Implementation of fieldchange listner in blackberry

//import packages manually or otherwise it comes bydefault
import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;
ButtonField Enterbutton;//Declare a button field inside your class.
//this goes inside constructor.
Enterbutton = new ButtonField("Enter",ButtonField.FOCUSABLE);
FieldChangeListener enterlistner = new FieldChangeListener()//implementing fieldchange listner named as enterlistner
{
public void fieldChanged(Field field, int context)
{
if(field==Enterbutton)
{
Dialog.alert("button clicked");
}
}
};

Enterbutton.setChangeListener(enterlistner);// set button to listen for particular listner.