如何仅显示不可见 jframe 或 jpanel 的按钮？

Question

下面的示例将显示一个带有 jframe 窗口的按钮。我只想要按钮可见，怎么实现？

public final void initUI() {

  JPanel panel = new JPanel();
  getContentPane().add(panel);

  panel.setLayout(null);

  JButton quitButton = new JButton("Quit");
   quitButton.setBounds(50, 60, 80, 30);
   quitButton.addActionListener(new ActionListener() {
       public void actionPerformed(ActionEvent event) {
           System.exit(0);
      }
   });

   panel.add(quitButton);

   setTitle("Quit button");
   setSize(300, 200);
   setLocationRelativeTo(null);
   setDefaultCloseOperation(EXIT_ON_CLOSE);
}

Answer 1

根据你的意思，“没有 jframe 或 jpanel 可见？” 你创建一个透明窗口...

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class GhostButton {

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

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

                JButton ghostButton = new JButton("Boo!");
                ghostButton.addActionListener(new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        System.exit(0);
                    }
                });

                JFrame frame = new JFrame("Testing");
                frame.setUndecorated(true);
                frame.setBackground(new Color(0,0,0,0));
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(ghostButton);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

}

如果你删除frame.setBackground(new Color(0,0,0,0));，你会得到一个无框窗口

ps- 这在 Java 7+ 下工作，有技巧让它在 Java 6 下工作，但我没有在这里发布