为什么 JLabel 或 JButton 在运行 GUI 时不显示？

Question

我一直在尝试多种解决方案，但其中 none 似乎有效。在构造函数中，有一个默认值 initComponents() 我无法更改。所以我创建了第二个方法 myComponents()。 class 我正在使用扩展 JFrame 所以我不需要在任何初始化程序中创建另一个框架。我创建了一个带有垂直 Boxlayout、2 个标签、1 个文本字段和 1 个按钮的 JPanel。我将面板添加到框架，然后将所有组件添加到面板，然后打包所有内容。

我不确定为什么在运行时除了框架什么都没有显示。

import javax.swing.BoxLayout;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

/**
 *
 * @author gpbli
 */
public class MAINFRAME extends javax.swing.JFrame {

    /**
     * Creates new form MAINFRAME
     */
    //MAINFRAME frame = new MAINFRAME();
    JPanel homescreen = new JPanel();

    JLabel numOfIngredLabel = new JLabel();
    JTextField numOfIngred = new JTextField();
    JButton okButton = new JButton();
    JLabel logo = new JLabel();

    ImageIcon img = new ImageIcon("logo_resized.png");
    public MAINFRAME() {
        initComponents();
        myComponents();
    }
    public void myComponents(){
        BoxLayout box = new BoxLayout(homescreen,BoxLayout.Y_AXIS);
        homescreen.setLayout(box);
    
    numOfIngredLabel.setText("How many Ingredients");
    numOfIngred.setText("");
    okButton.setText("OK");
    logo.setText(" ");
    logo.setIcon(img);
    
    add(homescreen);
    homescreen.add(logo);
    homescreen.add(numOfIngredLabel);
    homescreen.add(numOfIngred);
    homescreen.add(okButton);
    
    numOfIngredLabel.setVisible(true);
    numOfIngred.setVisible(true);
    okButton.setVisible(true);
    logo.setVisible(true);
    
    pack();
    revalidate();
    
    
}
/**
 * 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() {

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 400, Short.MAX_VALUE)
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 300, Short.MAX_VALUE)
    );

    pack();
}// </editor-fold>                        

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(MAINFRAME.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(MAINFRAME.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(MAINFRAME.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(MAINFRAME.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    
    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new MAINFRAME().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
// End of variables declaration                   
}

Answer 1

initComponents() 的出现表明 IDE 期望程序员使用 GUI 生成器，而 myComponents() 是程序员控制 GUI 构造并通过手.

使用一个或另一个。我总是使用后者，它不需要扩展 JFrame 。事实上，在 JPanel 中创建 GUI 的主视图并将该单个组件添加到 JFrame 是我们通常推荐的方式。

注：另见accepted answer to: Netbeans GUI editor generating its own incomprehensible code

为什么 JLabel 或 JButton 在运行 GUI 时不显示？

Why won't the JLabels or JButtons show up when running the GUI?

java

swing

jpanel

jframe

为什么 JLabel 或 JButton 在 运行 GUI 时不显示？

Why won't the JLabels or JButtons show up when running the GUI?

java

swing

jpanel

jframe

为什么 JLabel 或 JButton 在运行 GUI 时不显示？