在 JPanel 中动态添加 JLabel（重新验证不起作用）

Question

I have a method that tries to add labels dynamically in JPanel in the PackingByVolDialog class:

public static void addContent( String content, String container) {

        contentPanel = new JPanel();
        changingLabel = new JLabel(); 
        changingLabel.setText(container+"\n"+content);
        contentPanel.add(changingLabel);
        contentPanel.revalidate();
        contentPanel.repaint();
        dialog.add(contentPanel);
    }

and in an other class , I call the addContent method as follows:

for (int u=0; u<containers.size()-1; u++) {

          PackingByVolDialog.addContent(content, container);

                 } //end for

This is the MCVE (?) I was asked to make ( I hope it's correct and helpful)

public class VolDialog extends JDialog {

    private static JLabel label = new JLabel() ;
    private static JPanel contentPanel = new JPanel();
    private static VolDialog dialog = new VolDialog(); 


  public static void main(String[] args) {
        try {
             dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
             dialog.add(contentPanel);
             dialog.revalidate();
             dialog.repaint();
            dialog.setVisible(true);
    } catch (Exception e) {
        e.printStackTrace();
    }
}


 public static void addContent( String text) {

    contentPanel = new JPanel();
    changingLabel = new JLabel(); 
    changingLabel.setText(text);
    contentPanel.add(changingLabel);
    }


 public class content {

       for (int u=0; u<N; u++) {

               VolDialog.addContent("text");

             } //end for
          }

even when using repaint and revalidate of the JPanel, only the last output is displayed in the window.

Does anyone know where the problem is?

Answer 1

The project I am doing is too big and complicated

Which is why you always need to create and post an MCVE when asking a question. We don't have time to look at and understand your entire project. It is up to you to understand the problem you are asking about and then simplify the code to duplicate the problem. Many times when you do this you will find your problem. If not, then you have a simple piece of code to post.

it is not an easy task.

Once you do it a couple of times, like anything in life, it becomes easier and easier.

I was in a rush because I don't have time at all to write new codes

Well you should still produce well structured and designed code. It takes no more time to create an MVCE properly using normal Swing coding conventions.

For example:

1. You should not be extending JDialog. All you are doing is adding components to the dialog so in the main() method you just create the dialog.

2. You should not be using static variables and methods. This indicates poor design of the code.

3. Class names should start with an upper case character

4. Your code doesn't compile.

5. You never create a new instance of the "content" class, so the addContent(...) method is never invoked. So this mean you never even tested the code you posted.

When you ask the question YOU need to take the time to do things properly and give us the information we need to solve the problem.

only the last output is displayed in the window.

The default layout manager of Swing frames and dialogs is a BorderLayout . You can only add a single component to the "CENTER" of the BorderLayout (which is the default when you don't specify a constraint).

So basically you need to change the layout manager of the dialog. Try changing:

dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
dialog.setLayout( new FlowLayout() );

to see the difference.

If you need more help then post a proper MCVE. One that actually compiles and is well designed.