user-interface - Blackberry クリック イベント

Question

VerticalFieldManager に ImageButton があり、Horizo​​ntalFieldManager に VFM があります。周囲のフィールドのどこかをクリックすると、ImageButton クリック イベントが発生します。フィールド（VFMまたはHFM）ではなく、ImageButtonをクリックしたときにのみクリックイベントが発生するようにします。

コードは次のとおりです。

ImageButton Login = new ImageButton(configModel.getLoginButton(), FOCUSABLE|Field.FIELD_RIGHT, "login.png", "plogin.png",0x9cbe95);
HorizontalFieldManager hfm = new HorizontalFieldManager(USE_ALL_WIDTH);
VerticalFieldManager loginButtonVfm = new VerticalFieldManager(USE_ALL_WIDTH);

loginButtonVfm.add(Login);
hfm.add(loginButtonVfm);
add(hfm);


FieldChangeListener loginListener = new FieldChangeListener() { 
public void fieldChanged(Field field, int context) {
     Dialog.alert("Fired");
    }
}
Login.setChangeListener(loginListener); 

ImageButton クラスのコードは次のとおりです。

public class ImageButton extends Field{

        //Image Button Class 
        private String _label;
        private int _labelHeight;
        private int _labelWidth;
        private Font _font;

        private Bitmap _currentPicture;
        private Bitmap _onPicture;
        private Bitmap _offPicture;
        int color;

        public ImageButton(String text, long style ,String img, String img_hvr, int color){
            super(style);

            _offPicture = Bitmap.getBitmapResource(img);
            _onPicture = Bitmap.getBitmapResource(img_hvr);

            _font = Font.getDefault().derive(Font.BOLD, 7, Ui.UNITS_pt);
            _label = text;


            _labelHeight = _onPicture.getHeight();  
            _labelWidth = _onPicture.getWidth();

            this.color = color;

            _currentPicture = _offPicture;
        }
        public void setImage(String img){

            _offPicture = Bitmap.getBitmapResource(img); 
            _currentPicture = _offPicture;
        }

        /**
         * @return The text on the button
         */
        public void setText(String text){
            _label = text;
        }
            String getText(){
            return _label;
        }

        /**
         * Field implementation.
         * @see net.rim.device.api.ui.Field#getPreferredHeight()
         */
        public int getPreferredHeight(){
            return _labelHeight;
        }
        /**
         * Field implementation.
         * @see net.rim.device.api.ui.Field#getPreferredWidth()
         */
        public int getPreferredWidth(){
            return _labelWidth;
        }

        /**
         * Field implementation.  Changes the picture when focus is gained.
         * @see net.rim.device.api.ui.Field#onFocus(int)
         */
        protected void onFocus(int direction) {

             _currentPicture = _onPicture;
          //  invalidate();
            super.onFocus(direction);
        }

        /**
         * Field implementation.  Changes picture back when focus is lost.
         * @see net.rim.device.api.ui.Field#onUnfocus()
         */
        protected void onUnfocus() {
            _currentPicture = _offPicture;
            invalidate();
            super.onUnfocus();
        }

        /**
         * Field implementation.  
         * @see net.rim.device.api.ui.Field#drawFocus(Graphics, boolean)
         */
//      protected void drawFocus(Graphics graphics, boolean on) {
//          // Do nothing
//      }
        protected void drawFocus(Graphics graphics, boolean on) {
            if (on) {
                     //draw your own custom focus.
                    }
                }
        /**
         * Field implementation.
         * @see net.rim.device.api.ui.Field#layout(int, int)
         */
        protected void layout(int width, int height) {
            setExtent(Math.min( width, getPreferredWidth()),
            Math.min( height, getPreferredHeight()));
        }
        /**
         * Field implementation.
         * @see net.rim.device.api.ui.Field#paint(Graphics)
         */
        protected void paint(Graphics graphics){      
            // First draw the background colour and picture
            graphics.setColor(this.color);
            graphics.fillRect(0, 0, getWidth(), getHeight());
            graphics.drawBitmap(0, 0, getWidth(), getHeight(), _currentPicture, 0, 0);

            // Then draw the text
            graphics.setColor(Color.WHITE);
            graphics.setFont(_font);
            graphics.setFont(graphics.getFont().derive(Font.BOLD)); 
            graphics.drawText(_label, 5,9,
                (int)( getStyle() & DrawStyle.ELLIPSIS | DrawStyle.VALIGN_MASK | DrawStyle.HALIGN_MASK),
                getWidth() - 6 );

        }

        /**
         * Overridden so that the Event Dispatch thread can catch this event
         * instead of having it be caught here..
         * @see net.rim.device.api.ui.Field#navigationClick(int, int)
         */
        protected boolean navigationClick(int status, int time){
            fieldChangeNotify(1);
            return true;
        } 
}