JLayeredPane的典型实例

/**

*功能：实现面板的分层效果，而且小图标可以跟着鼠标移动

*/

import javax.swing.*;

import javax.swing.border.*;
import javax.accessibility.*;


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


/*
 * LayeredPaneDemo2.java requires
 * images/dukeWaveRed.gif.
*/
public class LayeredPaneDemo2 extends JPanel
                              implements ActionListener,
                                         MouseMotionListener {
    private String[] layerStrings = { "Yellow (0)", "Magenta (1)",
                                      "Cyan (2)",   "Red (3)",
                                      "Green (4)",  "Blue (5)" };
    private Color[] layerColors = { Color.yellow, Color.magenta,
                                    Color.cyan,   Color.red,
                                    Color.green,  Color.blue };


    private JLayeredPane layeredPane;
    private JLabel dukeLabel;
    private JCheckBox onTop;
    private JComboBox layerList;


    //Action commands
    private static String ON_TOP_COMMAND = "ontop";
    private static String LAYER_COMMAND = "layer";


    public LayeredPaneDemo2()    {
        setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS));


        //Create and load the duke icon.
        final ImageIcon icon = createImageIcon("images/dukeWaveRed.gif");


        //Create and set up the layered pane.
        layeredPane = new JLayeredPane();
        layeredPane.setPreferredSize(new Dimension(300, 310));
        layeredPane.setBorder(BorderFactory.createTitledBorder(
                                    "Move the Mouse to Move Duke"));
        layeredPane.addMouseMotionListener(this);


        //Add several labels to the layered pane.
        layeredPane.setLayout(new GridLayout(2,3));
        for (int i = 0; i < layerStrings.length; i++) {
            JLabel label = createColoredLabel(layerStrings[i],
                                              layerColors[i]);
            layeredPane.add(label, new Integer(i));
        }


        //Create and add the Duke label to the layered pane.
        dukeLabel = new JLabel(icon);
        if (icon == null) {
            System.err.println("Duke icon not found; using black rectangle instead.");
            dukeLabel.setOpaque(true);
            dukeLabel.setBackground(Color.BLACK);
        }
        layeredPane.add(dukeLabel, new Integer(2), 0);


        //Add control pane and layered pane to this JPanel.
        add(Box.createRigidArea(new Dimension(0, 10)));
        add(createControlPanel());
        add(Box.createRigidArea(new Dimension(0, 10)));
        add(layeredPane);
    }


    /** Returns an ImageIcon, or null if the path was invalid. */
    protected static ImageIcon createImageIcon(String path) {
        java.net.URL imgURL = LayeredPaneDemo2.class.getResource(path);
        if (imgURL != null) {
            return new ImageIcon(imgURL);
        } else {
            System.err.println("Couldn't find file: " + path);
            return null;
        }
    }


    //Create and set up a colored label.
    private JLabel createColoredLabel(String text,
                                      Color color) {
        JLabel label = new JLabel(text);
        label.setVerticalAlignment(JLabel.TOP);
        label.setHorizontalAlignment(JLabel.CENTER);
        label.setOpaque(true);
        label.setBackground(color);
        label.setForeground(Color.black);
        label.setBorder(BorderFactory.createLineBorder(Color.black));
        label.setPreferredSize(new Dimension(140, 140));
        return label;
    }


    //Create the control pane for the top of the frame.
    private JPanel createControlPanel() {
        onTop = new JCheckBox("Top Position in Layer");
        onTop.setSelected(true);
        onTop.setActionCommand(ON_TOP_COMMAND);
        onTop.addActionListener(this);


        layerList = new JComboBox(layerStrings);
        layerList.setSelectedIndex(2);    //cyan layer
        layerList.setActionCommand(LAYER_COMMAND);
        layerList.addActionListener(this);


        JPanel controls = new JPanel();
        controls.add(layerList);
        controls.add(onTop);
        controls.setBorder(BorderFactory.createTitledBorder(
                                 "Choose Duke's Layer and Position"));
        return controls;
    }


    //Make Duke follow the cursor.
    public void mouseMoved(MouseEvent e) {
        dukeLabel.setLocation(e.getX()-dukeLabel.getWidth()/2,
                              e.getY()-dukeLabel.getHeight()/2);
    }
    public void mouseDragged(MouseEvent e) {} //do nothing


    //Handle user interaction with the check box and combo box.
    public void actionPerformed(ActionEvent e) {
        String cmd = e.getActionCommand();


        if (ON_TOP_COMMAND.equals(cmd)) {
            if (onTop.isSelected())
                layeredPane.moveToFront(dukeLabel);
            else
                layeredPane.moveToBack(dukeLabel);


        } else if (LAYER_COMMAND.equals(cmd)) {
            int position = onTop.isSelected() ? 0 : 1;
            layeredPane.setLayer(dukeLabel,
                                 layerList.getSelectedIndex(),
                                 position);
        }
    }


    /**
     * 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("LayeredPaneDemo2");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


        //Create and set up the content pane.
        JComponent newContentPane = new LayeredPaneDemo2();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);


        //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();
            }
        });
    }
}