单击后，Java按钮消失

Question

I'm trying to add a button using an JOptionPane in another button, but after I clicked the original button just keeps disappearing.

I've tried adding the JPanel manually instead of using 'handPanelNPC.getHandPanel()' by iterating through the handPanel.buttons but it stil wont work. I've checked the ArrayList size and it is already inserted properly.

LayoutTesting.java

public class LayoutTesting extends JFrame{
    HandPanel handPanelNPC = new HandPanel();

    public LayoutTesting(HandPanel handPanel, int type){
        Container pane = getContentPane();

        if (type==1){
            handPanelNPC = handPanel;
        }
        pane.setLayout(new BorderLayout());
        pane.add(handPanelNPC.getHandPanel(), BorderLayout.NORTH);
        validate();
        repaint();
    }

    public LayoutTesting(){
        Container pane = getContentPane();

        pane.setLayout(new BorderLayout());
        pane.add(handPanelNPC.getHandPanel(), BorderLayout.NORTH);
    }
}

HandPanel.java

public class HandPanel implements ActionListener{   
    JFrame frame = null;
    JPanel panel = new JPanel();
    ArrayList<JButton> buttons = new ArrayList<JButton>();

    public HandPanel(){
        addNewButton();
        panel.setLayout(new FlowLayout());
        panel.add(buttons.get(0));
    }

    public JComponent getHandPanel(){
        panel = new JPanel();
        for(int i=0; i<buttons.size(); i++){
            JButton button = buttons.get(i);
            panel.add(button);
        }

        return panel;
    }

    public void addNewButton(){
        JButton button = new JButton();
        button.setPreferredSize(new Dimension(40,58));
        button.addActionListener(this);

        buttons.add(button);
    }

    public void actionPerformed(ActionEvent e) {
      String[] options = {"Summon", "Set", "Add Card"}; 

      int messageType = JOptionPane.QUESTION_MESSAGE;
      int code = JOptionPane.showOptionDialog(
        frame, 
        "What would you like to do?", 
        "Card Name", 
        0, messageType, null, 
        options, options[1]);

      if (code==2){
        addNewButton();
        LayoutTesting frame = new LayoutTesting(this, 1);
      } 
    }
}

Main.java

public class Main extends JFrame{
    public static void main(String[] args){
         LayoutTesting frame = new LayoutTesting();

         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.setSize(400, 300);
         frame.setVisible(true);
     }
}

Answer 1

You have too many odd things happening in your code to give a simple answer.

Try debugging your own code by looking at this line in HandPanel.java:

LayoutTesting frame = new LayoutTesting(this, 1);

What does it really do? Now remove that line and the button will not disappear. Now try and work out what that line was doing, and why the button disappeared.

Also 'panel.add(buttons.get(0));' does nothing because there is never a button in the array when you make that call (You add the button afterwards in another method).

Here is a rough working demo that lets you add as many new cards as you want to the first frame, and each card has a button that will let you summon a new card.

public class LayoutTesting extends JFrame{
    Container pane;

    //Add card when button is pressed:
    public void addCard(){
        Container card = new JPanel();
        card.setBackground(Color.red);
        JButton newButton = addNewButton();
        newButton.setBackground(Color.red);
        card.add(newButton);
        pane.add(card);
        revalidate();
        repaint();
    }

    //Setup window and add button:
    public LayoutTesting(){
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(400, 300);
        setVisible(true);
        setLayout(new FlowLayout());
        pane = new JPanel();
        pane.setLayout(new GridBagLayout());
        JButton firstButton = addNewButton();
        firstButton.setBackground(Color.green);
        add(pane);
        add(firstButton);   
    }

    //Create button and action listener:
    public JButton addNewButton(){
        JButton button = new JButton();
        button.setPreferredSize(new Dimension(40, 58));
        button.addActionListener(new java.awt.event.ActionListener(){
        @Override
        public void actionPerformed(java.awt.event.ActionEvent evt){
            buttonAction(evt);
        }
        });
        return button;
    }

    //Action fer each button:
    public void buttonAction(ActionEvent e) {
        String[] options = {"Summon", "Set", "Add Card"};

        int messageType = JOptionPane.QUESTION_MESSAGE;
        int code = JOptionPane.showOptionDialog(
        this, 
        "What would you like to do?", 
        "Card Name", 
        0, messageType, null, 
        options, options[1]);

        if (code==2){
        addCard();
        }
    }
}