如何突出（均匀视觉选择，绘制透明叠加）JPanel？

许多自定义Swing组件都是由JPanel 。 有时这些组件需要是可选择的。

怎样才能让JPanel看起来如此？ 它应该像其他项目一样被选择，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 /主题中的其他项目完全一样，

可能吗？

Answer 1

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

 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 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 { public static Map 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 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 getRenderingHints(JXLayer l) { return mapRenderHints; } public void repaint() { setDirty(true); } public void invalidate() { setDirty(true); } public void revalidate() { setDirty(true); } } }