问双缓冲a JFrame

EN

public class MainWindow extends JFrame implements KeyListener{
private Dimension dim;
private CardLayout layout;
private JPanel panel;
private JLayeredPane gameLayers;
private Menu menu;
private MiniGame miniGame;
private Board board;
private Sprite sprite;
private Game game;
private Map map;
private GameState gs;

private Boolean[] keys;


public MainWindow(Game game, GameState gs, Map map, Sprite sprite){
    //Call superclass.
    super();

    addKeyListener(this);

    //Sore references to critical game components.
    this.game = game;//So we can call methods when an event occurs.
    this.gs = gs;
    this.map = map;//Used to construct the board.
                    //The board needs to know the layout of the map.
    this.sprite = sprite;//Used to add the sprite to one of the layers.

    //Instantiate objects.
    dim = new Dimension(800, 600);
    layout = new CardLayout();
    panel = new JPanel(layout);
    menu = new Menu();
    miniGame = new MiniGame();
    board = new Board(map);
    gameLayers = new JLayeredPane();

    //Remove decoration and place window in center of screen.
    setUndecorated(true);
    Dimension screenDim = Toolkit.getDefaultToolkit().getScreenSize();
    setBounds((screenDim.width /2)-(dim.width/2),
            (screenDim.height/2)-(dim.height/2),
            dim.width,
            dim.height);

    //Add the board to a layer.
    gameLayers.add(board, JLayeredPane.DEFAULT_LAYER);
    board.setBounds(0, 0, dim.width, dim.height);
    board.setBoard();

    //Add the sprite to a layer.
    gameLayers.add(sprite, JLayeredPane.PALETTE_LAYER);
    sprite.setBounds(0, 0, 50, 50);

    //Add components to window.
    panel.add(gameLayers, "gameLayers");
    panel.add(miniGame, "miniGame");
    panel.add(menu, "menu");

    //Add the "cards" to the window.
    add(panel);

    //JFrame housekeeping.
    pack();
    setSize(dim);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setResizable(false);
    setVisible(true);

    //Holds state when an event is triggered.
    //Ugly hack to circumvent delay issue.
    keys = new Boolean[4];
    for(int i=0; i<keys.length; i++){
        keys[i] = false;
    }
}
}