Question

I am calling a popupscreen where I have objectchoicefield where I select a data from dropdown and set the value in static variable. I need to read this value in the constructor of the mainscreen from where popupscreen was called.

How to do this ?I want the same screen to be reloaded with the data that I selected now.

Initially when I launch the app I see the Ascreen with some data ,once I click on an image I call a popup screen ,where I select some data ,now I want to reload AScreen with the selected value,once popupscreen is closed.

Ascreen

Public AScreen(){
    String timezone_static = MyPopup.ocfDATA;
}
if (field == bitmapField1) {

    UiApplication.getUiApplication().pushScreen(new MyPopup(screen));

}

public class MyPopup extends PopupScreen {
    ObjectChoiceField ocf;
    NativeScreen deligate = null;
    public static String ocfDATA;

    public MyPopup(final NativeScreen deligate) {

        super(new VerticalFieldManager(), Field.FOCUSABLE);
        this.deligate = deligate;
        // this listener 'listens' for any event (see at the bottom)
        FieldListener listener = new FieldListener();

        TimeZone[] zone = TimeZoneUtilities.getAvailableTimeZones();
        ocf = new ObjectChoiceField("Set Timezone", zone);
        ocf.setChangeListener(listener);
        add(ocf);
    }

    class FieldListener implements FieldChangeListener {
        public void fieldChanged(Field f, int context) {

            if (f == ocf) {

                Object ob = ocf.getChoice(ocf.getSelectedIndex());
                String str = ob.toString();
                ocfDATA = str;
                deligate.valueChanged(str);
                Dialog.alert(str);
                close();
            }
        }
    }

Answer 1

i am explaining some of flow how to navigate from one screen another screen with values.
this is simple way in your main screen

protected void onExposed() {
        String timezone_static = MyPopup.ocfDATA;
    }

otherwise you want to know more to navigate from one place to another is just understand following code

package mypackage;

import java.util.TimeZone;

import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;
import net.rim.device.api.ui.UiApplication;
import net.rim.device.api.ui.component.ButtonField;
import net.rim.device.api.ui.component.LabelField;
import net.rim.device.api.ui.component.ObjectChoiceField;
import net.rim.device.api.ui.container.MainScreen;
import net.rim.device.api.ui.container.PopupScreen;
import net.rim.device.api.ui.container.VerticalFieldManager;
import net.rim.device.api.util.TimeZoneUtilities;

public final class MyScreen extends MainScreen implements FieldChangeListener
{
    private ButtonField btn;
    private LabelField zone_name;
    public MyScreen()
    { 
        //may be you have lots of parameters in constructers those all are in live state only design values you can delete

        CreateGui("Default Zone");// add all your design in this function 
    }
    public void CreateGui(String selcetd_time_zone)
    {
        setTitle(selcetd_time_zone);
        zone_name=new LabelField(selcetd_time_zone, Field.FOCUSABLE);
        btn=new ButtonField("select timezone",Field.FOCUSABLE);
        btn.setChangeListener(this);
        add(btn);
        add(zone_name);
    }
    public void ReloadScreenAccordingToNewZone(String zone_name)
    {
        synchronized (UiApplication.getEventLock()) {
            deleteAll();//clean your GUI
            invalidate();
            CreateGui(zone_name);
        }

    }
    public void fieldChanged(Field field, int context) {
        if(field==btn)
        {
             UiApplication.getUiApplication().pushScreen(new MyPopup(MyScreen.this));
        }
    }
}
class MyPopup extends PopupScreen implements FieldChangeListener{
    ObjectChoiceField ocf;
    MyScreen deligate = null;
    public MyPopup(MyScreen deligate) {
        super(new VerticalFieldManager(), Field.FOCUSABLE);
        this.deligate = deligate;
        TimeZone[] zone = TimeZoneUtilities.getAvailableTimeZones();
        ocf = new ObjectChoiceField("Set Timezone", zone);
        ocf.setChangeListener(this);
        add(ocf);
    }
    public void fieldChanged(Field field, int context) {
        if(field==ocf)
        {
            Object ob = ocf.getChoice(ocf.getSelectedIndex());
            deligate.ReloadScreenAccordingToNewZone(ob.toString());
            close();
        }

    }

}

My suggestion is that if you want to update more design from another class then just separate out the constructor and design

like

all your design write in one method suppose CreateGui(); call this method from constructer;
if you want to reload update design just call CreateGui from onExposed() method