Question

所以，让我们从一些背景开始，这是第一年的拼贴项目。 GUI构建为一个类，接口处理程序调用所有JPanel并将它们放在正确的位置。这是为了结构，因此易于维护。

问题是拿着菜单的面板在添加之后不会显示它的组件。我会包含一些图片，以便更容易理解。

相关面板名为MenuPanel。

所以这里是登录按钮，目前只清除内容面板，然后添加菜单面板。

这里是菜单面板空

代码接口处理程序你可以看到我已经在菜单方法中使用.repaint（）方法搞乱了。公共类InterfaceHandler {

private static InterfaceHandler singleton;

/**
 * Checks if there is already a instance running of InterfaceHandler if so
 * return the instance if not create a instance.
 *
 * @return Instance
 */
public static InterfaceHandler instance() {
    if (singleton == null) {
        singleton = new InterfaceHandler();
    }

    return singleton;
}

private ContentPanel contentPanel;
private LoginPanel loginPanel;
private MainFrame mainFrame;
private MainPanel mainPanel;
private MenuPanel menuPanel;

/**
 * Initializes default Interface
 */
public InterfaceHandler() {
    initComponents();

}

/**
 * Initializes GUI Components that will be needed now or in the future.
 */
public void initComponents() {
    mainFrame = new MainFrame();
    mainPanel = new MainPanel();
    contentPanel = new ContentPanel();
    loginPanel = new LoginPanel();
    menuPanel = new MenuPanel();

    contentPanel.setBounds(100, 100, 860, 700);
    menuPanel.setBounds(10, 10, 80, 400);
    loginPanel.setBounds(280, 250, 300, 200);

    mainFrame.add(mainPanel);
    mainPanel.add(contentPanel);

    mainFrame.setVisible(true);
    contentPanel.add(loginPanel);
}

/**
 * Clears the ContentPanel of all components
 */
public void clear() {
    System.out.println("Clear Ran");
    contentPanel.removeAll();
    contentPanel.repaint();
}

/**
 * Adds the Login Screen.
 */
public void login() {
    System.out.println("Login Ran");
    contentPanel.add(loginPanel);
    contentPanel.repaint();
}

/**
 * Adds the menu.
 */
public void menu() {
    System.out.println("Menu Ran");
    mainPanel.sidePanel.add(menuPanel);
    menuPanel.repaint();
    mainPanel.repaint();
    mainPanel.sidePanel.repaint();
}

}

以下是面板的代码，其中大部分是由netbeans设计编辑器自动生成的。所以它很难看（对不起）

公共类MenuPanel扩展了javax.swing.JPanel {

/**
 * Creates new form MenuPanel
 */
public MenuPanel() {
    initComponents();
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    jLabel1 = new javax.swing.JLabel();
    jSeparator1 = new javax.swing.JSeparator();
    jLabel2 = new javax.swing.JLabel();
    baggageButton = new javax.swing.JLabel();

    jLabel1.setBackground(new java.awt.Color(204, 204, 204));
    jLabel1.setFont(new java.awt.Font("Tahoma", 0, 13)); // NOI18N
    jLabel1.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
    jLabel1.setText("Menu");

    jSeparator1.setBackground(new java.awt.Color(204, 204, 204));

    baggageButton.setFont(new java.awt.Font("Tahoma", 0, 12)); // NOI18N
    baggageButton.setText("Baggage");

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
    this.setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jSeparator1)
                .addComponent(jLabel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(baggageButton, javax.swing.GroupLayout.PREFERRED_SIZE, 80, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jLabel2, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
            .addContainerGap())
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(0, 0, 0)
            .addComponent(jSeparator1, javax.swing.GroupLayout.PREFERRED_SIZE, 4, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addComponent(baggageButton, javax.swing.GroupLayout.PREFERRED_SIZE, 53, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(18, 18, 18)
            .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 53, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );
}// </editor-fold>                        

// Variables declaration - do not modify                     
private javax.swing.JLabel baggageButton;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JSeparator jSeparator1;
// End of variables declaration                   
}

只是为了澄清，方法菜单是从另一个类调用的。

Answer 1

如果要向已经可见的面板添加组件，则需要调用validate()。

public void menu() {
    System.out.println("Menu Ran");
    mainPanel.sidePanel.add(menuPanel);

    mainPanel.sidePanel.validate();  // try this

    menuPanel.repaint();
    mainPanel.repaint();
    mainPanel.sidePanel.repaint();
}

Answer 2

（这个答案是错误的，但随后的评论确实有助于理解为什么@ whiskeyspider的答案是正确的）

在此代码中：

mainFrame.add(mainPanel);
mainPanel.add(contentPanel);

mainFrame.setVisible(true);
contentPanel.add(loginPanel);

您未在任何地方添加menuPanel。它在menu()方法中添加（太晚），但未被调用。

JPanel没有显示组件

2 个答案: