如何在 JLayeredPane 上设置背景颜色？

Question

我很好奇为什么在 JLayeredPane 上调用 setBackground(Color) 似乎并没有真正设置背景颜色。我猜这与 JLayeredPane 出于某种原因必须具有透明背景有关吗？无论如何，这里有一些显示问题的代码。这是在 Mac 上，所以我相信它使用的是 OSX LAF。这产生的结果由this image 显示。

import java.awt.Color;
import java.awt.Dimension;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLayeredPane;
import javax.swing.JPanel;

public class Main {
    public static void main(String[] args) {

        // This should be done with Swing Utilities, but I wanted to keep this
        // simple...
        JFrame foo = new JFrame();
        foo.setSize(new Dimension(500, 500));

        JLayeredPane bar = new JLayeredPane();
        bar.setPreferredSize(new Dimension(200, 200));
        bar.setBackground(Color.red);

        // If you comment out the following line, you don't see any indication
        // the JLayeredPane is actually being drawn to screen
        bar.setBorder(BorderFactory.createLineBorder(Color.green));


        JPanel content = new JPanel();
        content.add(bar);

        foo.setContentPane(content);
        foo.setVisible(true);
    }
}

Answer 1

您可以尝试使分层窗格不透明：

bar.setOpaque(true);