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Assigning current JPanel to new instance of JPanel but does not refresh

I have sub-classed JPanel to provide a generic JPanel container that contains options for a filter selected from a JComboBox.
When the JComboBox is changed from one filter to another, I have a switch statement that checks which filter is now selected and reassigns the "options" JPanel to a new instance of the options class associated with that filter:
public void setFilterOptions(String choice){
switch(choice){
case "Gaussian": options = new GaussianFilterOptions();break;
case "Sobel": options = new SobelFilterOptions();System.out.println("?");break;
}
}
The problem is that the JPanel "options" does not get refreshed in the GUI after setFilterOptions is called. Whichever filter is set to show by default appears upon startup and remains even if I switch the JComboBox selection. I have tried repainting, revalidating, and validating "options" as well as the JPanel containing "options" and the JFrame enclosing the entire application.
I added print statements in each case to verify that they were working when the combo box is switched and not falling through, so I'm sure that is not the problem.

You're confusing variable with object. You have likely originally placed a JPanel object that options referred to into your GUI, but understand, you didn't place the options variable into the GUI, but rather (and again) the JPanel object that it referred to into the GUI.
If later you change the JPanel that the options variable refers to, this will have no effect on the GUI, since it still holds the same original JPanel object that it held before. If you want to change the JPanel displayed, you have to do that directly by swapping out JPanels in the GUI. This is best accomplished by using a CardLayout.
e.g.,
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class SwapPanels extends JPanel {
private static final String GAUSSIAN = "Gaussian";
private static final String SOBEL = "Sobel";
private static final String[] FILTER_OPTIONS = {GAUSSIAN, SOBEL};
private CardLayout cardLayout = new CardLayout();
private JPanel cardHolderPanel = new JPanel(cardLayout);
private JPanel gaussianPanel = new JPanel();
private JPanel sobelPanel = new JPanel();
private JComboBox<String> filterCombo = new JComboBox<>(FILTER_OPTIONS);
public SwapPanels() {
JPanel comboPanel = new JPanel();
comboPanel.add(filterCombo);
filterCombo.addActionListener(new ComboListener());
gaussianPanel.add(new JLabel("Gaussian Filtering Done Here"));
sobelPanel.add(new JLabel("Sobel Filtering Done Here"));
cardHolderPanel.add(gaussianPanel, GAUSSIAN);
cardHolderPanel.add(sobelPanel, SOBEL);
int gap = 50;
cardHolderPanel.setBorder(BorderFactory.createEmptyBorder(gap, gap, gap, gap));
setLayout(new BorderLayout());
add(cardHolderPanel, BorderLayout.CENTER);
add(comboPanel, BorderLayout.PAGE_END);
}
private class ComboListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
String key = (String) filterCombo.getSelectedItem();
cardLayout.show(cardHolderPanel, key);
}
}
private static void createAndShowGui() {
SwapPanels mainPanel = new SwapPanels();
JFrame frame = new JFrame("SwapPanels");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}

Also you could do it like this instead of the switch
public void setFilterOptions(String choice){
options = (choice.equals("Gaussian"))? new GaussianFilterOptions():
new SobelFilterOptions();
}
}

How to display one Jframe at a time? [duplicate]

I'm trying to make a little game that will first show the player a simple login screen where they can enter their name (I will need it later to store their game state info), let them pick a difficulty level etc, and will only show the main game screen once the player has clicked the play button. I'd also like to allow the player to navigate to a (hopefully for them rather large) trophy collection, likewise in what will appear to them to be a new screen.
So far I have a main game window with a grid layout and a game in it that works (Yay for me!). Now I want to add the above functionality.
How do I go about doing this? I don't think I want to go the multiple JFrame route as I only want one icon visible in the taskbar at a time (or would setting their visibility to false effect the icon too?) Do I instead make and destroy layouts or panels or something like that?
What are my options? How can I control what content is being displayed? Especially given my newbie skills?

A simple modal dialog such as a JDialog should work well here. The main GUI which will likely be a JFrame can be invisible when the dialog is called, and then set to visible (assuming that the log-on was successful) once the dialog completes. If the dialog is modal, you'll know exactly when the user has closed the dialog as the code will continue right after the line where you call setVisible(true) on the dialog. Note that the GUI held by a JDialog can be every bit as complex and rich as that held by a JFrame.
Another option is to use one GUI/JFrame but swap views (JPanels) in the main GUI via a CardLayout. This could work quite well and is easy to implement. Check out the CardLayout tutorial for more.
Oh, and welcome to stackoverflow.com!

