我正在开发一个Swing应用程序，我对GridBagLayout有一个很大的问题。该程序在 BorderLayout 中的滚动窗格中添加动态按钮，但是当我调整窗口大小时，第一个按钮比其他按钮大，为什么？

    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 450, 300);
    contentPane = new JPanel();
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    setContentPane(contentPane);
    contentPane.setLayout(new BorderLayout(0, 0));
    
    JScrollPane scrollPane = new JScrollPane();
    scrollPane.setPreferredSize(new Dimension(140, 2));
    contentPane.add(scrollPane, BorderLayout.WEST);
    
    JPanel panel = new JPanel();
    scrollPane.setViewportView(panel);
    GridBagLayout gbl_panel = new GridBagLayout();
    gbl_panel.columnWidths = new int[]{0};
    gbl_panel.rowHeights = new int[]{0};
    gbl_panel.columnWeights = new double[]{Double.MIN_VALUE};
    gbl_panel.rowWeights = new double[]{Double.MIN_VALUE};
    panel.setLayout(gbl_panel);
    
    
    int counter=0;
    for(String nomeNazione:nazioni)
    {
        
        btn = new JButton(nomeNazione);
        GridBagConstraints gbc_btn = new GridBagConstraints();
        gbc_btn.insets = new Insets(0, 0, 0, 0);
        gbc_btn.gridx = 0;
        gbc_btn.gridy = counter;
        gbc_btn.fill = GridBagConstraints.BOTH;
        gbc_btn.weighty=1;
        
        
        panel.add(btn, gbc_btn);
        counter++;
    }