java - 图形类似乎覆盖 JFrame/JPanel

Question

我在理解 JPanel、JFrame 和图形类的整个结构以及扩展和重写等方面遇到了一些困难。我似乎一切正常，直到我添加了图形类，然后 JPanel/JFrame 上的按钮等不再显示。我发现这与重写或 super 有关？但我确实需要一些澄清。非常感谢!

为了方便查看，我缩小了代码范围。

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.TitledBorder;

public class windowBuild extends JFrame {

    private static final long serialVersionUID = 1L;
    private JPanel contentPane;
    private int energy = 4;
    private JButton btnClaw = new JButton("Claw");
    private Image bg;
    private boolean loaded = false;

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                windowBuild frame = new windowBuild();
                frame.setVisible(true);

            }
        });
    }

    private class ButtonHandler implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            String which = e.getActionCommand();
            if (which.equals("Claw")) {
                energy = energy - 1;
                System.out
                        .println("Player one's dragon clawed the opponent. Dragon's energy is now at: "
                                + energy);
            }

        }

    }

    public void loadImage() {
        bg = new ImageIcon("C:\\res\\dragonDuelBackground.jpeg").getImage();
        loaded = true;
        repaint();
    }

    public windowBuild() {
        ButtonHandler bh;
        System.out.println("Starting frame...");
        bh = new ButtonHandler();
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 800, 600);
        contentPane = new JPanel();
        contentPane.setBorder(new TitledBorder(null, "Dragon Duel",
                TitledBorder.CENTER, TitledBorder.TOP, null, Color.CYAN));
        setContentPane(contentPane);
        contentPane.setLayout(null);

        btnClaw.setBounds(273, 511, 109, 39);
        contentPane.add(btnClaw);
        btnClaw.addActionListener(bh);

    }
//********************************************************************
//  public void paint(Graphics g) {
//      if (loaded) {
//          g.drawImage(bg, 400, 400, null);
//      }
//  }
//***************Uncomment this and the code won't work anymore**********
}

Answer 1

Uncomment this and the code won't work anymore

不要重写顶级容器(JFrame、JDialog...)的paint()。自定义绘制是通过重写 JPanel(或 JComponent)的 paintComponent() 方法来完成的。然后将面板添加到框架中。不要忘记调用 super.paintComponent(...)。

阅读 Custom Painting 上的 Swing 教程教程以获取更多信息和示例。