1

就像标题所说的那样——我有一个 JPanel，如果不活动，我希望它的不透明度为 90%，如果鼠标悬停，则为完全不透明度。

我已经让单独的组件工作了 - 鼠标悬停和移出是可以的，我可以通过覆盖paintComponent方法来更改不透明度，但我想我在连接MouseAdapter 和paintComponent.

似乎有一种非常简单的方法可以做到这一点 - 任何提示？

（顺便说一句，抱歉把代码留在家里了，所以暂时没有例子：（除非它不能很快解决，否则我明天会抛出一些代码。）

4

3 回答 3

4

如果您要覆盖该paintComponent方法，您应该能够向JPanel扩展添加一个不透明度变量。MouseAdapter在(using mutators)中修改它。然后在被覆盖的方法中引用这个变量paintComponent来决定如何绘制。

于 2011-07-29T00:20:21.447 回答
3

如果您已经覆盖了paintComponent 方法，我建议您将MouseAdapter 设为Panel 的匿名内部类，并让它操作一个私有布尔标志。

public class FadingPanel extends JPanel
{
    private boolean active;

    public FadingPanel()
    {
        createMouseAdapter();
    }

    private void createMouseAdapter()
    {
        this.addMouseListener(new MouseAdapter()
        {
            // your mouseadapter code here toggling the active flag
        } 
    }

    @Override
    public boolean paintComponent(Graphics g)
    {
         if(active)
         {
              super.paintComponent(g);
         }
         else
         {
              // your semitransparent painting code here
         }
    }
}
于 2011-07-29T00:19:58.640 回答
3

射击，我没有 Haase 和 Guy 的书，我不记得他们建议为半透明组件编码的方式，但我猜想覆盖paint或paintComponent的工作，除了覆盖paint会显示对孩子的影响组件从一开始。例如：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class OpaqueJPanels {

   private static void createAndShowUI() {
      JPanel mainPanel = new JPanel(new GridLayout(1, 0));
      mainPanel.add(new OpaqueJPanel(false, "Override paintComponent"));
      mainPanel.add(new OpaqueJPanel(true, "Override paint"));

      JFrame frame = new JFrame("Opaque JPanels");
      frame.getContentPane().add(mainPanel);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      java.awt.EventQueue.invokeLater(new Runnable() {
         public void run() {
            createAndShowUI();
         }
      });
   }
}

class OpaqueJPanel extends JPanel {
   private static final int OJP_WIDTH = 250;
   private static final int OJP_HEIGHT = OJP_WIDTH;
   private static final Composite TRANSLUSCENT_COMPOSITE = AlphaComposite
            .getInstance(AlphaComposite.SRC_OVER, 0.4f);
   private static final Composite NON_TRANSLUSCENT_COMPOSITE = AlphaComposite
            .getInstance(AlphaComposite.SRC_OVER, 1.0f);
   private boolean overridePaint;
   private boolean transluscent = true;

   public OpaqueJPanel(boolean overridePaint, String title) {
      add(new JButton("Button"));
      setBorder(BorderFactory.createTitledBorder(title));
      addMouseListener(new MouseAdapter() {
         @Override
         public void mouseEntered(MouseEvent e) {
            transluscent = false;
            getParent().repaint();
         }

         @Override
         public void mouseExited(MouseEvent e) {
            if (!OpaqueJPanel.this.contains(e.getPoint())) {
               transluscent = true;
               getParent().repaint();
            }
         }
      });
   }

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

   @Override
   public void paint(Graphics g) {
      if (!overridePaint) {
         super.paint(g);
         return;
      }
      Graphics2D g2 = (Graphics2D) g;
      Composite composite = transluscent ? TRANSLUSCENT_COMPOSITE
               : NON_TRANSLUSCENT_COMPOSITE;
      g2.setComposite(composite);
      super.paint(g);
   }

   @Override
   protected void paintComponent(Graphics g) {
      if (overridePaint) {
         super.paintComponent(g);
         return;
      }
      Graphics2D g2 = (Graphics2D) g;
      Composite composite = transluscent ? TRANSLUSCENT_COMPOSITE
               : NON_TRANSLUSCENT_COMPOSITE;
      g2.setComposite(composite);
      super.paintComponent(g);
   }
}

我还发现如果我重新绘制 JPanel 的父组件而不是 JPanel 本身会更好。

于 2011-07-29T02:00:47.877 回答