应用程序自动将宽度和高度增加 10 个像素

Question

My question is very wierd, after searching and reading the code 40 times, i can't explain why the jpanel and jframe gets additional 10 pixels to their width and height.

the code is:

public class Game extends JPanel implements Runnable {

        public static final String NAME = "ALPHA !";

        public static final int WIDTH = 600, HEIGHT = 400;

        public static void main(String[] args) {
            Game game = new Game();
            game.setMinimumSize(new Dimension(WIDTH, HEIGHT));
            game.setMaximumSize(new Dimension(WIDTH, HEIGHT));
            game.setPreferredSize(new Dimension(WIDTH, HEIGHT));
            game.setFocusable(true);
            game.requestFocusInWindow();

            JFrame frame = new JFrame(NAME);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

            frame.setLayout(new BorderLayout());
            frame.add(game, BorderLayout.CENTER);
            frame.pack();

            frame.setResizable(false);
            frame.setAlwaysOnTop(true);
            frame.setLocationRelativeTo(null);

            frame.setVisible(true);
            game.startGame();
        }

        public void startGame() {
            System.out.println("w " + getWidth() + ", h " + getHeight());
            new Thread(this).start();
        }
}

The println in the startGame method prints:

w 610, h 410

Thanks in advance.

Answer 1

使用frame.setUndecorated(true)那么你就会明白为什么高度和宽度增加了 10pxls。

Answer 2

I just encountered this problem when trying to add a single custom JPanel to my JFrame, which acts as a canvas. I'm using Java 8 (update 231) and this is still an issue happened.

I don't exactly know why this is happening. In the end, the issue could be fixed by calling the frame.setResizable(false) after frame.setVisible(true) on the JFrame.

Since I'm late to the party here, I hope this will help someone struggling with this as well.

Have a nice day

EDIT: Just saw the comments below the answer suggesting kind of the same by moving frame.setResizable(false) before frame.pack() , which works as well. Sorry for bringing this up again.. :)