Here is an example of a Login Dialog as #HovercraftFullOfEels suggested.
Username: stackoverflow Password: stackoverflow
import java.awt.*;
import java.awt.event.*;
import java.util.Arrays;
import javax.swing.*;
public class TestFrame extends JFrame {
private PassWordDialog passDialog;
public TestFrame() {
passDialog = new PassWordDialog(this, true);
passDialog.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new TestFrame();
frame.getContentPane().setBackground(Color.BLACK);
frame.setTitle("Logged In");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
}
});
}
}
class PassWordDialog extends JDialog {
private final JLabel jlblUsername = new JLabel("Username");
private final JLabel jlblPassword = new JLabel("Password");
private final JTextField jtfUsername = new JTextField(15);
private final JPasswordField jpfPassword = new JPasswordField();
private final JButton jbtOk = new JButton("Login");
private final JButton jbtCancel = new JButton("Cancel");
private final JLabel jlblStatus = new JLabel(" ");
public PassWordDialog() {
this(null, true);
}
public PassWordDialog(final JFrame parent, boolean modal) {
super(parent, modal);
JPanel p3 = new JPanel(new GridLayout(2, 1));
p3.add(jlblUsername);
p3.add(jlblPassword);
JPanel p4 = new JPanel(new GridLayout(2, 1));
p4.add(jtfUsername);
p4.add(jpfPassword);
JPanel p1 = new JPanel();
p1.add(p3);
p1.add(p4);
JPanel p2 = new JPanel();
p2.add(jbtOk);
p2.add(jbtCancel);
JPanel p5 = new JPanel(new BorderLayout());
p5.add(p2, BorderLayout.CENTER);
p5.add(jlblStatus, BorderLayout.NORTH);
jlblStatus.setForeground(Color.RED);
jlblStatus.setHorizontalAlignment(SwingConstants.CENTER);
setLayout(new BorderLayout());
add(p1, BorderLayout.CENTER);
add(p5, BorderLayout.SOUTH);
pack();
setLocationRelativeTo(null);
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
jbtOk.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (Arrays.equals("stackoverflow".toCharArray(), jpfPassword.getPassword())
&& "stackoverflow".equals(jtfUsername.getText())) {
parent.setVisible(true);
setVisible(false);
} else {
jlblStatus.setText("Invalid username or password");
}
}
});
jbtCancel.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
setVisible(false);
parent.dispose();
System.exit(0);
}
});
}
}

I suggest you insert the following code:
JFrame f = new JFrame();
JTextField text = new JTextField(15); //the 15 sets the size of the text field
JPanel p = new JPanel();
JButton b = new JButton("Login");
f.add(p); //so you can add more stuff to the JFrame
f.setSize(250,150);
f.setVisible(true);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Insert that when you want to add the stuff in. Next we will add all the stuff to the JPanel:
p.add(text);
p.add(b);
Now we add the ActionListeners to make the JButtons to work:
b.addActionListener(this);
public void actionPerforemed(ActionEvent e)
{
//Get the text of the JTextField
String TEXT = text.getText();
}
Don't forget to import the following if you haven't already:
import java.awt.event*;
import java.awt.*; //Just in case we need it
import java.x.swing.*;
I hope everything i said makes sense, because sometimes i don't (especially when I'm talking coding/Java) All the importing (if you didn't know) goes at the top of your code.

Instead of adding the game directly to JFrame, you can add your content to JPanel (let's call it GamePanel) and add this panel to the frame. Do the same thing for login screen: add all content to JPanel (LoginPanel) and add it to frame. When your game will start, you should do the following:
Add LoginPanel to frame
Get user input and load it's details
Add GamePanel and destroy LoginPanel (since it will be quite fast to re-create new one, so you don't need to keep it memory).

is it possible to point to a particular JPanel

I have this program in which I'm using CardLayout. I have different panels with different attributes. I have a button called "Enter" that I decided to reuse on every panel, however each panel performs a different operation when the button is clicked. Is there a way to say, when button is clicked but I am at a specific panel, then do this. How can I point directly to a panel?

First thing you must consider is: You can't add one button to many panels, every panel should have it's own component(s).
If you add one button to many panels say :
JButton b = new JButton("Button");
//....
pan1.add(b);
pan2.add(b);
pan3.add(b);
In such case, the button will be added to the last panel means pan3, the other won't show the button.
Second, I would like to mention a #trashgod's good example from comments, and also in case confusing, look at this example:
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class CardLayoutDemo extends JFrame implements ActionListener {
private CardLayout cardLayout;
private JButton pan1,pan2;
private JPanel mainPanel;
public CardLayoutDemo(){
cardLayout = new CardLayout();
mainPanel = new JPanel(cardLayout);
JPanel p1 = new JPanel();
JPanel p2 = new JPanel();
pan1 = new JButton("To Second Panel");
pan2= new JButton ("To First Panel");
pan1.addActionListener(this);
pan2.addActionListener(this);
p1.setBackground(Color.green);
p2.setBackground(Color.BLUE.brighter());
p1.add(pan1);
p2.add(pan2);
mainPanel.add(p1,"1");
mainPanel.add(p2,"2");
cardLayout.show(mainPanel, "1");
add(mainPanel);
setDefaultCloseOperation(3);
setLocationRelativeTo(null);
setVisible(true);
pack();
}
#Override
public void actionPerformed(ActionEvent ev){
if(ev.getSource()==pan1)
cardLayout.show(mainPanel, "2");
else if(ev.getSource()==pan2)
cardLayout.show(mainPanel, "1");
}
public static void main(String...args){
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new CardLayoutDemo().setVisible(true);
}
});
}
}

You can let the panel assign an ActionListener to the button each time the card is created. That way the constructor for a specific panel can determine what the functionality of the button will be.

