如何突出（均匀视觉选择，绘制透明叠加）JPanel？

问题描述

许多自定义Swing组件由 JPanel 组成。有时这些组件是必需的。

Many custom Swing components are made of JPanel. Sometimes these components are required to be selectable.

如何才能使 JPanel 看起来如此？它应该像其他项目一样被选中，比如菜单项或 JTable 单元格。即整个 JPanel 应该用透明蓝色覆盖。这将是非常好的，如果这与L& F / theme中的其他项目完全一样，

How is it possible to make JPanel look selected? It should be selected like other items do, like menu items, or JTable cells. I.e. entire JPanel should be covered with transparent blue. It would be excellent, if this would made exactly like other items in L&F / theme,

是否可能？

推荐答案

您可以考虑查看 JXLayer / JLayer ，这将允许您在组件顶部绘制叠加层。

You could consider taking a look at JXLayer/JLayer, which would allow you to paint an overlay on top the component.

import java.awt.AlphaComposite;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.RenderingHints;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.Map;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import org.jdesktop.jxlayer.JXLayer;
import org.jdesktop.jxlayer.QualityHints;
import org.jdesktop.jxlayer.plaf.AbstractBufferedLayerUI;

public class Test {

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

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

                SelectablePane pane = new SelectablePane();
                SelectableUI ui = new SelectableUI();
                JXLayer<JPanel> layer = new JXLayer<>(pane, ui);
                layer.addMouseListener(new MouseAdapter() {

                    @Override
                    public void mouseClicked(MouseEvent e) {
                        ui.setSelected(!ui.isSelected());
                    }

                });

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(layer);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class SelectablePane extends JPanel {

        public SelectablePane() {

            setLayout(new GridBagLayout());
            add(new JLabel("Hello world"));

        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }
    }

    public static class SelectableUI extends AbstractBufferedLayerUI<JPanel> {

        public static Map<RenderingHints.Key, Object> mapRenderHints = new QualityHints();

        private boolean selected = false;

        public SelectableUI() {

            mapRenderHints.put(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY); // okay
            mapRenderHints.put(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); // bad
            mapRenderHints.put(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY); // okay
            mapRenderHints.put(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
            mapRenderHints.put(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
            mapRenderHints.put(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
            mapRenderHints.put(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);

        }

        public void setSelected(boolean value) {

            if (selected != value) {
                selected = value;
                firePropertyChange("selected", !selected, selected);
                repaint();
            }

        }

        public boolean isSelected() {
            return selected;
        }

        @Override
        protected void paintLayer(Graphics2D g2, JXLayer<? extends JPanel> l) {
            super.paintLayer(g2, l);
            if (isSelected()) {
                Graphics2D g2d = (Graphics2D) g2.create();
                g2d.setColor(UIManager.getColor("List.selectionBackground"));
                g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
                g2d.fillRect(0, 0, l.getWidth(), l.getHeight());
                g2d.dispose();
            }
        }

        @Override
        protected Map<RenderingHints.Key, Object> getRenderingHints(JXLayer<? extends JPanel> l) {
            return mapRenderHints;
        }

        public void repaint() {
            setDirty(true);
        }

        public void invalidate() {
            setDirty(true);
        }

        public void revalidate() {
            setDirty(true);
        }
    }

}

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