Newbie JLayeredPane问题

Question

package components;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

/* FrameDemo.java requires no other files. */
public class FrameDemo {
    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("FrameDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel mainLayer = new JPanel(new BorderLayout());
        mainLayer.setPreferredSize(new Dimension(640, 480));
        frame.setContentPane(mainLayer);
        frame.getLayeredPane().add(mainLayer, JLayeredPane.DEFAULT_LAYER, 0);

        JLabel emptyLabel = new JLabel("LABEL");
        emptyLabel.setPreferredSize(new Dimension(320, 240));
        mainLayer.add(emptyLabel, BorderLayout.NORTH);

        JPanel subLayer = new JPanel(new BorderLayout());
        JLabel subLabel = new JLabel("SUBLABEL");
        subLabel.setPreferredSize(new Dimension( 200, 100));
        subLabel.setBackground(Color.YELLOW);
        subLayer.add(subLabel, BorderLayout.SOUTH);
        subLayer.setVisible(true);
        subLabel.setVisible(true);
        frame.getLayeredPane().add(subLayer, JLayeredPane.PALETTE_LAYER, 0);


        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

//        frame.setContentPane(mainLayer);

增编：

下面的代码说明了我想要实现的功能，它与下面的TrashGod设置的功能非常相似，并且能够正常工作。有一个具有常量层（在整数（0）处分层）和浮动层的JLayeredPane，浮动层最初在整数（-1）处分层，但可以通过在整数（-1）层和整数（1）层之间的F7和F8键切换，从而允许它浮动在常量层之上或之下。

package components;

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;


/* MyLayeredPaneDemo.java requires no other files. */
public class MyLayeredPaneDemo {
    private JFrame frame;
    private JLayeredPane mainPanel;
    private JPanel constantLayer;
    private JPanel floatingLayer;
    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private MyLayeredPaneDemo() {}
    private void createAndShowGUI() {
        //Create and set up the window.
        this.frame = new JFrame("MyLayeredPaneDemo");
        this.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.frame.setPreferredSize(new Dimension(640, 480));
        mainPanel = new JLayeredPane();
        constantLayer = new JPanel(new BorderLayout(0,0));
        floatingLayer = new JPanel(new BorderLayout(0,0));
//        constantLayer.setPreferredSize();
        constantLayer.setOpaque(true);
        constantLayer.setBackground(Color.BLUE);


        JLabel constantLabel = new JLabel("MAIN LAYER");
        constantLayer.setPreferredSize(new Dimension(640, 480));
        constantLayer.add(constantLabel, BorderLayout.CENTER);

        JLabel subLabel = new JLabel("SUB LAYER");
        floatingLayer.setBackground(Color.YELLOW);
        floatingLayer.add(subLabel, BorderLayout.SOUTH);
        floatingLayer.setOpaque(true);
        floatingLayer.setVisible(true);
        floatingLayer.setVisible(true);
        subLabel.setBackground(Color.YELLOW);

        mainPanel.add(constantLayer, new Integer(0), 0);
        constantLayer.setBounds(0,0,640,480);
        mainPanel.add(floatingLayer, new Integer(-1), 0);
        floatingLayer.setBounds(100, 360, 300, 90 );

        frame.add(mainPanel, BorderLayout.CENTER);

        //Display the window.
        mapKeyToAction(frame.getRootPane(), 
                JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT,
                KeyStroke.getKeyStroke(KeyEvent.VK_F7, 0),
                "Hide Layer", 
                new AbstractAction() {

                    @Override
                    public void actionPerformed(ActionEvent e) {
                        System.out.println("F7 pressed");
                        mainPanel.setLayer(floatingLayer, new Integer(-1));
                    }       
                }); 
        mapKeyToAction(frame.getRootPane(), 
                JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT,
                KeyStroke.getKeyStroke(KeyEvent.VK_F8, 0),
                "Show Layer", 
                new AbstractAction() {

                    @Override
                    public void actionPerformed(ActionEvent e) {
                        System.out.println("F8 pressed");
                        mainPanel.setLayer(floatingLayer, new Integer(1));
                    }       
                }); 
        frame.pack();
        frame.setVisible(true);
        frame.getRootPane().setFocusable(true);
        boolean ok = frame.getRootPane().requestFocusInWindow();
        System.out.println("focus ok: " + ok);

    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new MyLayeredPaneDemo().createAndShowGUI();
            }
        });
    }

    private static void mapKeyToAction(JComponent component, 
            int whichMap, KeyStroke keystroke,String key, Action action) {
        component.getInputMap(whichMap).put(keystroke, key);
        component.getActionMap().put(key, action);
    }

}

然而，我很难让这个在我的真实情况下工作。两者之间的区别在于，在这里，我的JLayeredPane由框架拥有，而在我的实际应用程序中，我希望JLayeredPane由JPanel拥有，因为它位于框架的包含层次结构中的某些级别，其大小由其父级中的GridBagLoyout设置，因此在调用其构造函数时，大小是不可知的，这使得调用setBounds（）变得困难，而我需要在JLayeredPane的子级上调用setBounds（）。

进一步增编。我知道Oracle教程中提到了一种情况，即在JLayeredPane中使用布局而不是绝对定位。这个例子和我的不同之处在于，在我的例子中，层在不同的层上占据相同的水平空间，而在这个例子中，不同层上的组件占据不同的水平空间。它几乎就像我们需要一个3D布局管理器！

Answer 1

“默认情况下，分层窗格没有布局管理器。”-如何使用分层窗格

补充：我需要避免使用框架的分层窗格，而是在窗口中添加一个分层窗格。

是的，根窗格是jrootpane的实例，它包含jlayeredpane。特别是，“分层窗格包含菜单栏和内容窗格，并支持其他组件的Z排序。”

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class FrameDemo {

    private static void createAndShowGUI() {
        JFrame frame = new JFrame("FrameDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JLayeredPane mainLayer = new JLayeredPane();
        frame.add(mainLayer, BorderLayout.CENTER);

        JLabel label = new JLabel("LABEL", JLabel.CENTER);
        label.setBounds(100, 100, 200, 100);
        label.setOpaque(true);
        label.setBackground(Color.cyan);
        mainLayer.add(label, 1);

        JPanel subLayer = new JPanel(new BorderLayout());
        JLabel subLabel = new JLabel("SUBLABEL", JLabel.CENTER);
        subLabel.setBounds(20, 20, 200, 100);
        subLabel.setOpaque(true);
        subLabel.setBackground(Color.yellow);
        subLayer.add(subLabel, BorderLayout.SOUTH);
        mainLayer.add(subLabel, 2);

        frame.pack();
        frame.setSize(320, 240);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                createAndShowGUI();
            }
        });
    }
}