如何在JList中的JLayeredPane中单击按钮

Question

I have a button in a JLayeredPane in a JList so I can overlay icon buttons on each row on mouse over. However, the buttons are not accepting mouse clicks. The code is below. Nothing is output when clicking on anything. If I add a mouse listener to the JList, that will be called.

import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.FontMetrics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.DefaultListCellRenderer;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JLayeredPane;
import javax.swing.JList;
import javax.swing.SwingConstants;
import javax.swing.border.LineBorder;


public class TestListLayered
{
    public static class LayeredListCellRenderer extends DefaultListCellRenderer
    {
        @Override
        public Component getListCellRendererComponent(final JList list, final Object value, final int index,
                final boolean isSelected, final boolean cellHasFocus)
        {
            final JLayeredPane pane = new JLayeredPane();
            final JLabel label = (JLabel) super.getListCellRendererComponent(list, value.toString(), index, isSelected,
                    cellHasFocus);
            label.setHorizontalAlignment(SwingConstants.RIGHT);
            label.setBounds(0, 0, 100, 20);
            pane.add(label, JLayeredPane.DEFAULT_LAYER);

            final JButton edit = new JButton("e");
            final FontMetrics fontMetrics = edit.getFontMetrics(edit.getFont());
            final int height2 = (int) (1.5 * fontMetrics.getHeight());
            edit.setBounds(0, 0, (int) (1.5 * fontMetrics.stringWidth("e")), height2);
            edit.addActionListener(new ActionListener()
            {
                @Override
                public void actionPerformed(final ActionEvent e)
                {
                    System.out.println("button");
                }
            });
            pane.addMouseListener(new MouseAdapter()
            {
                @Override
                public void mouseClicked(final MouseEvent e)
                {
                    System.out.println("layeredpane");
                }
            });
            pane.add(edit, JLayeredPane.PALETTE_LAYER);

            pane.setPreferredSize(new Dimension(-1, height2));
            pane.setBorder(new LineBorder(Color.blue));
            return pane;
        }
    }

    public static void main(final String[] args)
    {
        final JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        final JList<String> l = new JList<String>(new String[] { "item 1", "item 2" });
        l.setCellRenderer(new LayeredListCellRenderer());
        f.add(l);

        f.pack();
        f.setVisible(true);
    }
}

Answer 1

A renderer is not a real component. It is just a painting of a component. So the button will not respond to clicks.

Not sure I understand what you are trying to do, but maybe you can use a two column JTable. Because a table supports an editor it does respond to mouse clicks. Table Button Column can help you here.

Answer 2

First, I just want to say, this is very weird...

Basically, you should add a MouseListener to the JList . When it's clicked, you need to find the cell bounds of the selected row, convert the mouse point into a local context for the cell renderer and then test to see if the mouse clicked within the bounds of the button...

What you do after that is up to you.

import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.DefaultListCellRenderer;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JLayeredPane;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.SwingConstants;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.LineBorder;

public class TestListLayered {

    public static class LayeredListCellRenderer extends DefaultListCellRenderer {

        private JButton edit = new JButton("e");

        @Override
        public Component getListCellRendererComponent(final JList list, final Object value, final int index,
                final boolean isSelected, final boolean cellHasFocus) {
            final JLayeredPane pane = new JLayeredPane();
            final JLabel label = (JLabel) super.getListCellRendererComponent(list, value.toString(), index, isSelected,
                    cellHasFocus);
            label.setHorizontalAlignment(SwingConstants.RIGHT);
            label.setBounds(0, 0, 100, 20);
            pane.add(label, JLayeredPane.DEFAULT_LAYER);

            final FontMetrics fontMetrics = edit.getFontMetrics(edit.getFont());
            final int height2 = (int) (1.5 * fontMetrics.getHeight());
            edit.setBounds(0, 0, (int) (1.5 * fontMetrics.stringWidth("e")), height2);
            pane.add(edit, JLayeredPane.PALETTE_LAYER);

            pane.setPreferredSize(new Dimension(-1, height2));
            pane.setBorder(new LineBorder(Color.blue));
            return pane;
        }

        protected void buttonClicked(Point p) {
            System.out.println(edit.contains(p));
        }
    }

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

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

                final JFrame f = new JFrame();
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

                final JList<String> l = new JList<String>(new String[]{"item 1", "item 2"});
                l.setCellRenderer(new LayeredListCellRenderer());
                f.add(new JScrollPane(l));

                l.addMouseListener(new MouseAdapter() {
                    @Override
                    public void mouseClicked(MouseEvent e) {
                        int index = l.locationToIndex(e.getPoint());
                        if (index > -1) {

                            Rectangle bounds = l.getCellBounds(index, index);
                            LayeredListCellRenderer cellRenderer = (LayeredListCellRenderer) l.getCellRenderer();
                            Component renderComp = cellRenderer.getListCellRendererComponent(l, l.getModel().getElementAt(index), index, false, false);
                            renderComp.setBounds(bounds);

                            Point local = new Point(e.getPoint());
                            local.x -= bounds.x;
                            local.y -= bounds.y;

                            cellRenderer.buttonClicked(local);

                        }
                    }
                });

                f.pack();
                f.setVisible(true);
            }
        });
    }
}

I'd just like to say, I agree with camickr, it would be better to use a 2 column JTable ...