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java.lang.IllegalThreadStateException in MIDlet

Posted on 2007-03-28
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Last Modified: 2013-12-29
Hi experts,

I tried to invoke web service in my Midlet in the commandAction, but it gives me the following Warning:

To avoid potential deadlock, operations that may block, such as
 networking, should be performed in a different thread than the
 commandAction() handler.

and didn't perfome web services calling

Then I have implemented Runnable, override run() and run my thread and it gives me the Exception:

java.lang.IllegalThreadStateException

this is my code:

/*
 * DBClient.java
 *
 * Created on March 21, 2007, 2:50 PM
 */

import java.rmi.RemoteException;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import login.*;

public class DBClient extends MIDlet implements CommandListener, Runnable {
   
   
    Form mainForm = new Form ("Welcome");
    TextField username = new TextField ("Uaername", "", 10, TextField.ANY);
    TextField password = new TextField ("Password", "", 10, TextField.PASSWORD);
    StringItem resultItem = new StringItem ("", "");
    Command getCommand = new Command ("Login", Command.SCREEN, 1);
    Thread myThread = new Thread();    
    boolean isThread = true;
   
    public DBClient(){
   
      mainForm.append (username);
      mainForm.append (password);
      mainForm.append (resultItem);
      mainForm.addCommand (getCommand);
      mainForm.setCommandListener (this);
       
   
    }//
   
   
    public void startApp() {
       
         Display.getDisplay(this).setCurrent(mainForm);
         
       
           
       
       
    }
   
    public void pauseApp() {
    }
   
    public void destroyApp(boolean unconditional) {
    }

   
           
   
public void commandAction (Command c, Displayable d) {
   
   
    if (c == getCommand ){
   
      try {
           myThread.start();
      }
      catch (Exception e) {
          e.printStackTrace ();
          resultItem.setLabel ("Error:");
          resultItem.setText (e.toString ());
      }
    }// end of if
    }


 public void run(){
 
 while(isThread){
     
     Action a = new Action();
     
     String myresult = a.invokeLogin(username.getString(),password.getString());
     resultItem.setText(myresult);
     try{
    myThread.wait(1000);
     
     }
     catch(Exception e){}// end of catch
    isThread = false;
     
   
 }// end of while
 }// end of run thread


}
0
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Question by:Sh_Rashed
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7 Comments
 
LVL 30

Expert Comment

by:Mayank S
ID: 18808950
>> resultItem.setText(myresult);

You cannot modify the UI from another thread - you should do it from the Event Dispatch Thread.
0
 
LVL 12

Expert Comment

by:keyurkarnik
ID: 18834846
What mayank has stated above is NOT the issue . You can change the resultItem from anywhere you want.

Your problem is this :

You have created a thread myThread = new Thread();
and then you are doing myThread.start()

whereas your run method is in your DBClient class.

The code will not work this way. You should do it either using a separate class that extends thread or use an inner class or use an anonymous impelmentation of run.

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LVL 12

Accepted Solution

by:
keyurkarnik earned 800 total points
ID: 18834849
Here is a solution with an anonymous implementation :



/*
 * DBClient.java
 *
 * Created on March 21, 2007, 2:50 PM
 */

import java.rmi.RemoteException;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class DBClient extends MIDlet implements CommandListener
{


      Form mainForm = new Form("Welcome");
      TextField username = new TextField("Uaername", "", 10, TextField.ANY);
      TextField password = new TextField("Password", "", 10, TextField.PASSWORD);
      StringItem resultItem = new StringItem("", "");
      Command getCommand = new Command("Login", Command.SCREEN, 1);
      Thread myThread = new Thread();
      boolean isThread = true;

      public DBClient()
      {

            mainForm.append(username);
            mainForm.append(password);
            mainForm.append(resultItem);
            mainForm.addCommand(getCommand);
            mainForm.setCommandListener(this);


      }//


      public void startApp()
      {

            Display.getDisplay(this).setCurrent(mainForm);


      }

      public void pauseApp()
      {
      }

      public void destroyApp(boolean unconditional)
      {
      }


      public void commandAction(Command c, Displayable d)
      {


            if (c == getCommand)
            {

                  try
                  {
                        new Thread()
                        {

                              public void run()
                              {

                                    while (isThread)
                                    {

                                          Action a = new Action();

                                          String myresult = a.invokeLogin(username.getString(), password.getString());
                                          resultItem.setText(myresult);
                                          try
                                          {
                                                sleep(1000);

                                          }
                                          catch (Exception e)
                                          {
                                          }// end of catch
                                          isThread = false;


                                    }// end of while
                              }// end of run thread

                        }.start();
                  }
                  catch (Exception e)
                  {
                        e.printStackTrace();
                        resultItem.setLabel("Error:");
                        resultItem.setText(e.toString());
                  }
            }// end of if
      }

}
0
 
LVL 12

Expert Comment

by:keyurkarnik
ID: 18834850
The rest is same - just take a look at the run method -
I have removed it from your class and put it as an anonymous method in the commandAction method.
0
 

Author Comment

by:Sh_Rashed
ID: 18834897
Thank u so much it works
0
 
LVL 12

Expert Comment

by:keyurkarnik
ID: 18834902
See - the problem you had was that you were starting a different thread - which actually had no runnable by doing myThread = new Thread().
thats why the illegal state exception
0

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