JButton 被图像覆盖

Question

我正在尝试为棋盘游戏风险制作一个主菜单。有一个自定义背景图像，理想情况下我希望按钮显示在图像上。但是，当我运行我的代码时，只会出现名为 "New Game" 的按钮，如果将鼠标悬停在其他按钮上，它们就会出现。我已经尝试了几乎所有的方法（这里也有类似的问题）但似乎无法解决问题。也许它与我的代码有关？我很感激任何 help/suggestions!

package View;


import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Image;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JButton;
import javax.swing.SpringLayout;

/**
* These classes set up the GUI of the Risk program.
* The main menu, dialog for setting player count, dialog for name/color       settings for each 
 * player, the Risk game board, and a menu used during a Risk game session are    included.

 **/
public class Menu extends JFrame {  

    private JPanel mainPanel;


    private JButton newGameButton;
    private JButton loadGameButton;
    private JButton quitButton;
    private JButton ruleButton;

    private String newGameButtonName = "newGameBtn";
    private String loadGameButtonName = "loadGameBtn";
    private String quitButtonName = "quitBtn";
    private String ruleButtonName = "rulebtn";

    //private SpringLayout mainLayout;
     private static BufferedImage img;

    /**
     * Constructs the main menu.
     **/
    public Menu() 
    {
        add( mainMenu( ) );
        //setTitle("Risk: UConn Edition");
        setPreferredSize(new Dimension(640, 700));
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        setResizable(false);



        toFront();
        pack();

        setVisible(true);


    }

    /**
     * creates the buttons for the jPanel
     * 
     * @return
     */
    private JPanel mainMenu()
    {
        // Creates the panel
        mainPanel = new JPanel();
        // Sets Layout
        //mainLayout = new SpringLayout();
       mainPanel.setLayout(null);

        // Creates buttons
        newGameButton = new JButton("New Game");
        newGameButton.setBounds(20,300,150,50);
        newGameButton.setOpaque(false);
        newGameButton.setContentAreaFilled(false);
        newGameButton.setForeground(Color.RED);
        newGameButton.setBackground(Color.BLUE);

        loadGameButton = new JButton("Load Game");
        loadGameButton.setBounds(20,400,150,50);
        //loadGameButton.setOpaque(false);
        //loadGameButton.setContentAreaFilled(false);
        loadGameButton.setForeground(Color.RED);

        quitButton = new JButton("Quit");
        quitButton.setBounds(490,400,150,50);
        quitButton.setOpaque(false);
        quitButton.setContentAreaFilled(false);
        quitButton.setForeground(Color.RED);

        ruleButton = new JButton("Rules");
        ruleButton.setBounds(490,300,150,50);
        ruleButton.setOpaque(false);
        ruleButton.setContentAreaFilled(false);
        ruleButton.setForeground(Color.RED);

        // Sets button commands
        newGameButton.setActionCommand(newGameButtonName);
        loadGameButton.setActionCommand(loadGameButtonName);
        quitButton.setActionCommand(quitButtonName);

        // Adds buttons to mainPanel
        mainPanel.add(newGameButton);
        mainPanel.add(loadGameButton);
        mainPanel.add(quitButton);
        mainPanel.add(ruleButton);
    //  add(mainPanel);

        return mainPanel;
    }
    private Image createImage(){
        try {
            img = ImageIO.read(
                    Menu.class.getResource("../resource/riskUconn.jpg"));


        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return img;
      }
    /**
     * paint method
     */
    @Override
    public void paint (Graphics g)  {

        Image img = createImage();
        g.drawImage(img, 20,20,this);
        super.paint(g);


      }


    // Action listeners for Menu
    protected void riskViewActionListeners(ActionListener evt)
    {
        newGameButton.addActionListener(evt);
        loadGameButton.addActionListener(evt);
        quitButton.addActionListener(evt);
    }



    public static void main(String [] args){
        Menu m = new Menu();


    }
}

Answer 1

绘制组件并不总是通知父组件或子组件。不要覆盖 paint，而是尝试覆盖 paintComponent 并在那里绘制背景，这就是 paintComponent 的真正含义，绘制背景。

您应该避免覆盖 paint 顶级容器。
大多数顶层容器都有一系列层，包括 JRootPane、contentPane 甚至 glassPane，所有这些层都将绘制在框架的顶部。

相反，创建一个自定义组件，它从 JPanel 之类的东西扩展而来，并将其用作您的基础组件。您可以覆盖它的 paintComponent 并在其中绘制背景。然后将此组件添加到您的框架中，甚至可能使其成为内容窗格。

记住，如果一个组件是不透明的，它将覆盖任何子组件

您还应该避免从任何绘制方法中加载资源（尤其是连续重新加载它们），因为这会对您的程序性能产生影响。画画要越快越好

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