Uncaught exception: blocking operation not permitted on event dispatch thread on BlackBerry

I have a HttpConnection thread class. when ı stop httpConnection, I show this messeage. how should ı stop httpConnection??

Blackberry Output Console:

RuntimeException
blocking operation not permitted on event dispatch thread
net_rim_cldc-10
 EventThreadCheck
 throwException
 0x3434
net_rim_cldc_io_tcp
 Protocol
 <private>
 0x18B8
net_rim_cldc_io_tcp
 Protocol
 outputStreamClosed
 0xB2D
net_rim_cldc_io_tcp
 TcpOutputStream
 close
 0x40BF
net_rim_os-2
 ClientProtocol
 close
 0x154E
CepVizyon-2
 Http
 cancel
 0x174F
CepVizyon-2
 Camera
 cancel
 0x6E7
CepVizyon
 ViewCam
 close
 0xE79
net_rim_cldc-7
 Screen
 onClose
 0x5DAC
net_rim_cldc-7
 Screen
 keyCharUnhandled
 0x5C58
net_rim_cldc-9
 MainScreen
 keyCharUnhandled
 0x23D7
net_rim_cldc-7
 Screen
 dispatchKeyEvent
 0x51DB
net_rim_cldc-7
 Screen
 processKeyEvent
 0x718D
net_rim_cldc-7
 UiEngineImpl
 processMessage
 0x9E3C
net_rim_cldc-4
 Application
 processNextMessage
 0x1073
net_rim_cldc-4
 Application
 enterEventDispatcher
 0x775
CepVizyon-2
 CepVizyonMain
 main
 0x1175

parts of My Connection class:

public abstract class Http extends Thread{
    protected HttpConnection httpConnection;
HttpConnectionFactory factory;
protected static Base64 base64;

private boolean cancel = false;
/** bağlantının yapılcağı adres */
protected String url = "";
/** paremetre olarak gönderilecek data */
protected String queryString = "";

    ...

public void cancel() {
        try {
            if (httpConnection != null)
                httpConnection.close();
            if(factory!=null)
                factory.cancel();
        } catch (IOException ex) {
        }
        cancel = true;
    }

part of my screen class:

public void close() {
        super.close();
        Static开发者_StackOverflow社区Var.ActiveCam.cancel();
//      CameraListScreen screen = new CameraListScreen();
//      UiApplication.getUiApplication().pushScreen(screen);
//
    }

and part of Camera Class/*ActiveCam's cancel is here/:

// finishes connection.
    public void cancel() {
        setConnected(false);
        if (mjpeghttp != null) {
            mjpeghttp.cancel();
            //mjpeghttp.interrupt();
            //mjpeghttp = null;

        }
            }

It looks like your HttpConnection is accessed from a background (non UI) thread which is good. However your UI calls close() directly which may block. You should consider spawning another thread to do the close().

You must work with screen only from event thread

 //safely (recommended)
 Application.getApplication().invokeLater(new Runnable() {
        public void run() {
            //your code here
         }
 });

or

//fast 
synchronized(Application.getEventLock()) {
   //your code here
 }