调整JFrame的大小以适应调整后的JPanel

Question

我对JPanel和JFrame还是个新手，可能没有按照我应该的方式使用它们。我正在尝试创建Pong游戏，在创建JFrame并将JPanel添加到它之后，我可以调整JPanel的大小，但我不知道如何调整JFrame的大小以适应它。Game类扩展了JPanel。

主：

    public static void main(String[] args) throws InterruptedException {
        int height = 500, width =(int) (height*1.56); //height = 500, width = 780;
        JFrame frame = new JFrame("Pong");
        Game game = new Game();
        frame.add(game);
        frame.setVisible(true);
        game.setSize(width, height);
        System.out.println(game.getHeight());
        System.out.println(game.getWidth());
        game.setBackground(Color.BLACK);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        System.out.println(frame.getHeight());
        System.out.println(frame.getWidth());
    }

500
780
39
136

500
780
*above* 500
*above* 780

编辑：

    public static void main(String[] args) throws InterruptedException {
        int height = 500, width =(int) (height*1.56); //height = 500, width = 780;
        JFrame frame = new JFrame("Pong");
        Game game = new Game();
        frame.add(game);
        frame.setVisible(true);
        game.setPreferredSize(new Dimension(width, height));
        frame.pack();
        System.out.println(game.getHeight());
        System.out.println(game.getWidth());
        game.setBackground(Color.BLACK);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        System.out.println(frame.getHeight());
        System.out.println(frame.getWidth());
    }

将setSize更改为setPreferredSize，然后为JFrame调用pack（）就可以解决所有问题。

Answer 1

同样，处理首选的大小，并确保在添加组件后在您的JFrame上调用pack()。此外，重写getPreferredSize比调用setPreferredSize更好。例如：

import java.awt.Dimension;
import javax.swing.*;

public class Game extends JPanel {
    private static final int PREF_W = 400;
    private static final int PREF_H = 300;
    private int prefW;
    private int prefH;

    public Game(int prefW, int prefH) {
        this.prefW = prefW;
        this.prefH = prefH;
    }

    public Game() {
        this(PREF_W, PREF_H);
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet()) {
            return super.getPreferredSize();
        }
        return new Dimension(prefW, prefH);
    }

    private static void createAndShowGui() {
        int height = 500; 
        int width =(int) (height*1.56); //height = 500, width = 780;

        Game game = new Game(width, height);

        JFrame frame = new JFrame("Game");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(game);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);

        System.out.println("Frame size: " + frame.getSize());
        System.out.println("game size: " + game.getSize());
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }
}