未修饰的JFrame阴影

Question

如何为未装饰的jframe添加阴影？

从我在网上找到的内容中，您也许可以将jframe添加到另一个黑色
半透明窗口中以产生阴影效果。或者以某种方式将
这样的内容应用于JFrame：

    Border loweredBorder = new EtchedBorder(EtchedBorder.LOWERED);
    setBorder(loweredBorder);

我只是想知道最好的方法，或者是完全不同的
方法来获得相同的效果，例如从另一个类而不是从
jframe扩展。我是Java的新手，所以我可能走错了方向，因此欢迎您提出任何
建议。

Answer 1

基本上，您需要制作一系列的图层。

• JFrame
• ShadowPanel

• and content…

  import java.awt.AlphaComposite;
  import java.awt.BorderLayout;
  import java.awt.Color;
  import java.awt.Dimension;
  import java.awt.EventQueue;
  import java.awt.Graphics;
  import java.awt.Graphics2D;
  import java.awt.GridBagLayout;
  import javax.swing.JFrame;
  import javax.swing.JLabel;
  import javax.swing.JPanel;
  import javax.swing.UIManager;
  import javax.swing.UnsupportedLookAndFeelException;
  import javax.swing.border.EmptyBorder;
  

  public class ShadowWindow {

  public static void main(String[] args) {
      new ShadowWindow();
  }
  
  public ShadowWindow() {
      EventQueue.invokeLater(new Runnable() {
          @Override
          public void run() {
              try {
                  UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
              } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
              }
  
              JFrame frame = new JFrame("Testing");
              frame.setUndecorated(true);
              frame.setBackground(new Color(0, 0, 0, 0));
              frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
              frame.setContentPane(new ShadowPane());
  
              JPanel panel = new JPanel(new GridBagLayout());
              panel.add(new JLabel("Look ma, no hands"));
  
              frame.add(panel);
              frame.pack();
              frame.setLocationRelativeTo(null);
              frame.setVisible(true);
          }
      });
  }
  
  public class ShadowPane extends JPanel {
  
      public ShadowPane() {
          setLayout(new BorderLayout());
          setOpaque(false);
          setBackground(Color.BLACK);
          setBorder(new EmptyBorder(0, 0, 10, 10));
      }
  
      @Override
      public Dimension getPreferredSize() {
          return new Dimension(200, 200);
      }
  
      @Override
      protected void paintComponent(Graphics g) {
          super.paintComponent(g);
          Graphics2D g2d = (Graphics2D) g.create();
          g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
          g2d.fillRect(10, 10, getWidth(), getHeight());
          g2d.dispose();
      }
  }
  

  }