如何设置JPanel的透明背景？

问题描述

JPanel 的背景设置为透明？

我的框架是有两个 JPanel s：

• 图片面板和


• 功能面板。
  $ b
功能面板与图片面板重叠。
图像面板用作背景，它从远程URL加载图像。



在功能面板上我想绘制形状。由于功能面板背景色，现在图像面板无法显示。





我需要使功能面板背景透明，同时仍然绘制其形状，并且我希望 Image Panel 可见（因为它正在做图像的平铺和缓存功能）。





我使用两个 JPanel 的，因为我需要分离图片和形状图。





有没有一种方法使重叠的Jpanel具有透明背景？


解决方案

或者，考虑，在文章。您可以在玻璃窗格的 paintComponent（）方法中绘制您的特征内容。





附录：使用，我加入了一个图像：



  / *设置内容窗格，其中主GUI位于此处。 * / 
 frame.add（changeButton，BorderLayout.SOUTH）; 
 frame.add（new JLabel（new ImageIcon（img.jpg）），BorderLayout.CENTER）; 
  

并修改了玻璃窗格的 paintComponent（）方法：
$ b

  protected void paintComponent（Graphics g）{
 if（point！= null）{
 Graphics2D g2d =（Graphics2D）g; 
 g2d.setRenderingHint（
 RenderingHints.KEY_ANTIALIASING，
 RenderingHints.VALUE_ANTIALIAS_ON）; 
 g2d.setComposite（AlphaComposite.getInstance（
 AlphaComposite.SRC_OVER，0.3f））; 
 g2d.setColor（Color.yellow）; 
 g2d.fillOval（point.x，point.y，120，60）; 
} 
} 
  




Can JPanels background be set to transparent?

My frame is has two JPanels:

• Image Panel and
• Feature Panel.

Feature Panel is overlapping Image Panel.The Image Panel is working as a background and it loads image from a remote URL.

On Feature Panel I want to draw shapes. Now Image Panel cannot be seen due to Feature Panel's background color.

I need to make Feature Panel background transparent while still drawing its shapes and I want Image Panel to be visible (since it is doing tiling and cache function of images).

I'm using two JPanel's, because I need to seperate the image and shape drawing .

Is there a way the overlapping Jpanel have a transparent background?

解决方案

Alternatively, consider The Glass Pane, discussed in the article How to Use Root Panes. You could draw your "Feature" content in the glass pane's paintComponent() method.

Addendum: Working with the GlassPaneDemo, I added an image:

/* Set up the content pane, where the "main GUI" lives. */
frame.add(changeButton, BorderLayout.SOUTH);
frame.add(new JLabel(new ImageIcon("img.jpg")), BorderLayout.CENTER);

and altered the glass pane's paintComponent() method:

protected void paintComponent(Graphics g) {
    if (point != null) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setRenderingHint(
            RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setComposite(AlphaComposite.getInstance(
            AlphaComposite.SRC_OVER, 0.3f));
        g2d.setColor(Color.yellow);
        g2d.fillOval(point.x, point.y, 120, 60);
    }
}

image http://i41.tinypic.com/2j0mlv9.png

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