Java-调用嵌套类中的方法，特别是ActionListener

Question

Edit: Solved, I wasn't using 'validate()' after adding components.

I have a GUI class structured something like this (this is a very basic representation of my code):

Edit: here's my full code

package source;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

public class Gui extends JFrame 
{
    public String[] list1 = {"equation1","equation2","equation3","equation4", "equation5"};
    public JOptionPane opt1;
    private JButton custom;
    private JTextField[] tf;
    public HandlerClass2 itemhandler = new HandlerClass2();
    private JList list;
    private static int index = 0;
    private static int lastlistindex = 0;
    private JPanel buttonpanel;
    private JPanel buttonpanel2[] = new JPanel[3];
    private JPanel listpanel[] = new JPanel[4];
    private JPanel checkpanel;
    private JCheckBox checkboxes[];
    private SpringLayout layout;
    public Container contentPane;
    private JButton but;

public Gui()
{
    super("Physics Helper v0.1");
    setBackground(Color.DARK_GRAY);

    layout = new SpringLayout();

    contentPane = getContentPane();
    contentPane.setLayout(layout);

    displayPortal();
}

public void displayPortal()
{
    Icon a = new ImageIcon(getClass().getResource("button.png"));    
    Icon b = new ImageIcon(getClass().getResource("button2.png")); 
    custom = new JButton("", a);
    custom.setRolloverIcon(b);

    buttonpanel = new JPanel();
    buttonpanel.setBackground(Color.GRAY);
    buttonpanel.add(custom);
    contentPane.add(buttonpanel);

    layout.putConstraint(SpringLayout.WEST, buttonpanel, 5, SpringLayout.WEST, contentPane);
    layout.putConstraint(SpringLayout.EAST, buttonpanel, -5, SpringLayout.EAST, contentPane);
    layout.putConstraint(SpringLayout.NORTH, buttonpanel, 5, SpringLayout.NORTH, contentPane);

    custom.addActionListener(new HandlerClass());

}

public void displayButton(String s)
{
    but = new JButton(s);

    buttonpanel2[index] = new JPanel();
    buttonpanel2[index].setBackground(Color.GRAY);
    buttonpanel2[index].add(but);

    contentPane.add(buttonpanel2[index]);

    layout.putConstraint(SpringLayout.SOUTH, buttonpanel2[index], -5, SpringLayout.SOUTH, contentPane);

    if (index < 1)
    {
        layout.putConstraint(SpringLayout.WEST, buttonpanel2[index], 5, SpringLayout.WEST, contentPane);
    }
    else
    {
        layout.putConstraint(SpringLayout.WEST, buttonpanel2[index], 5, SpringLayout.EAST, buttonpanel2[index - 1]); 
    }

    index++;
}

public void displayList(String[] t)
{
    list = new JList(t);
    list.setVisibleRowCount(8);
    list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
    add(new JScrollPane(list));

    listpanel[lastlistindex] = new JPanel();
    listpanel[lastlistindex].setBackground(Color.GRAY);
    listpanel[lastlistindex].add(list);

    contentPane.add(listpanel[lastlistindex]);

    layout.putConstraint(SpringLayout.NORTH, listpanel[lastlistindex], 5, SpringLayout.SOUTH, buttonpanel);

    if (lastlistindex < 1)
    {
        layout.putConstraint(SpringLayout.WEST, listpanel[lastlistindex], 5, SpringLayout.WEST, contentPane);
    }
    else
    {
        layout.putConstraint(SpringLayout.WEST, listpanel[lastlistindex], 5, SpringLayout.EAST, listpanel[lastlistindex - 1]);
    }

    lastlistindex++;
}

public void displayInputValues(String[] p)
{   
    checkboxes = new JCheckBox[p.length];

    GridLayout gridlayout = new GridLayout(p.length, 2);
    tf = new JTextField[p.length];

    checkpanel = new JPanel();
    checkpanel.setBackground(Color.GRAY);
    checkpanel.setLayout(gridlayout);

    for (int b = 0; b < p.length; b++)
    {
        checkboxes[b] = new JCheckBox(p[b]);
        checkpanel.add(checkboxes[b]);

        tf[b] = new JTextField("", 9);
        checkpanel.add(tf[b]);
        tf[b].setFont(new Font("Serif", Font.PLAIN, 14));
    }

    contentPane.add(checkpanel);

    layout.putConstraint(SpringLayout.EAST, checkpanel, -5, SpringLayout.EAST, contentPane);
    layout.putConstraint(SpringLayout.SOUTH, checkpanel, -5, SpringLayout.SOUTH, contentPane);
}

private class HandlerClass implements ActionListener
{

    public void actionPerformed(ActionEvent event)
    {            
        displayButton("Back");
        displayButton("Next");

        displayList(list1);
    }
}    

My main method is contained within another class, and works fine.

My question is how can I call the "displayButton" method in the actionPerformed method? I've tried a few tips already, such as calling it with "Gui.this.displayButton("Press me!").

I have tested every other aspect of my code, and this seems to be the only problem.

I get no errors when I run the code.

If needs be I can post the full class, but I think this problem lies in trying to call these methods.

What's your opinion?

Answer 1

Calling the method works fine, nothing fancy needed

You need to add an instance of your HandlerClass to a GUI control, such as a JButton , which will trigger the method when clicked. That is the whole point of ActionListeners (and listeners in general). For example:

myJButton.addActionListener(new HandlerClass());

A working example based on your code:

public class Gui extends JFrame
{
    public Gui()
    {
        super("Physics Helper v0.1");
        JButton b = new JButton("Press me!");
        b.addActionListener(new HandlerClass());
        add(b);
        pack();
        setVisible(true);
    }

    public void displayButton(String s)
    {
        System.out.println(s);
    }

    private class HandlerClass implements ActionListener
    {
        public void actionPerformed(ActionEvent event)
        {
            displayButton("Press me!");
        }
    }

    public static void main(String[] args)
    {
        new Gui();
    }
}

Answer 2

Adding/removing components in a Container at runtime is possible, but not necessarily good practice. If you want to display different contents based on user selections in your GUI, consider using a CardLayout layout manager, which handles all the runtime details automatically.

Jim S.

Answer 3

Your code should work finely. You will have to addActionListener to a component.

Else

You could write the displayButton method within the Handler Class. Then you would have to simply call the method as it is with access to the previous class's members.

Answer 4

The quick and dirty option is to make the displayButton call static.

Then issue is more a design one than anything else. I'd suggest you ask yourself why you want your action listener to call a method in the owning object.