Develop Reference

Gui Interactions

This is my first time creating a Gui and I'm stumped on how to create interactions.
I'm trying to implement a single selection mode when the combobox is on single, and multiple when it's placed on multiple. I placed them on the multi line comment.
Any ideas?
//Interactions
//When “Single” is selected then the JList changes so only one item
can be selected.
//When “Multiple” is selected, the JList changes so multiple items can
be selected
//When a country, or multiple countries, is selected the JLabel
changes to reflect the new selections
public class GuiTest {
public static String[] Countries = {"Africa", "Haiti", "USA", "Poland", "Russia", "Canada", "Mexico", "Cuba"};
public static String[] Selection = {"Single", "Multiple"};
JPanel p = new JPanel();
JButton b = new JButton("Testing");
JComboBox jc = new JComboBox(Selection);
JList jl = new JList(Countries);
private static void constructGUI() {
JFrame.setDefaultLookAndFeelDecorated(true);
JFrame frame = new JFrame();
frame.setTitle("Countries Selection");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// add a JLabel that says Welcome
JLabel label = new JLabel("Selected Items:");
frame.add(label);
frame.pack();
JComboBox jc = new JComboBox(Selection);
frame.add(jc);
frame.pack();
frame.setVisible(true);
JList jl = new JList(Countries);
frame.add(jl);
frame.pack();
JComponent panel = new JPanel();
panel.setLayout(new FlowLayout());
panel.add(new JLabel("Choose Selection Mode:"));
panel.add(jc);
frame.add(panel, BorderLayout.NORTH);
frame.add(jl, BorderLayout.WEST);
frame.add(label, BorderLayout.SOUTH);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
constructGUI();
}
});
}
}

you should start adding the modes to the ComboBox:
comboBoxCategoria.addItem("Single",0);
comboBoxCategoria.addItem("Multiple",1);
then add a ActionListener to your ComboBox to modify the list selection mode
jc.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
if(jc.getSelectedItem().equals("Single")){
jl.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
}else{//must equals
jl.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
}
}
});
finally add a MouseListener on the list to detect changes on the list selections and change the JLabel to reflect the new selections
jl.addMouseListener(new MouseAdapter() {
#Override
public void mouseReleased(MouseEvent e) {
label.setText(list.getSelectedValuesList().toString());
}
});
edit: you should also add a KeyListener to update the label since the selection can be changed via arrow keys
jl.addKeyListener(new KeyAdapter() {
#Override
public void keyReleased(KeyEvent e) {
label.setText(list.getSelectedValuesList().toString());
}
});

It would be something like this:
jc.addActionListener((evt) -> {
if ("Single".equals(jc.getSelectedItem())) {
jl.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
int[] sel = jl.getSelectedIndices();
if (sel != null && sel.length > 1) {
jl.setSelectedIndex(sel[0]);
}
} else {
jl.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
}
});
jl.addListSelectionListener((evt) -> {
StringBuilder buf = new StringBuilder();
for (Object o: jl.getSelectedValuesList()) {
if (buf.length() > 0) {
buf.append(", ");
}
buf.append(o);
}
label.setText(buf.toString());
});
jc.setSelectedItem("Single");

How to use CardLayout with multiple JButtons?

