将 JPanel 添加到 JFrame 不起作用

Question

How to add JPanel to JFrame in other class?? I've tried with this code, but when I compile it, it didn't show any component in MyFrame.java (the label "Hello World"). What's wrong with my code?

(Button in MainFrame.java called the MyFrame.java )

Here's the code:

MyPanel.java (contains button and label)

public class MyPanel extends javax.swing.JPanel {

    public MyPanel() {
        initComponents();
        myLabel.setText("Hello World");
    }
}

MyFrame.java

public class MyFrame extends javax.swing.JFrame {

    MyPanel myPanel = new MyPanel();

    public MyFrame() {
        initComponents();
        this.add(myPanel);
    }
}

MainFrame.java

public class MainFrame extends javax.swing.JFrame {

    public MainFrame() {
        initComponents();
    }

    private void btnCallFrameActionPerformed(java.awt.event.ActionEvent evt) {                                         
        new MyFrame().setVisible(true);
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new MainFrame().setVisible(true);
            }
        });
    }
}       

Answer 1

I don't know what you have done in initComponents method. So I have changed your code a little bit.

public class MyPanel extends javax.swing.JPanel {

    public MyPanel() {
        initComponents();
        //I don't know what you did in initComponents(); so I ve changed the layout to be sure that you didn't use null layout. 
        this.setLayout(new BorderLayout());

        JLabel myLabel = new JLabel();
        myLabel.setText("Hello World");

       //adding the label in MyPanel 
       this.add(myLabel);
    }
}

public class MyFrame extends javax.swing.JFrame {

    MyPanel myPanel = new MyPanel();

    public MyFrame() {
        initComponents();
        // added because of the former reason
        this.setLayout(new BorderLayout());
        this.add(myPanel);
    }
}

I hope you are sure that you can call the btnCallFrameActionPerformed method with some button.