JPanel 和自定义 Class 扩展 JPanel 显示不正确

Question

我在从我的主 GUI class 中提取大量代码并将它们放入较小的可管理 classes 时遇到了一个小错误。

所以我用一个非常简单的 GUI 做了另一个测试，发现同样的错误发生在那里，尽管唯一的区别是代码在不同的位置。

第一个 JPanel 正确显示并填充整个布局。扩展 JPanel 的第二个 TestPanel 显示不正确，只占布局的一小部分。

两个 classes 具有完全相同的 GridBagLayout 并且两个 JScrollPanes 具有相同的 GridBagConstraints。

这是我的主要 class，其中包含一个包含两个 JPanel 的 JTabbedPane，每个 JPanel 的视口中都有一个 JTextArea。

import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JTabbedPane;
import javax.swing.SwingConstants;
import java.awt.BorderLayout;
import javax.swing.JPanel;
import java.awt.GridBagLayout;
import javax.swing.JScrollPane;
import java.awt.GridBagConstraints;
import javax.swing.JTextArea;

public class TestMainGUI
{
    private JFrame frame;
    private JTabbedPane tabbedPane;
    private JPanel workingDefaultPanel;
    private JScrollPane workingDefaultScrollPane;
    private JTextArea workingDefaultJTextArea;
    private TestJPanel notWorkingExtendingJPanel;

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                try
                {
                    TestMainGUI window = new TestMainGUI();
                    window.frame.setVisible(true);
                }
                catch (Exception e)
                {
                    e.printStackTrace();
                }
            }
        });
    }

    public TestMainGUI()
    {
        initialize();
    }

    private void initialize()
    {
        frame = new JFrame();
        frame.setBounds(100, 100, 450, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //******************************************************************//
        tabbedPane = new JTabbedPane(SwingConstants.TOP);
        frame.getContentPane().add(tabbedPane, BorderLayout.CENTER);
        //******************************************************************//
        workingDefaultPanel = new JPanel();
        tabbedPane.addTab("Working Panel", null, workingDefaultPanel, null);
        GridBagLayout gbl_WorkingDefaultPanel = new GridBagLayout();
        gbl_WorkingDefaultPanel.columnWidths = new int[]{0, 0};
        gbl_WorkingDefaultPanel.rowHeights = new int[]{0, 0};
        gbl_WorkingDefaultPanel.columnWeights = new double[]{1.0, Double.MIN_VALUE};
        gbl_WorkingDefaultPanel.rowWeights = new double[]{1.0, Double.MIN_VALUE};
        workingDefaultPanel.setLayout(gbl_WorkingDefaultPanel);
        //******************************************************************//
        workingDefaultScrollPane = new JScrollPane();
        GridBagConstraints gbc_scrollPane = new GridBagConstraints();
        gbc_scrollPane.fill = GridBagConstraints.BOTH;
        gbc_scrollPane.gridx = 0;
        gbc_scrollPane.gridy = 0;
        workingDefaultPanel.add(workingDefaultScrollPane, gbc_scrollPane);
        //******************************************************************//
        workingDefaultJTextArea = new JTextArea();
        workingDefaultScrollPane.setViewportView(workingDefaultJTextArea);
        //******************************************************************//
        notWorkingExtendingJPanel = new TestJPanel();
        tabbedPane.addTab("Non Working Panel", null, notWorkingExtendingJPanel, null);
        GridBagLayout gbl_panel_1 = new GridBagLayout();
        gbl_panel_1.columnWidths = new int[]{0, 0};
        gbl_panel_1.rowHeights = new int[]{0, 0};
        gbl_panel_1.columnWeights = new double[]{1.0, Double.MIN_VALUE};
        gbl_panel_1.rowWeights = new double[]{1.0, Double.MIN_VALUE};
        notWorkingExtendingJPanel.setLayout(gbl_panel_1);
    }
}

这是我的 TestJPanel

import java.awt.GridBagConstraints;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class TestJPanel extends JPanel
{
    private static final long serialVersionUID = 5041143050449865233L;
    private JScrollPane notWorkingJScrollPane;
    private JTextArea notWorkingJTextArea;

    public TestJPanel()
    {
        super();
        notWorkingJScrollPane = new JScrollPane();
        GridBagConstraints gbc_notWorkingScrollPane = new GridBagConstraints();
        gbc_notWorkingScrollPane.fill = GridBagConstraints.BOTH;
        gbc_notWorkingScrollPane.gridx = 0;
        gbc_notWorkingScrollPane.gridy = 0;
        this.add(notWorkingJScrollPane, gbc_notWorkingScrollPane);
        //******************************************************************//
        notWorkingJTextArea = new JTextArea();
        notWorkingJScrollPane.setViewportView(notWorkingJTextArea);
    }

    protected JScrollPane getNotWorkingJScrollPane()
    {
        return notWorkingJScrollPane;
    }

    protected JTextArea getNotWorkingJTextArea()
    {
        return notWorkingJTextArea;
    }
}

Answer 1

notWorkingExtendingJPanel.setLayout(gbl_panel_1);

我猜问题是在将组件添加到面板后无法设置布局。

上面的语句和所有网格包布局逻辑应该在您的 TestJPanel class 中，您可以在其中创建组件并将其添加到面板。

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