I need to make a GUI that asks the users for details and then save them in a linked list. I wanted to use the CardLayout to switch from one frame to another, which is something I'm doing for the first time. I have done probably less half of what I need to do and here I am quite lost in this part. The code below compiles and executes but when I click the buttons, the desired change does not happen . What could be wrong?
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MyDatabaseWindow extends JPanel{
public static final String FRONT_PAGE = "Front Page";
public static final String BROWSE_MEMORIES = "Browse Memories";
public static final String ADD_EDIT = "Add Edit";
public static final String VIEW_MEMORY = "View Memory";
public static void createAndShowGUI() {
final MyDatabaseWindow mdbw = new MyDatabaseWindow();
JPanel buttonPanel = new JPanel();
buttonPanel.setLayout(null);
final JButton addButton = new JButton("Add");
final JButton editButton = new JButton("Edit");
final JButton deleteButton = new JButton("Delete");
final JButton browseButton = new JButton("Browse");
final JButton searchButton = new JButton("Search");
addButton.setBounds(100, 400, 100, 100);
editButton.setBounds(200, 400, 100, 100);
deleteButton.setBounds(300, 400, 100, 100);
browseButton.setBounds(400, 400, 100, 100);
searchButton.setBounds(500, 400, 100, 100);
buttonPanel.add(addButton);
buttonPanel.add(editButton);
buttonPanel.add(deleteButton);
buttonPanel.add(browseButton);
buttonPanel.add(searchButton);
addButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
mdbw.goToAddPage();
}
});
editButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
mdbw.goToBrowse();
}
});
deleteButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
mdbw.goToBrowse();
}
});
browseButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
mdbw.goToBrowse();
}
});
searchButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
mdbw.goToSearch();
}
});
JFrame frame = new JFrame("Memory Files");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(700, 540);
frame.setLocation(250, 100);
frame.getContentPane().add(mdbw);
frame.getContentPane().add(buttonPanel);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
private CardLayout cardLayout = new CardLayout();
private JPanel cardShowingPanel = new JPanel(cardLayout);
public MyDatabaseWindow() {
Window1 win1 = new Window1();
cardShowingPanel.add(win1, FRONT_PAGE);
Window2 win2 = new Window2();
cardShowingPanel.add(win2, BROWSE_MEMORIES);
Window3 win3 = new Window3();
cardShowingPanel.add(win3, ADD_EDIT);
Window4 win4 = new Window4();
cardShowingPanel.add(win4, VIEW_MEMORY);
setLayout(new BorderLayout());
add(cardShowingPanel, BorderLayout.NORTH);
}
public void goToAddPage() {
cardLayout.first(cardShowingPanel);
}
public void goToBrowse() {
cardLayout.first(cardShowingPanel);
cardLayout.next(cardShowingPanel);
}
public void goToSearch() {
cardLayout.last(cardShowingPanel);
}
public void showCard(String key) {
cardLayout.show(cardShowingPanel, key);
}
}
class Window1 extends JPanel {
public Window1() {
init();
}
private void init() { //dummy details
JLabel title = new JLabel("Memory Files");
title.setBounds(0, 0, 500, 500);
add(title);
}
}
class Window2 extends JPanel {
public Window2() {
init();
}
private void init() { //dummy details
JLabel title = new JLabel("Memory Files");
title.setBounds(0, 0, 500, 500);
add(title);
}
}
class Window3 extends JPanel {
public Window3() {
init();
}
private void init() {//dummy details
JLabel title = new JLabel("Memory Files");
title.setBounds(0, 0, 500, 500);
add(title);
}
}
class Window4 extends JPanel {
public Window4() {
init();
}
private void init() {//dummy details
JLabel title = new JLabel("Memory Files");
title.setBounds(0, 0, 500, 500);
add(title);
}
}

The main problem is the use of null-layouts and these lines of code:
frame.getContentPane().add(mdbw);
frame.getContentPane().add(buttonPanel);
First you add the panel using the CardLayout to BorderLayout.CENTER, then you "overlay" it with your buttonPanel, which is using null-layout.
I would go with a simple FlowLayout (the default layout-manager for a JPanel) for the buttonPanel and add it to the BorderLayout.SOUTH of the contentPane. I would also strongly recommend reading this tutorial.
So remove the following lines of code:
buttonPanel.setLayout(null);
...
addButton.setBounds(100, 400, 100, 100);
editButton.setBounds(200, 400, 100, 100);
deleteButton.setBounds(300, 400, 100, 100);
browseButton.setBounds(400, 400, 100, 100);
searchButton.setBounds(500, 400, 100, 100);
and change frame.getContentPane().add(buttonPanel); to frame.getContentPane().add(buttonPanel, BorderLayout.SOUTH);.
Also forget about the null-layout / setBounds() in your Window-classes.
(Note that you still won't see the text change if you press a button because you always add a JLabel with the same text ("Memory Files") to your Windows.)

