JSwing 拆分窗格不会显示

Question

我正在用Java创建一个简单的信使（仅用于学习目的），我正在尝试有一个朋友选项卡，左侧是朋友列表，右侧是您单击的朋友的消息，但是每当我尝试在选项卡中添加JSplitPane时， 但它不显示。我已经完成了完全相同的代码（除了我只做了JSplitPane的东西及其组件，没有做其他选项卡和菜单等。

我所有的代码

package Client;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Box;
import javax.swing.DefaultListModel;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JPanel;
import javax.swing.JRadioButtonMenuItem;
import javax.swing.JScrollPane;
import javax.swing.JSplitPane;
import javax.swing.JTabbedPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.ListSelectionModel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class ClientMain extends JFrame {
int WIDTH = 640;
int HEIGHT = 480;
JTabbedPane tabbedPane;
JMenuBar topMenuBar;
JMenu userMenu, helpMenu, settingsMenu;
JRadioButtonMenuItem menuItem;
JPanel mainPanel, friendsPanel, groupsPanel, testPanel;
JLabel title;
JScrollPane consoleScrollPane, friendChatScrollPane, friendListScrollPane;
JSplitPane friendsSplitPane;
JTextArea friendChatArea, testArea;
JTextField friendChatField, testField;
JList friendList;
Box box;
DefaultListModel friends;
public ClientMain() {
    super("Messenger Client");
    //Networking();

    /** MAIN PANEL **/

        title = new JLabel("Client!");
        title.setFont(new Font("Impact", Font.PLAIN, 32));
        mainPanel = new JPanel();
        mainPanel.setLayout(null);
        mainPanel.add(title);
    /** TEST PANEL **/

        groupsPanel = new JPanel();
        groupsPanel.setLayout(null);

    /** FRIENDS PANEL **/

        friendsPanel = new JPanel();
        friendsPanel.setLayout(null);
        friends = new DefaultListModel();
        //method here that retrieves users' friends from the server and adds them to the friends DefaultListModel
        friends.addElement("Person1");
        friends.addElement("Person2");
        friendList = new JList(friends);
        friendList.setSelectionMode(ListSelectionModel.SINGLE_INTERVAL_SELECTION);
        friendList.setLayoutOrientation(JList.VERTICAL_WRAP);
        friendList.setVisibleRowCount(3);
        friendList.setSize(50, 50);
        friendChatArea = new JTextArea();
        friendChatArea.setSize(50, 50);
        friendChatArea.setFont(new Font("", Font.PLAIN, 13 + 1/2));
        friendChatArea.append("TEST");
        Dimension minimumSize = new Dimension(100, 50);
        friendListScrollPane = new JScrollPane(friendList);
        friendListScrollPane.setMinimumSize(minimumSize);
        friendChatScrollPane = new JScrollPane(friendChatArea);
        friendChatScrollPane.setMinimumSize(minimumSize);
        friendsSplitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, friendListScrollPane, friendChatScrollPane);
        friendsSplitPane.setOneTouchExpandable(false);
        friendsSplitPane.setDividerLocation(50);
        friendsPanel.add(friendsSplitPane);
    /** TEST PANEL **/

        testPanel = new JPanel();
        testPanel.setLayout(null);
        testArea = new JTextArea();
        testArea.setFont(new Font("", Font.PLAIN, 13 + 1/2));
        testArea.setBounds(0, 0, WIDTH, HEIGHT - 100);
        testArea.setEditable(false);
        testArea.setLineWrap(true);
        testField = new JTextField(20);
        testField.setBounds(0, 380, 640, 25);
        //testField.setLocation(0, HEIGHT - 50);
        testField.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                ClientNet net = new ClientNet();
                String input = null;
                input = testField.getText();
                testArea.append(input);
                testField.setText("");
                if(input.equalsIgnoreCase("/sendmessage")) {
                    testArea.append("n Input who you would like to send the message to:");
                    input = null;
                    if(input.equalsIgnoreCase("Hello")) {
                        net.userEntry = input;
                    }
                }
            }
        });
        testPanel.add(testArea);
        testPanel.add(testField);

