如何使JPanel更透明，更透明，最终消失？

1 回答

• 3

  因为 BallonPanel 是不透明的，所以重绘管理器不需要绘制 .

  您需要“说服”重绘管理器在组件下方绘制，同时仍然绘制其背景 .

  将 BallonPanel 设置为透明（ setOpaque(false) ）并更新 paint 方法以填充背景 .

  public class FadePane {
  
      public static void main(String[] args) {
          new FadePane();
      }
  
      public FadePane() {
          EventQueue.invokeLater(new Runnable() {
              @Override
              public void run() {
                  try {
                      UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                  } catch (Exception ex) {
                  }
  
                  JFrame frame = new JFrame("Test");
                  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                  frame.getContentPane().setBackground(Color.BLUE);
                  frame.setBackground(Color.BLUE);
                  frame.add(new BaloonPanel());
                  frame.pack();
                  frame.setLocationRelativeTo(null);
                  frame.setVisible(true);
  
              }
          });
      }
  
      public class BaloonPanel extends JPanel {
  
          private float transparency = 1f;
          Timer timer;
  
          public BaloonPanel() {
  
              setBackground(Color.white);
              ActionListener action = new ActionListener() {
                  @Override
                  public void actionPerformed(ActionEvent e) {
                      transparency = transparency - 0.1f;
  
                      if (transparency < 0.1f) {
                          transparency = 0;
                          timer.stop();
                      }
                      invalidate();
                      repaint();
                  }
              };
  
              timer = new Timer(100, action);
              timer.setRepeats(true);
  
              setOpaque(false);
  
              final JButton fade = new JButton("Fade");
              fade.addActionListener(new ActionListener() {
                  @Override
                  public void actionPerformed(ActionEvent e) {
                      timer.start();
                      fade.setEnabled(false);
                  }
              });
  
              setLayout(new GridBagLayout());
              add(fade);
          }
  
          @Override
          public void paint(Graphics g) {
              Graphics2D g2 = (Graphics2D) g.create();
              System.out.println(transparency);
              g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, transparency));
              g2.setColor(getBackground());
              g2.fillRect(0, 0, getWidth(), getHeight());
              super.paint(g2);
              g2.dispose();
          }
      }
  }
  

  回复于 2024-04-20T01:29:29+08:00