Focus navigation in keyBinding

In my form, when i press ENTER button in my keyboard, the okAction() method should be invoke (and invoke perfectly).
My problem is in focus state, When i fill the text fields and then press the ENTER button, the okAction() didn't invoked, because the focus is on the second text field (not on the panel).
How fix this problem?
public class T3 extends JFrame implements ActionListener {
JButton cancelBtn, okBtn;
JLabel fNameLbl, lNameLbl, tempBtn;
JTextField fNameTf, lNameTf;
public T3() {
add(createForm(), BorderLayout.NORTH);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(400, 500);
setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new T3();
}
});
}
public JPanel createForm() {
JPanel panel = new JPanel();
panel.getInputMap().put(KeyStroke.getKeyStroke("ENTER"), "Button");
panel.getActionMap().put("Button", new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
okAction();
}
});
okBtn = new JButton("Ok");
okBtn.addActionListener(this);
cancelBtn = new JButton("Cancel");
tempBtn = new JLabel();
fNameLbl = new JLabel("First Name");
lNameLbl = new JLabel("Last Name");
fNameTf = new JTextField(10);
fNameTf.setName("FnTF");
lNameTf = new JTextField(10);
lNameTf.setName("LnTF");
panel.add(fNameLbl);
panel.add(fNameTf);
panel.add(lNameLbl);
panel.add(lNameTf);
panel.add(okBtn);
panel.add(cancelBtn);
panel.add(tempBtn);
panel.setLayout(new SpringLayout());
SpringUtilities.makeCompactGrid(panel, 3, 2, 50, 10, 80, 60);
return panel;
}
private void okAction() {
if (fNameTf.getText().trim().length() != 0 && lNameTf.getText().trim().length() != 0) {
System.out.println("Data saved");
} else System.out.println("invalid data");
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == okBtn) {
okAction();
}
}
}

Declare a default button for your GUI's JRootPane:
public T3() {
//!! ..... etc...
setVisible(true);
getRootPane().setDefaultButton(okBtn);
}
In fact with a default button set, I don't see that you need to use key bindings.