Using Actionlistener to create new frame with JRadioButtons

Hi I'm having some trouble creating an actionlistener which creates a new frame with JRadioButtons used as selections.
Ultimately it will be a flashcard quiz program I am creating for fun.
Here's what where I am stuck:
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class FlashCard extends JFrame {
private ImageIcon myIcon = new ImageIcon("src/Resources/DNA.png");
public FlashCard(){
//Consider using CardLayout format for flashcards.
setLayout(new GridLayout(1, 4, 5, 5));
JButton startButton = new JButton("Begin");
add(startButton);
startButton.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
//Execute when button is pressed THIS IS THE PART WHERE I AM STUCK
JFrame frameAction = new JFrame();
frameAction.setTitle("Questions");
frameAction.setSize(350, 150);
frameAction.setLocationRelativeTo(null);
frameAction.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frameAction.setVisible(true);
frameAction.
// JRadioButton jrb1 = new JRadioButton("Student", true);
// jrb1.setForeground(Color.RED);
// jrb1.setBackground(Color.WHITE);
// jrb1.setMnemonic('S');
//
// ButtonGroup group = new ButtonGroup();
// add(jrb1);
}
});
}
and here is my main method:
public static void main(String[] args){
//Create a frame and set its properties.
JFrame frame = new FlashCard();
frame.setTitle("Genetics FlashCard Quiz");
frame.setSize(350,150);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
//Create a second frame for when the user
// clicks begin.
JFrame question = new JFrame();
}

Given that both your JFrames are the same size & dimensions, your other idea (in the code) of using CardLayout was the correct one. Currently your 2nd frame appears over the first giving you the overhead of managing the latter as it is still accessible. If you use CardLayout you will be able to easily navigate between multiple flashcard panels while maintaining a single interaction area for the user.
See:
How to Use CardLayout
CardLayout Example

Button is filling up the entire cell in GridLayout, Java

I'm a beginner and doing my homework. My button is filling up the whole cell in the gridLayout. I've read about GridBagLayout but my book doesn't mention anything about it so I think there's just an error with my current code. The teacher has been trying to help me but we can't figure it out so I thought I would try here. Any help would be appreciated! Here is what I have:
package riddle;
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class Riddle implements ActionListener {
private final String LABEL_TEXT = "Why did the chicken cross the road?";
JFrame frame;
JPanel contentPane;
JLabel label, label1;
JButton button;
JButton button1;
private static int i;
public Riddle() {
/* Create and set up the frame */
frame = new JFrame(LABEL_TEXT);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
/* Create a content pane with a GridLayout and empty borders */
contentPane = new JPanel();
contentPane.setLayout(new GridLayout(0, 2, 10, 5));
/* Create and add label that is centered and has empty borders */
label = new JLabel("Why did the chicken cross the road?");
label.setAlignmentX(JButton.LEFT_ALIGNMENT);
label.setBorder(BorderFactory.createEmptyBorder(20, 50, 20, 50));
contentPane.add(label);
label1 = new JLabel(" ");
label1.setAlignmentX(JButton.LEFT_ALIGNMENT);
label1.setBorder(BorderFactory.createEmptyBorder(20, 50, 20, 50));
contentPane.add(label1);
/* Create and add button that is centered */
button = new JButton("Answer");
button.setAlignmentX(JButton.RIGHT_ALIGNMENT);
button.setActionCommand("Show Answer");
button.addActionListener(this);
contentPane.add(button);
/* Add content pane to frame */
frame.setContentPane(contentPane);
/* Size and then display the frame */
frame.pack();
frame.setVisible(true);
}
/** Handle button click action event
* pre:
* post: clicked button shows answer
*/
public void actionPerformed(ActionEvent event) {
String eventName = event.getActionCommand();
if (eventName.equals("Show Answer")) {
label1.setText("To get to the other side. ");
button.setText("Answer");
button.setActionCommand("Answer");
}
}
/**
* Create and show the GUI
*/
private static void runGUI() {
JFrame.setDefaultLookAndFeelDecorated(true);
Riddle greeting = new Riddle();
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
runGUI();
}
});
}
}

Here's a quote from the Swing tutorial about GridLayout:
A GridLayout object places components in a grid of cells. Each
component takes all the available space within its cell, and each cell
is exactly the same size.
If your book doesn't tell such an important thing, it's a bad book, and I would advise using the Swing tutorial instead. I'm astonished your teacher hasn't been able to tell you that.
If this behavior is not the one you want, choose another layout manager. The Swing tutorial has a guide for all standard ones.