使用GridLayout制作JList

Question

I needed a JList to contain a JPanel , however, this is not possible, so I am making a replica via the use of GridLyayout . It works fine, however, I would want an 'absolute' dimension set to all the grids, or at least have it so only 10 are visible on the screen and the rest are below, since the container is a scroll pane. Just to clarify, the grid layout has 1 row, and 0 (or x) columns.

Anyone have any idea?

Answer 1

I needed a JList to contain a JPanel , however, this is not possible

Of course it is possible. The secret to getting them to look nice is in the rendering.

import java.awt.*;
import java.util.Vector;
import javax.swing.*;

class PanelsInList {

    JPanel ui = null;
    Color[] colors = {
        Color.RED, Color.GREEN, Color.BLUE,
        Color.MAGENTA, Color.PINK, Color.YELLOW,
        Color.BLACK, Color.GRAY, Color.WHITE 
    };

    PanelsInList() {
        initUi();
    }

    public final void initUi() {
        if (ui != null) {
            return;
        }
        ui = new JPanel(new BorderLayout());

        Vector<JPanel> listContent = new Vector<JPanel>();
        for (int ii=1; ii<colors.length+1; ii++) {
            Color c = colors[(ii-1)%colors.length];
            listContent.add(getPanel(c,ii));
        }
        JList<JPanel> list = new JList<JPanel>(listContent);
        // the secret to getting them to look nice is in the rendering
        list.setCellRenderer(new PanelCellRenderer());
        list.setVisibleRowCount(3);
        ui.add(new JScrollPane(list));
    }

    class PanelCellRenderer extends DefaultListCellRenderer {

        @Override
        public Component getListCellRendererComponent(
                JList list, 
                Object value, 
                int index, 
                boolean isSelected, 
                boolean cellHasFocus) {
            Component c = super.getListCellRendererComponent(
                    list, value, index, isSelected, cellHasFocus);
            JPanel p = null;
            if (value instanceof JPanel && c instanceof JLabel) {
                 p = (JPanel)value;
                 JLabel l = (JLabel)c;
                 p.setBackground(l.getBackground());
                 p.setForeground(l.getForeground());
                 p.setBorder(l.getBorder());
            }
            return p;
        }
    }

    public JPanel getPanel(Color color, int n) {
        JPanel p = new JPanel(new GridLayout());

        JLabel l = new JLabel(
                "Label " + n, new ColoredIcon(color), SwingConstants.LEADING);
        p.add(l);

        return p;
    }

    class ColoredIcon implements Icon {

        int sz = 16;
        Color color;

        ColoredIcon(Color color) {
            this.color = color;
        }

        @Override
        public void paintIcon(Component c, Graphics g, int x, int y) {
            g.setColor(color);
            g.fillRect(0, 0, sz, sz);
        }

        @Override
        public int getIconWidth() {
            return sz;
        }

        @Override
        public int getIconHeight() {
            return sz;
        }

    }

    public JComponent getUi() {
        return ui;
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {

            @Override
            public void run() {
                PanelsInList pil = new PanelsInList();

                JOptionPane.showMessageDialog(null, pil.getUi());
            }
        };
        // Swing GUIs should be created and updated on the EDT
        // http://docs.oracle.com/javase/tutorial/uiswing/concurrency
        SwingUtilities.invokeLater(r);
    }
}