Java Key Event won't execute once I press a button

Hi hope someone can tell me what I am doing wrong with my Key Event.
I am using a Card Layout to navigate through two of my JPanels atm. To do so I use Action Events as well as Key Events. The action events will toggle between JPanels when a button is pressed while the key events will hide away the buttons when a key is pressed. All good with the key events, it does what I want (call a method on one of the panels to set the bounds of the buttons placed inside it eq: button.setBounds(-1, -1, 150, 40); but when I press any of the buttons the key event wont respond despite not having any event on the buttons that I press. Below is my code, for simplicity I removed the non relevant parts of the panels like what they are meant to do.
Thanks in advance and please let me know if I need to provide more clues or to edit the code more, I will try my best to make the code clearer.
public class PanelContainer extends JPanel implements ActionListener, KeyListener{
GamePanel game = new GamePanel();
MainMenuPanel mainMenu = new MainMenuPanel();
CardLayout cards = new CardLayout();
public PanelContainer(){
setLayout(cards);
this.setFocusable(true);
this.addKeyListener(this);
mainMenu.newGameButton.addActionListener(this);
add(mainMenu, "Card1");
add(game, "Card2");
}
#Override
public void actionPerformed(ActionEvent aevt){
cards.show(this, "Card2");
game.action();
}
#Override
public void keyTyped(KeyEvent kevt){
}
#Override
public void keyPressed(KeyEvent kevt){
}
#Override
public void keyReleased(KeyEvent kevt){
if(kevt.getKeyCode() == KeyEvent.VK_ESCAPE || kevt.getKeyChar() == 'O' || kevt.getKeyChar() == 'o'){
game.shw(); //shw() is a method inside GamePanel that sets the bounds of the buttons
}
else if (kevt.getKeyChar() == 'h' || kevt.getKeyChar() == 'H'){game.hid();}
}
}
public class MainMenuPanel extends JPanel
{
private URL workingDir = this.getClass().getResource("imgresources/brick_wall.png") ;
private ImageIcon icon = new ImageIcon(workingDir) ;
private Image img = icon.getImage();
//create and initiate buttons;
JButton newGameButton = new JButton("New Game");
JButton highScoreButton = new JButton("High Scores");
JButton controlsButton = new JButton("Controls");
Point[] points = new Point[1000];
public MainMenuPanel(){
add(newGameButton);
add(highScoreButton);
add(controlsButton);
setPoints();
}
public void setButtonsBounds(){
newGameButton.setBounds(450, 200, 200, 40);
highScoreButton.setBounds(450, 250, 200, 40);
controlsButton.setBounds(450, 300, 200, 40);
}
#Override
public void paintComponent(Graphics g){
try{
super.paintComponent(g);
Graphics2D d2 = (Graphics2D) g;
d2.setColor(new Color(0, 0, 0));
d2.fillRect(0, 0, this.getWidth(), this.getHeight());
setButtonsBounds();
for(int i=0; i<275; i++){
d2.drawImage(img, points[i].x +200, points[i].y, this);
}
}catch(Exception e){}
}
}
public class GamePanel extends JPanel implements Runnable{
JButton button = new JButton("Main Menu");
JButton button2 = new JButton("Exit Game");
void shw(){
add(button);
add(button2);
button.setBounds(400, 200, 150, 20);
button2.setBounds(400, 240, 150, 20);
}
void hid(){
button.setBounds(1, 1, 150, 20);
button2.setBounds(1, 40, 150, 20);
}
}

It's a focus issue. Use Key Bindings instead of a KeyListener so you don't have to worry about this issue (and for other benefits as well -- check the Key Bindings tutorial for details).
Here's my SSCCE that demonstrates what I'm talking about. Note that both KeyListener and key bindings work until you press a button, and then only bindings work:
import java.awt.event.*;
import javax.swing.*;
public class KeyBindingsEg {
private static void createAndShowGui() {
PanelContainer mainPanel = new PanelContainer();
JFrame frame = new JFrame("KeyBindingsEg");
frame.setDefaultCloseOperation(JFrame.EXIT_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();
}
});
}
}
#SuppressWarnings("serial")
class PanelContainer extends JPanel {
public PanelContainer() {
this.setFocusable(true);
this.addKeyListener(new MyKeyListener());
JButton newGameButton = new JButton("New Game");
newGameButton.addActionListener(new MyActionListener());
add(newGameButton);
setKeyBindings();
}
private void setKeyBindings() {
Action hideAction = new BindingAction(BindingAction.HIDE);
Action showAction = new BindingAction(BindingAction.SHOW);
int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
InputMap inputMap = getInputMap(condition);
ActionMap actionMap = getActionMap();
actionMap.put(BindingAction.HIDE, hideAction);
inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_H, 0), BindingAction.HIDE);
inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_H, KeyEvent.SHIFT_DOWN_MASK),
BindingAction.HIDE);
int[] showKeys = { KeyEvent.VK_O, KeyEvent.VK_ESCAPE };
actionMap.put(BindingAction.SHOW, showAction);
for (int key : showKeys) {
inputMap.put(KeyStroke.getKeyStroke(key, 0), BindingAction.SHOW);
inputMap.put(KeyStroke.getKeyStroke(key, KeyEvent.SHIFT_DOWN_MASK),
BindingAction.SHOW);
}
}
private class MyActionListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent aevt) {
System.out.println("button pressed");
}
}
private class MyKeyListener extends KeyAdapter {
public void keyReleased(KeyEvent kevt) {
if (kevt.getKeyCode() == KeyEvent.VK_ESCAPE
|| kevt.getKeyChar() == 'O' || kevt.getKeyChar() == 'o') {
System.out.println("KeyListener: show");
} else if (kevt.getKeyChar() == 'h' || kevt.getKeyChar() == 'H') {
System.out.println("KeyListener: hide");
}
}
}
private class BindingAction extends AbstractAction {
public static final String HIDE = "Hide";
public static final String SHOW = "Show";
public BindingAction(String text) {
super(text);
putValue(ACTION_COMMAND_KEY, text);
}
#Override
public void actionPerformed(ActionEvent evt) {
String actionCommand = evt.getActionCommand();
if (actionCommand.equals(HIDE)) {
System.out.println("key bindings: hide");
} else if (actionCommand.equals(SHOW)) {
System.out.println("key bindings: show");
}
}
}
}

