Swing 将jpanel放在另一个类的jpanel之上

我试图使一个类中的Jpanel出现在另一个类中的Jpanel之上。我可以绕道而行，但我知道从长远来看我会后悔的。我的frame类包含带有按钮的主Jpanel，我想暂时将另一个带有按钮的Jpanel放在它上面。我试图简化我的代码。注意ShopButton方法和第一段代码下面的Shop类。这正是我想要关注的。我试图将Shop JPanel放在现有的“框架”（我称之为我的类）JPanel上

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public class Shop extends JPanel {
    public JButton CloseButton;
    public Shop(){
        CloseButton();
        setVisible(true);
        setLayout(null);
    }
    public void paint(Graphics g){
        System.out.println("shop is working");
        g.setColor(Color.WHITE);
        g.fillRect(100, 50, 350, 275);
        g.drawRect(100, 50, 350, 275);
    } 
    public void CloseButton(){
        //for 
        CloseButton= new JButton("Exit Shop");
        CloseButton.addActionListener( new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent Event) {
                System.out.println("am i alive?");
            }
        });
        CloseButton.setBounds(100, 100, 90, 30);
        add(CloseButton);
    }
}

---

覆盖

paintComponent（）

而不是

paint（）

，然后您可以正常放置组件并让swing负责绘制它们：

import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Graphics;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class Sample {
    private static class ImagePanel extends JPanel {
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            // Some background drawing
            g.setColor(Color.BLUE);
            g.fillOval(0, 0, getWidth(), getHeight());
        }
    }

    Sample() {
        JFrame frame = new JFrame("Button atop drawing");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationByPlatform(true);
        JPanel panel = new ImagePanel();
        panel.setLayout(new FlowLayout(FlowLayout.CENTER, 50, 50));

        JButton button = new JButton("Sample button");
        panel.add(button);

        frame.add(panel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Sample();
            }
        });
    }
}

。。。结果：

---

哇，我真不敢相信这会奏效。。。非常感谢你！我需要去检查油漆和油漆组件之间的区别，实际上现在它只添加了按钮，没有绘制我想要的填充矩形。我会设法找出原因。Thanks@CameronRoberson

paint（）

是顶级绘制方法，负责调用

paintComponent（）

、

paintChildren（）

和

paintBorder（）

。所以通常您只想覆盖

paintComponent（）

。如果您的子组件下面没有绘制某些内容，我的猜测是，要么它们不遵守不透明约定，要么在背景上绘制。对于按钮，您可以通过设置

button.setContentAreaFilled（false），快速检查它是否正在绘制；按钮。设置不透明（假）

并查看背景是否显示出来。

import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Graphics;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class Sample {
    private static class ImagePanel extends JPanel {
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            // Some background drawing
            g.setColor(Color.BLUE);
            g.fillOval(0, 0, getWidth(), getHeight());
        }
    }

    Sample() {
        JFrame frame = new JFrame("Button atop drawing");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationByPlatform(true);
        JPanel panel = new ImagePanel();
        panel.setLayout(new FlowLayout(FlowLayout.CENTER, 50, 50));

        JButton button = new JButton("Sample button");
        panel.add(button);

        frame.add(panel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Sample();
            }
        });
    }
}