滚动条没有出现在三个滚动窗格之一中

Question

我有一个包含三个scrollpane的简单程序。我把它设置为滚动条总是可见的。由于某种原因，滚动条只在三个窗格中的两个可见，尽管这三个窗格的代码是相同的。它们之间唯一的区别是第三个(有问题的窗格)位于边界布局的南部区域。

代码:

package SwingAssign2;
import java.awt.Dimension;
import java.awt.EventQueue;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import java.awt.BorderLayout;
import javax.swing.JComboBox;
import javax.swing.JTextField;
import java.awt.FlowLayout;
import javax.swing.SwingConstants;
import java.awt.GridLayout;
public class SwingAssign2 {
    private JFrame frame;
    private JTextField textField;
    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    SwingAssign2 window = new SwingAssign2();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }
    /**
     * Create the application.
     */
    public SwingAssign2() {
        initialize();
    }
    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.setSize(600, 500);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panelTop = new JPanel();
        FlowLayout fl_panelTop = (FlowLayout) panelTop.getLayout();
        fl_panelTop.setAlignment(FlowLayout.LEFT);
        frame.getContentPane().add(panelTop, BorderLayout.NORTH);
        //panel.setLayout(new FlowLayout(FlowLayout.LEFT, 5, 5));
        JComboBox comboBox = new JComboBox();
        panelTop.add(comboBox);
        comboBox.setPreferredSize(new Dimension(100, 20));
        textField = new JTextField();
        panelTop.add(textField);
        textField.setColumns(20);
        JPanel panelBottom = new JPanel();
        frame.getContentPane().add(panelBottom, BorderLayout.SOUTH);
        panelBottom.setLayout(new BorderLayout(0, 0));
        JLabel status = new JLabel("Status");
        status.setHorizontalAlignment(SwingConstants.CENTER);
        panelBottom.add(status, BorderLayout.SOUTH);
        status.setBorder(BorderFactory.createLoweredBevelBorder());
        JTextPane bText = new JTextPane();
        JScrollPane jScrollPane3 = new JScrollPane();
        jScrollPane3.setHorizontalScrollBarPolicy(
                JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
        jScrollPane3.setVerticalScrollBarPolicy(
                JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
        panelBottom.add(bText, BorderLayout.NORTH);
        bText.setPreferredSize(new Dimension(200, 200));
        //bText.setBorder(BorderFactory.createLoweredBevelBorder());
        JPanel panelCenter = new JPanel();
        frame.getContentPane().add(panelCenter, BorderLayout.CENTER);
        panelCenter.setLayout(new GridLayout(0, 2, 0, 0));
        JTextPane textPane_0 = new JTextPane();
        JScrollPane jScrollPane1 = new JScrollPane();
        jScrollPane1.setHorizontalScrollBarPolicy(
                JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
        jScrollPane1.setVerticalScrollBarPolicy(
                JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
        panelCenter.add(jScrollPane1);
        JTextPane textPane_1 = new JTextPane();
        JScrollPane jScrollPane2 = new JScrollPane(textPane_1);
        jScrollPane2.setHorizontalScrollBarPolicy(
                JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
        jScrollPane2.setVerticalScrollBarPolicy(
                JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
        panelCenter.add(jScrollPane2);
    }
}

Answer 1

因为一个愚蠢的错误。

panelBottom.add(bText, BorderLayout.NORTH);

应该

panelBottom.add(jScrollPane3, BorderLayout.NORTH);