    /** SET UP **/

        tabbedPane = new JTabbedPane();
        tabbedPane.add(mainPanel, "Main");
        tabbedPane.add(friendsPanel, "Friends");
        tabbedPane.add(groupsPanel, "Groups");
        tabbedPane.add(testPanel, "Test");
        topMenuBar = new JMenuBar();
        userMenu = new JMenu("User");
        settingsMenu = new JMenu("Settings");
        helpMenu = new JMenu("Help");
        menuItem = new JRadioButtonMenuItem("Something here");
        userMenu.add(menuItem);
        topMenuBar.add(userMenu, "User");
        topMenuBar.add(settingsMenu, "Settings");
        topMenuBar.add(helpMenu, "Help");
        add(topMenuBar);
        add(tabbedPane);
}
public static void main(String[] args) {
    try {
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    } catch(UnsupportedLookAndFeelException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (InstantiationException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    }
    ClientMain frame = new ClientMain();
    Insets insets = frame.getInsets();
    frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
    frame.setSize(frame.WIDTH, frame.HEIGHT);
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
    frame.setResizable(false);
    frame.setJMenuBar(frame.topMenuBar);
}
public void Networking() {
    ClientNet net;
    try {
        net = new ClientNet();
        net.start();
    } catch(Exception e) {
        e.printStackTrace();
    }
}
public void createMenuBar() {
    topMenuBar = new JMenuBar();
    userMenu = new JMenu("User");
    settingsMenu = new JMenu("Settings");
    helpMenu = new JMenu("Help");
    menuItem = new JRadioButtonMenuItem("MenuItem");
    menuItem.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
        }
    });
    topMenuBar.add(userMenu, "User");
    topMenuBar.add(settingsMenu, "Settings");
    topMenuBar.add(helpMenu, "Help");
}
public void createSplitPane() {
    friendListScrollPane = new JScrollPane();
    friendListScrollPane.add(new JLabel("Hello"));
    friendChatArea = new JTextArea();
    friendChatArea.setBounds(0, 150, HEIGHT, HEIGHT);
    friendChatArea.setFont(new Font("", Font.PLAIN, 13 + 1/2));
    Dimension minimumSize = new Dimension(WIDTH/2 , HEIGHT);
    friendListScrollPane.setMinimumSize(minimumSize);
    //friendsSplitPane.setLeftComponent()
    friendsSplitPane.add(friendChatArea);
    friendsSplitPane.setRightComponent(friendChatScrollPane);
}

}

特定的JSplitPane代码（上面代码的一部分）

friendsPanel = new JPanel();
        friendsPanel.setLayout(null);
        friends = new DefaultListModel();
        //method here that retrieves users' friends from the server and adds them to the friends DefaultListModel
        friends.addElement("Person1");
        friends.addElement("Person2");
        friendList = new JList(friends);
        friendList.setSelectionMode(ListSelectionModel.SINGLE_INTERVAL_SELECTION);
        friendList.setLayoutOrientation(JList.VERTICAL_WRAP);
        friendList.setVisibleRowCount(3);
        friendList.setSize(50, 50);
        friendChatArea = new JTextArea();
        friendChatArea.setSize(50, 50);
        friendChatArea.setFont(new Font("", Font.PLAIN, 13 + 1/2));
        friendChatArea.append("TEST");
        Dimension minimumSize = new Dimension(100, 50);
        friendListScrollPane = new JScrollPane(friendList);
        friendListScrollPane.setMinimumSize(minimumSize);
        friendChatScrollPane = new JScrollPane(friendChatArea);
        friendChatScrollPane.setMinimumSize(minimumSize);
        friendsSplitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, friendListScrollPane, friendChatScrollPane);
        friendsSplitPane.setOneTouchExpandable(false);
        friendsSplitPane.setDividerLocation(50);
        friendsPanel.add(friendsSplitPane);

Answer 1

friendsPanel.setLayout(null);

您的friendsPanel具有空布局，并且您要将拆分窗格添加为：

friendsPanel.add(friendsSplitPane);

要将component添加到具有 null 布局的容器（ friendsPanel ），必须指定使用 component.setBounds() 方法添加的组件的边界。但说真的，为什么还要使用null布局？不要使用它。堆栈溢出的摇摆家族已经从一页到另一页地建议了。尝试使用 Swing 开发人员为我们创建的布局管理器之一，日复一日地浪费时间，只是为了节省我们自己的时间。

开始学习：课程：在容器中布置组件。让我们珍惜他们为节省我们的时间所作的努力，我们花费这些努力只是为了找到答案：uhh! where is my component!?!