java - How to implement thread in succession -

i implement transfer socket transfering pictures , check on server if picture ever loaded , if true not transfering picture change imageview.

i have client , server work transfer picture between 2 devices. want send hash of each pictures once @ each time before send them. dificulty on thread manager, have implement listener 1st thread (send / receive picture's hash on client / server) know when it's finished , start second thread (send / receive pictures on client / server). don't know if methodology ok because doesn't work (the server receive hash on start not other).

i hope clear, here parts of code concerned, can give me solution.

server

private class receiverhash extends thread {

    private list<tasklistener> listeners = new arraylist<tasklistener>();      public void addlistener(tasklistener listener) {         listeners.add(listener);     }      void gettaskstate(boolean state) {         (tasklistener listener : listeners) {             listener.gettaskstate(state);         }     }      @override     public void run() {         try {             serversocket serversocket = new serversocket(socketserverport);              socket socket = serversocket.accept();             inputstream inputstream = socket.getinputstream();             bufferedreader br = new bufferedreader(new inputstreamreader(inputstream));              while (true) {                 string str = br.readline();          // lecture du message                 if (str.equals("end")) {                     serversocket.close();                     gettaskstate(true);                     break;                 }                 hashlist.add(str);                 log.d("hash_receiver_log", str);   // log debug hash             }         } catch (ioexception e) {             e.printstacktrace();         }     } }  private class receiver extends thread {      int pos = 0;     int cmpt = 0;      @override     public void run() {         // create serversocket using specified port         try {             serversocket serversocket = new serversocket(socketserverport);             while (true) {                  //checkfileexist();                 file f = new file(getfilesdir(), "img" + integer.tostring(pos) + ".png");                 filelist.add(f);                 log.d("hash_receiver_log", "attente d'une réponse du client");                 socket socket = serversocket.accept();                 log.d("hash_receiver_log", "reception d'une réponse");                 f.createnewfile();                  inputstream inputstream = socket.getinputstream();                 outputstream outputstream = new fileoutputstream(f);                  byte[] bytes = new byte[2 * 1024];                 int count;                  while ((count = inputstream.read(bytes)) > 0) {                         log.d("receiver_cmpt", integer.tostring(cmpt));                         outputstream.write(bytes, 0, count);                         cmpt = cmpt + count;                 }                 mybitmap = bitmapfactory.decodefile(f.getabsolutepath());                 runonuithread(new runnable() {                     @override                     public void run() {                         imgdiapo.setimagebitmap(mybitmap);                     }                 });             }         } catch (ioexception e) {             e.printstacktrace();         }     } } 

how use listener on activity :

receiverhash receiverhash = new receiverhash();     receiverhash.start();     receiverhash.addlistener(this); 

client

public class sender extends asynctask<void, void, void> { private string dstaddress; private int dstport; private string fpath;  public sender(string address, int port, string path) {     dstaddress = address;     dstport = port;     fpath = path;  }  @override protected void doinbackground(void... arg0) {      socket socket = null;     try {         socket = new socket(dstaddress, dstport);          fileinputstream inputstreamsend = new fileinputstream(fpath);         outputstream outputstreamsend = socket.getoutputstream();         byte[] buffer = new byte[2 * 1024];         int count;         while ((count = inputstreamsend.read(buffer)) > 0) {             outputstreamsend.write(buffer, 0, count);         }         outputstreamsend.close();         inputstreamsend.close();     } catch (ioexception e) {         e.printstacktrace();     } {         try {             if (socket != null) {                 socket.close();             }         } catch (ioexception e) {             e.printstacktrace();         }     }     return null; }  public class hashsender extends asynctask<void, void, void>  { private string dstaddress; private int dstport; string hash; //private arraylist <string> listhash; private list<tasklistener> listeners = new arraylist<tasklistener>();  public hashsender(string address, int port, string path) throws ioexception, nosuchalgorithmexception {     dstaddress = address;     dstport = port;     hash = sha1(new file(path)); //methode encryption in sha1 }   public void addlistener(tasklistener listener) {     listeners.add(listener); } void gettaskstate(boolean state) {     (tasklistener listener : listeners) {         listener.gettaskstate(state);     } }  @override protected void onpostexecute(void v) {     gettaskstate(true); }  @override protected void doinbackground(void... arg0) {      socket socket = null;      try {         socket = new socket(dstaddress, dstport);          outputstream outputstreamsend = socket.getoutputstream();         bufferedwriter buf = new bufferedwriter(new outputstreamwriter(outputstreamsend));         buf.write(hash);         buf.newline();         buf.flush();         log.d("toto", hash);         buf.write("end");         buf.newline();         buf.flush();         outputstreamsend.close();     } catch (ioexception e) {         e.printstacktrace();     } {         try {             if (socket != null) {                 socket.close();             }         } catch (ioexception e) {             e.printstacktrace();         }     }     return null; } 

how use listener on activity :

hashsender hashsender = new hashsender(dstaddress.get(i), dstport, selecteditempath.get(pos));                     hashsender.addlistener(controlsactivity.this);                     hashsender.execute();