Java Paint方法没有被调用

Question

I make a game in java and I can't seem to call the paintComponent() method in my game. here's the code :

public class TwinMoonTowers extends JPanel implements ActionListener{

    private class TMTMenu extends MouseAdapter{
        private Icon start, shop, quit;
        private Icon main_bg;

        public TMTMenu (){
            System.out.println("starting menu...");

            start = new Icon(TMTConstant.START_SOURCE,
                        TMTConstant.START_COORD_X, TMTConstant.START_COORD_Y);

            shop = new Icon (TMTConstant.SHOP_SOURCE,
                        TMTConstant.SHOP_COORD_X, TMTConstant.SHOP_COORD_Y);

            quit = new Icon (TMTConstant.EXIT_SOURCE,
                        TMTConstant.EXIT_COORD_X, TMTConstant.EXIT_COORD_Y);

            main_bg = new Icon (TMTConstant.MAIN_MENU_BG, 0, 0);
        }

        @Override
        public void mousePressed(MouseEvent me){

            int x = me.getX();
            int y = me.getY();

            System.out.println("coord: "+x+","+y);

            if (me.getButton() == MouseEvent.BUTTON1){
                if (x > start.x && x < start.x + start.getIcon().getWidth(null)
                        && y > start.y && y < start.y + start.getIcon().getHeight(null)){
                    curState = TMTConstant.MODE_STATE;
                }
                else if (x > quit.x && x < quit.x + quit.getIcon().getWidth(null)
                        && y > quit.y && y < quit.y + quit.getIcon().getHeight(null)){
                    curState = TMTConstant.EXIT_STATE;
                }
                else if (x > shop.x && x < shop.x + shop.getIcon().getWidth(null)
                        && y > shop.y && y < shop.y + shop.getIcon().getHeight(null)){
                    curState = TMTConstant.SHOP_STATE;
                }
            }

        }
    }

    private class TMTModeSelector extends MouseAdapter{
        private Icon TwinTower, TripleTower, back;

        public TMTModeSelector(){

        }

        @Override
        public void mousePressed(MouseEvent e){

        }
    }

    private String testDebug;
    private int curState;
    private TMTMenu menu;

    public TwinMoonTowers (){
        menu = new TMTMenu();
        curState = TMTConstant.MAIN_MENU_STATE;

        System.out.println("creating panel..");

        this.setVisible(true);
        this.setDoubleBuffered(true);
        this.setSize(TMTConstant.WINDOW_WIDTH, TMTConstant.WINDOW_HEIGHT);
        this.addMouseListener(menu);
    }

    @Override
    public void actionPerformed(ActionEvent arg0) {
        // TODO Auto-generated method stub
        this.repaint();

    }
    @Override
    public void paintComponent (Graphics g){
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;

        System.out.println("preparing canvas..");

        switch(curState){
            case TMTConstant.MAIN_MENU_STATE :
                g2d.drawImage(menu.main_bg.getIcon(), menu.main_bg.x, menu.main_bg.y, this);
                g2d.drawImage(menu.start.getIcon(), menu.start.x, menu.start.y, null);
                g2d.drawImage(menu.quit.getIcon(), menu.quit.x, menu.quit.y, null);
                g2d.drawImage(menu.shop.getIcon(), menu.shop.x, menu.shop.y, null);
                break;
            case TMTConstant.GAME_STATE :
                break;
            case TMTConstant.SHOP_STATE :
                break;
            case TMTConstant.MODE_STATE :
                break;
        }

        System.out.print("render image...");

        Toolkit.getDefaultToolkit().sync();
        g.dispose();

    }
}

while class Icon is this:

public class Icon{

private Image pic;
public int x, y;

public Icon (String path, int x, int y){

    ImageIcon ii = new ImageIcon (path);
    pic = ii.getImage();

    this.x = x;
    this.y = y;
}

public Image getIcon() {return pic;}
}

the basics here is to draw a menu containing 3 buttons (start, shop, exit)

but, the paintComponent method is not called (the system.out.println not showing)

Answer 1

Toolkit.getDefaultToolkit().sync();
g.dispose();

These lines are unnecessary (might even be wrong), remove them.

The problem is most likely not in the code you posted. Where do you add the panel to a top level window (frame/applet)? What layout do you use for its content pane? My guess is the size is (0,0) so the panel won't be painted.