path)); Randomaccessfile RAF = new Randomaccessfile (file, "RWD"); raf.setlength (length); Raf.close ();// Set the overall progress of the progress bar to the total length of the target file Pb.setmax (length);//calculate the lengths of each thread to be downloaded int size = length/threadcount;//Calculates the start and end positions for each thread for (int i = 0; i < T Hreadcount; i++) {int startIndex = i * size;int EndIndex = (i + 1) * SIZE-1;IF (i = = threadCount-1) EndIndex = LENGTH-1;//SYSTEM.O UT.PRINTLN ("thread" + i + "Download interval is:" + StartIndex + "~" + endIndex); new Downloadthread (StartIndex, EndIndex, i). Start ();}} catch (Exception e) {//TODO auto-generated catch Blocke.printstacktrace ();}}; T.start ();} String GetFileName (string path) {int index = Path.lastindexof ("/"); return path.substring (index + 1);} 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;} @Overridepublic void Run () {//Open childThe thread downloads the target file try {file fileprogess = new file (Environment.getexternalstoragedirectory (), ThreadId + ". txt"); int lasttotal = 0; Determine if the text temporary file exists if (fileprogess.exists ()) {FileInputStream FIS = new FileInputStream (fileprogess); BufferedReader br = new BufferedReader (new InputStreamReader (FIS));//Get on the progress of the download lasttotal = Integer.parseint ( Br.readline ());//Change the start location of the download, the data has been downloaded, do not go to request startindex + = Lasttotal;fis.close ();// Writes the total progress of the last download to the progress bar currentpbprogress + = lasttotal;pb.setprogress (currentpbprogress); handler.sendemptymessage (0);} SYSTEM.OUT.PRINTLN ("thread" + ThreadId + "The final download interval is:" + StartIndex + "~" + endIndex); URL url = new URL (path); HttpURLConnection conn = (httpurlconnection) url.openconnection (); Conn.setrequestmethod ("GET"); Conn.setconnecttimeout (8000); Conn.setreadtimeout (8000);//define the range of requested data Conn.setrequestproperty ("range", "bytes=" + StartIndex + "-" + EndIndex), if (conn.getresponsecode () = = 206) {//Stream data only startIndex to EndIndex interval, Does not contain all data for the target file InputStream is = Conn.getinputstream (); byte[] B = new Byte[1024];inT len;int total = lasttotal; File file= new file (Environment.getexternalstoragedirectory (), GetFileName (path)); Randomaccessfile RAF = new Randomaccessfile (file, "RWD");//change the starting position of writing data to the RAF Raf.seek (StartIndex); while (len = Is.read ( b))! =-1) {total + = Len; SYSTEM.OUT.PRINTLN ("Threads" + threadId + "bytes downloaded:" + total); Raf.write (b, 0, Len);//In order to complete the breakpoint continuation, while loop the progress of each download, are written in a text temp file randomaccessfile rafprogress = new Randomaccessfile (fileprogess, "RWD"); Rafprogress.write ((Total + ""). GetBytes ()); Rafprogress.close (); currentpbprogress + = len;//All threads each time a len-length byte is downloaded, it is written to the total progress of the progress bar pb.setprogress ( currentpbprogress); handler.sendemptymessage (0);} SYSTEM.OUT.PRINTLN ("thread" + threadId + "Download completed---------------------"), Raf.close () finishedthreadcount++;//Three threads all downloaded, To remove the text temp file synchronized (path) {if (Finishedthreadcount = = 3) {for (int i = 0; i < ThreadCount; i++) {File F = new file (En Vironment.getexternalstoragedirectory (), i + ". txt"), if (F.exists ()) F.delete ();} Finishedthreadcount = 0;}}} catch (Exception e) {//TODO auto-Generated catch Blocke.printstacktrace ();}}} 

Android note 4--Multi-threaded breakpoint Continuation