产生滚动条时JPanel的大小发生变化

使用java swing编写一个小工具时遇到一个问题

界面如下:

 

红框中的内容是一个JPanel,代码如下

panel_9 = new JPanel();
		panel_9.setLayout(new GridLayout(1, 3));
		
		panel_9.setBorder(new LineBorder(Color.GREEN));
		GridBagConstraints gbc_panel_9 = new GridBagConstraints();
		gbc_panel_9.anchor = GridBagConstraints.WEST;
		gbc_panel_9.insets = new Insets(0, 0, 5, 5);
		gbc_panel_9.fill = GridBagConstraints.VERTICAL;
		gbc_panel_9.gridx = 2;
		gbc_panel_9.gridy = 1;
		panel_8.add(panel_9, gbc_panel_9);
		

但是当下面的JScrollPane 有滚动条时panel就自动缩小了,如下图

 

解决方法:

把panel的 gbc_scrollPane_1.fill  由GridBagConstraints.VERTICAL改为GridBagConstraints.BOTH