title: Why button on screen not effect when I use postGlobalScreen to push this screen?
body: <p>I edit Blackberry_App_Descriptor.xml to make my app is "Auto run on start up". My app have 3 classes, myApp, screen1 and screen2. MyApp with main method to push screen1. in screen1 have a button to push screen 2. It run OK when I launch appplication manualy. (click icon of App )</p>
  
  <p>Problem is:</p>
  
  <p>I use RealTimeListener to always check time each minutes, if it is 1h30 it will push screen1, ( I used method postGlobalScreen to push Screen1 ). And it pushed success. But i can use the button on this screen1, I clicked it and it not push to screen2.</p>
  
  <p>I try to use Alternate Entry point to check time and push screen1 but it have the same result.</p>
  
  <p>Can anybody help me solve and explain clearly about this problem ?</p>
  
  <pre><code>// MyApp.java
     public class MyApp extends UiApplication implements RealtimeClockListener
      {
          /**
           * Entry point for application
           * @param args Command line arguments (not used)
           */ 
  
          public static void main(String[] args)
          {
              // Create a new instance of the application and make the currently
              // running thread the application's event dispatch thread.
              MyApp theApp = new MyApp();  
              theApp.enterEventDispatcher();
          }
  
  
          /**
           * Creates a new MyApp object
           */
          public MyApp()
          {        
              // Push a screen onto the UI stack for rendering.
              pushScreen(new Screen1());
              addRealtimeClockListener(this);
  
  
          }
  
  
          public void clockUpdated() {
              int hour = Calendar.getInstance().get(Calendar.HOUR_OF_DAY);
              int minute = Calendar.getInstance().get(Calendar.MINUTE);
              if(hour==1 &amp;&amp; minute == 30){    
  
                  UiApplication.getUiApplication().pushGlobalScreen(new Screen1(),1,UiEngine.GLOBAL_MODAL);           
              }
  
          }
  
  
  
      }
  
  
  //Screen1.java
  public final class Screen1 extends MainScreen implements FieldChangeListener
  {
      /**
       * Creates a new MyScreen object
       */
      ButtonField button;
      public Screen1()
      {        
          button = new ButtonField("Screen 1 ");
          button.setChangeListener(this);
          add(button);
  
  
      }
      public void fieldChanged(Field field, int context) {
          if(field==button){
              UiApplication.getUiApplication().pushScreen(new Screen2());
  
          }
  
      }
  
  }
  
  //Screen2.java
  public final class Screen2 extends MainScreen implements FieldChangeListener
  {
      /**
       * Creates a new MyScreen object
       */
      ButtonField button;
      public Screen2()
      {        
          button = new ButtonField("Screen2");
          button.setChangeListener(this);
          add(button);
  
  
      }
      public void fieldChanged(Field field, int context) {
          if(field==button){
              UiApplication.getUiApplication().pushScreen(new Screen1());
          }
  
      }
  }
  </code></pre>