无法更改布局边框颜色

Question

我正在做一个简单的 Swing 布局（请参阅 image），但由于某种原因，无论我尝试什么，我都无法更改分隔 UI 三个部分的“边框”的颜色。我错过了什么吗？

布局是使用 GroupLayout 完成的。

编辑：

绿色部分是 GroupLayout 中包含的每个单独的 JPanel。

我已经在任何有意义的对象上尝试了背景色和前景色。我尝试将 EmptyBorder 应用于每个 jpanels，但仍然没有运气。我认为这可能与布局有关，但我什至不确定。

这是相关的布局代码。请注意，这都是由 Netbeans 自动生成的：

    javax.swing.GroupLayout pnlTopLayout = new javax.swing.GroupLayout(pnlTop);
        pnlTop.setLayout(pnlTopLayout);
        pnlTopLayout.setHorizontalGroup(
            pnlTopLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 532, Short.MAX_VALUE)
        );
        pnlTopLayout.setVerticalGroup(
            pnlTopLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 59, Short.MAX_VALUE)
        );

javax.swing.GroupLayout pnlSideLayout = new javax.swing.GroupLayout(pnlSide);
        pnlSide.setLayout(pnlSideLayout);
        pnlSideLayout.setHorizontalGroup(
            pnlSideLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 200, Short.MAX_VALUE)
        );
        pnlSideLayout.setVerticalGroup(
            pnlSideLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 214, Short.MAX_VALUE)
        );

javax.swing.GroupLayout pnlMainLayout = new javax.swing.GroupLayout(pnlMain);
        pnlMain.setLayout(pnlMainLayout);
        pnlMainLayout.setHorizontalGroup(
            pnlMainLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 326, Short.MAX_VALUE)
        );
        pnlMainLayout.setVerticalGroup(
            pnlMainLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 214, Short.MAX_VALUE)
        );

javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addComponent(pnlSide, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(pnlMain, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
            .addComponent(pnlTop, javax.swing.GroupLayout.DEFAULT_SIZE, 532, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addComponent(pnlTop, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(pnlMain, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(pnlSide, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)))
        );

Answer 1

您应该设置容器内容窗格的背景颜色，或者覆盖它的JComponent（例如JPanel）。

---

public final class Demo {
    private static BufferedImage bi;
    
    public static void main(String[] args){
        try {
            loadImage();
            
            SwingUtilities.invokeLater(new Runnable(){
                @Override
                public void run() {
                    createAndShowGUI();             
                }
            });
        } catch (IOException e) {
            // handle exception
        }
    }
    
    private static void loadImage() throws IOException{
        bi = ImageIO.read(Demo.class.getResource("../resources/whitefro1.jpg"));
    }
    
    private static void createAndShowGUI(){
        final JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        final JPanel panel = new JPanel();
        panel.setBackground(Color.BLUE.darker()); // here
        
        final JLabel labelOne = new JLabel();
        labelOne.setIcon(new ImageIcon(bi));
        final JLabel labelTwo = new JLabel();
        labelTwo.setIcon(new ImageIcon(bi));
        
        panel.add(labelOne);
        panel.add(labelTwo);
        frame.add(panel);       
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

---

如您所见，中间的区域被染成深蓝色。