Java Awt 和 Swing

Question

Pong.Java

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JFrame;

public class Pong {
    private static final int WIDTH = 900, HEIGHT = 700;
    JFrame win = new JFrame();
    Paddle paddleOne = new Paddle(1);
    Paddle paddleTwo = new Paddle(2);
    Graphics g;

    Pong(){
        init();
    }

    void init(){
        win.setTitle("PONG");
        win.setSize(WIDTH, HEIGHT);
        win.addKeyListener(keyListener);
        win.setLocationRelativeTo(null);
        win.getContentPane().setBackground(Color.black);
        win.setVisible(true);
        win.getContentPane().validate();
        win.repaint();
    }


    public void paintComponent(Graphics g){
        g.setColor(Color.white);
        g.fillRect(paddleOne.getX(), paddleOne.getY(), paddleOne.getHEIGHT(), paddleOne.getWIDTH());

        System.out.println("drawn");
    }

    KeyListener keyListener = new KeyListener() {
        public void keyPressed(KeyEvent e) {
            int key = e.getKeyCode();

            switch(key){
            case 87:
                System.out.println("Player 1 Up");
                break;
            case 83:
                System.out.println("Player 1 Down");
                break;
            case 38:
                System.out.println("Player 2 Up");
                break;
            case 40:
                System.out.println("Player 2 Down");
                break;
            }

            win.getContentPane().validate();
            win.repaint();

        }

        public void keyReleased(KeyEvent arg0) {
            // TODO Auto-generated method stub

        }

        public void keyTyped(KeyEvent arg0) {
            // TODO Auto-generated method stub

        }

    };

    public static void main(String[] args) {
        Pong p = new Pong();
    }
}

Paddle.Java

public class Paddle{
private int WIDTH = 50, HEIGHT = 150, X, Y;


int playerNum;

Paddle(int playerNum){
    if(playerNum == 1){
        X = 10;
        Y = 10;
    }else if (playerNum == 2){
        X = 500;
        Y = 10;
    }
}

public void setX(int x){
    X = x;
}

public void setY(int y){
    Y = y;
}

public int getWIDTH() {
    return WIDTH;
}

public int getHEIGHT() {
    return HEIGHT;
}

public int getX() {
    return X;
}

public int getY() {
    return Y;
}

}

我对 Java 编程，或者更具体地说，Awt 和 Swing 比较陌生，我的问题是，为什么我的矩形没有绘制？任何帮助表示赞赏。非常感谢!

Answer 1

为了在 Swing 中绘制某些内容，它首先必须从 Swing 知道如何绘制的内容扩展，这通常意味着 JComponent (或更典型的是 JPanel )。

然后你可以重写其中一个绘画方法，该方法由绘画子系统调用，在这种情况下，通常首选重写 paintComponent ，但别忘了调用super.paintComponent在进行任何自定义绘画之前，或者您正在为自己设置一些奇怪且通常不可预测的绘画问题。

看看Painting in AWT and Swing和 Performing Custom Painting了解更多详情。

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Pongo {

    public static void main(String[] args) {
        new Pongo();
    }

    public Pongo() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new PongPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class PongPane extends JPanel {

        private static final int WIDTH = 900, HEIGHT = 700;
        Paddle paddleOne = new Paddle(1);
        Paddle paddleTwo = new Paddle(2);

        public PongPane() {
            setBackground(Color.BLACK);
        }

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.setColor(Color.white);
            g.fillRect(paddleOne.getX(), paddleOne.getY(), paddleOne.getHEIGHT(), paddleOne.getWIDTH());

            //System.out.println("drawn");   //Should not put something here which may overhead.
        }

    }

    public class Paddle {

        private int WIDTH = 50, HEIGHT = 150, X, Y;

        int playerNum;

        Paddle(int playerNum) {
            if (playerNum == 1) {
                X = 10;
                Y = 10;
            } else if (playerNum == 2) {
                X = 500;
                Y = 10;
            }
        }

        public void setX(int x) {
            X = x;
        }

        public void setY(int y) {
            Y = y;
        }

        public int getWIDTH() {
            return WIDTH;
        }

        public int getHEIGHT() {
            return HEIGHT;
        }

        public int getX() {
            return X;
        }

        public int getY() {
            return Y;
        }
    }
}

我也不鼓励使用 KeyListener在此上下文和内部建议中使用键绑定(bind) API，它不会遇到 KeyListener 相同的焦点相关问题。做。请参阅How to Use Key Bindings了解更多详情