如何使 JLayeredPane() 和 JPanel() 透明？它总是显示超级窗口的背景

Question

我怎样才能完全使这个灰色面板透明，以便我只能看到按钮“测试”，而看不到灰色框（JPanel或JLayeredPane）

屏幕截图：< img src="https://i.sstatic.net/Go57H.png" alt="在此处输入图像描述">

public class win extends JWindow 
{
    ...

    public win() 
    {
        super(new JFrame());
        layers = new JLayeredPane();
        button = new JButton("close");

        this.setLayout (new BorderLayout ());
        ..

        button.setBackground(Color.RED);
        button.setSize(200,200);
        button.setLocation(0,20);
        this.add("North", button);

        JPanel p = new JPanel();
        p.setOpaque(false);
        p.setSize(300, 200);
        p.setLocation(0, 0);
        p.add(new JButton("Test"));

        layers.add(p, new Integer(1));
        layers.setSize(400,300);
        layers.setLocation(400,50);
        layers.setOpaque(false);
        this.add("North", layers);

        canvas.setSize(screenSize.width,screenSize.height);
        this.add("North",canvas);
        //com.sun.awt.AWTUtilities.setWindowOpacity(this, 0.5f); // gives error in my Java version

    }
}

后续： 按照建议安装，但还没有成功。

ERROR not solved: Exception in thread "main" java.lang.UnsupportedOperationException: The TRANSLUCENT translucency kind is not supported.

Installed:
  compiz-gnome.i686 0:0.9.4-2.fc15                                                      

Dependency Installed:
  compiz-gtk.i686 0:0.9.4-2.fc15           compiz-plugins-main.i686 0:0.9.4-1.fc15     
  libcompizconfig.i686 0:0.9.4-1.fc15      protobuf.i686 0:2.3.0-7.fc15                

Complete!
You have mail in /var/spool/mail/root
[root@example ~]# xdpyinfo | grep -i render
    RENDER
You have mail in /var/spool/mail/root
[root@example ~]# xdpyinfo | grep -i comp
    Composite
    XVideo-MotionCompensation
[root@example ~]# 

Answer 1

请参阅本文或本文。请注意，并非所有环境都支持本文中描述的所有功能（半透明度、每像素透明度等）。

编辑：在我的系统（Ubuntu 10.04.2 LTS，Sun java 1.6.0_26）上，以下代码：

  System.out.println("TRANSLUCENT supported:          " + AWTUtilities.isTranslucencySupported(AWTUtilities.Translucency.TRANSLUCENT));
  System.out.println("PERPIXEL_TRANSPARENT supported: " + AWTUtilities.isTranslucencySupported(AWTUtilities.Translucency.PERPIXEL_TRANSPARENT));
  System.out.println("PERPIXEL_TRANSLUCENT supported: " + AWTUtilities.isTranslucencySupported(AWTUtilities.Translucency.PERPIXEL_TRANSLUCENT));

给出：

TRANSLUCENT supported:          false
PERPIXEL_TRANSPARENT supported: true
PERPIXEL_TRANSLUCENT supported: true

编辑2：灵感来自此讨论，我刚刚安装并配置了 compiz，现在是“恒定不透明度”上面链接的第二篇文章中 Web Start 应用程序的“level”滑块突然可以移动到小于 100% 的值，并且演示框架实际上是半透明的。此外，上面显示的代码片段现在为所有三种半透明/透明度打印 true。并且 AWTUtilities.setWindowOpacity(..) 不再抛出任何异常，而是生成一个透明窗口。