Blackberry - LabelField Dynamic Update Issues

I am trying to develop a BlackBerry app for a Storm2. I am facing a problem when trying to update a LabelField from a different instance of the app.

The program is working fine without updating this LabelField, but when I tried to add the code to update开发者_如何学Python the text, it becomes unresponsive after the "settext" line.

Am I missing something?

public class AgentTrackerScreen extends MainScreen
{
    public static LabelField _outputText;
    ...
}

public class BtService implements Runnable
{
    ...
    public void run() 
    {
        AgentTrackerScreen._outputtext.settext(
            "Something: " + btListener.vecDevices.size());
    }
    ...
}

You must make all user interface modifications on the event thread, or else lock the user interface before doing it. See BlackBerry UI Threading Basics for details.

(BTW, this is a common requirement in many user interface systems. Swing in Java SE has this requirement. So does WPF on Windows.)

Use either:

• invokeAndWait(Runnable r)
• invokeLater(Runnable r)
• synchronize on UiApplication.getEventLock()