Java Swing - 将透明度应用于透明JPanel上的组件

1 回答

• 3

  我找到了一个解决方案 - 基本上我在评论中已经提到过：面板并没有真正画在屏幕上 . 而是将其绘制成图像，并使用适当的 AlphaComposite 绘制此图像 .

  

  （滑块可用于设置面板的不透明度）

  虽然这个解决方案很简单，通用，并且应该基本上适用于所有子组件，但是有类似的地方：调整 RepaintManager 的必要性 . 为了确保应用面板的不透明度（并且子组件未独立绘制，并且具有完全不透明度），重绘管理器必须在重新绘制子组件时触发整个组件的重绘 . 我认为应该有没有这种解决方法的解决方案（例如，这可能是在面板上覆盖 getGaphics 可能是合适的极少数情况之一），但无济于事 . 也许通常的嫌疑人（camickr，气垫船等）找到一个更优雅和简洁的解决方案 .

  在此之前，这里的代码是MCVE：

  import java.awt.AlphaComposite;
  import java.awt.BorderLayout;
  import java.awt.Color;
  import java.awt.Component;
  import java.awt.Graphics;
  import java.awt.Graphics2D;
  import java.awt.image.BufferedImage;
  
  import javax.swing.JButton;
  import javax.swing.JComponent;
  import javax.swing.JFrame;
  import javax.swing.JLabel;
  import javax.swing.JPanel;
  import javax.swing.JSlider;
  import javax.swing.JTree;
  import javax.swing.RepaintManager;
  import javax.swing.SwingUtilities;
  
  public class TransparencyPanelTest
  {
      public static void main(String[] args)
      {
          SwingUtilities.invokeLater(() -> createAndShowGui());
      }
  
      private static void createAndShowGui()
      {
          JFrame f = new JFrame();
          f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          f.getContentPane().setLayout(new BorderLayout());
  
          OpacityPanel opacityPanel = new OpacityPanel();
  
          opacityPanel.setLayout(new BorderLayout());
          opacityPanel.add(new JLabel("Label"), BorderLayout.NORTH);
          opacityPanel.add(new JTree(), BorderLayout.CENTER);
          opacityPanel.add(new JButton("Button"), BorderLayout.SOUTH);
  
          f.getContentPane().add(opacityPanel, BorderLayout.CENTER);
  
          JSlider slider = new JSlider(0, 100, 50);
          slider.addChangeListener(e -> 
              opacityPanel.setOpacity(slider.getValue() / 100.0f));
          f.getContentPane().add(slider, BorderLayout.SOUTH);
  
          f.setSize(500,500);
          f.setLocationRelativeTo(null);
          f.setVisible(true);
      }
  
  }
  
  class OpacityPanel extends JPanel
  {
      static
      {
          RepaintManager.setCurrentManager(new RepaintManager()
          {
              @Override
              public void addDirtyRegion(
                  JComponent c, int x, int y, int w, int h)
              {
                  Component cc = c;
                  while (cc != null)
                  {
                      if (cc instanceof OpacityPanel)
                      {
                          OpacityPanel p = (OpacityPanel)cc;
                          super.addDirtyRegion(
                              p, 0, 0, p.getWidth(), p.getHeight());
                      }
                      cc = cc.getParent();
                  }
                  super.addDirtyRegion(c, x, y, w, h);
              }
          });
      }
      private float opacity = 0.5f;
      private BufferedImage image;
  
      public OpacityPanel()
      {
          setOpaque(false);
      }
  
      public void setOpacity(float opacity)
      {
          this.opacity = Math.max(0.0f, Math.min(1.0f, opacity));
          repaint();
      }
  
      private void updateImage()
      {
          int w = Math.min(1, getWidth());
          int h = Math.min(1, getHeight());
          if (image == null || image.getWidth() != w || image.getHeight() != h)
          {
              image = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
          }
          Graphics2D g = image.createGraphics();
          g.setColor(new Color(0,0,0,0));
          g.setComposite(AlphaComposite.SrcOver);
          g.fillRect(0, 0, w, h);
          g.dispose();
      }
  
      @Override
      protected void paintComponent(Graphics gr)
      {
          updateImage();
          Graphics2D imageGraphics = image.createGraphics();
          super.paintComponent(imageGraphics);
          imageGraphics.dispose();
  
          Graphics2D g = (Graphics2D) gr;
          g.setComposite(AlphaComposite.getInstance(
              AlphaComposite.SRC_OVER, opacity));
          g.drawImage(image, 0, 0, null);
      }
  
  }
  

  回复于 2024-04-20T02:15:51+08:00