Java : Swing : Hide frame after button pressed

I have a button in a java frame that when pressed it reads a value from a text field and uses that string as a port name attempting to connect to a serial device.
If this connection is successful the method returns true if not it returns false. If it returns true I want the frame to disappear. A series of other frames specifed in other classes will then appear with options to control the serial device.
My problem is: the button is connected to an action listener, when pressed this method is invoked. If I try to use the frame.setVisible(true); method java throws a abstract button error because I'm effectively telling it to disappear the frame containing the button before the button press method has exited. Removing the frame.setVisible(true); allow the program to run correctly however I am left with a lingering connection frame that is no longer any use.
How to I get the frame to disappear upon pressing a the button?
package newimplementation1;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/**
*
* #author Zac
*/
public class ConnectionFrame extends JPanel implements ActionListener {
private JTextField textField;
private JFrame frame;
private JButton connectButton;
private final static String newline = "\n";
public ConnectionFrame(){
super(new GridBagLayout());
textField = new JTextField(14);
textField.addActionListener(this);
textField.setText("/dev/ttyUSB0");
connectButton = new JButton("Connect");
//Add Components to this panel.
GridBagConstraints c = new GridBagConstraints();
c.gridwidth = GridBagConstraints.REMAINDER;
c.fill = GridBagConstraints.HORIZONTAL;
add(textField, c);
c.fill = GridBagConstraints.BOTH;
c.weightx = 1.0;
c.weighty = 1.0;
add(connectButton, c);
connectButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{
boolean success = Main.mySerialTest.initialize(textField.getText());
if (success == false) {System.out.println("Could not connect"); return;}
frame.setVisible(false); // THIS DOES NOT WORK!!
JTextInputArea myInputArea = new JTextInputArea();
myInputArea.createAndShowGUI();
System.out.println("Connected");
}
});
}
public void actionPerformed(ActionEvent evt) {
// Unimplemented required for JPanel
}
public void createAndShowGUI() {
//Create and set up the window.
frame = new JFrame("Serial Port Query");
frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
//Add contents to the window.
frame.add(new ConnectionFrame());
frame.setLocation(300, 0);
//Display the window.
frame.pack();
frame.setVisible(true);
frame.addComponentListener(new ComponentAdapter() {
#Override
public void componentHidden(ComponentEvent e) {
System.out.println("Exiting Gracefully");
Main.mySerialTest.close();
((JFrame)(e.getComponent())).dispose();
System.exit(0);
}
});
}
}

Running your snippet (after removing/tweaking around the custom classes), throws an NPE. Reason is that the frame you'r accessing is null. And that's because it's never set. Better not rely on any field, let the button find its toplevel ancestor and hide that, like in
public void actionPerformed(final ActionEvent e) {
boolean success = true;
if (success == false) {
System.out.println("Could not connect");
return;
}
Window frame = SwingUtilities.windowForComponent((Component) e
.getSource());
frame.setVisible(false); //no problem :-)
}

Your problem is with this line:
frame.add(new ConnectionFrame());
You're creating a new ConnectionFrame object, and so the frame that your button tries to close on is not the same as the one being displayed, and this is the source of your problem.
If you change it to,
//!! frame.add(new ConnectionFrame());
frame.add(this);
so that the two JFrames are one and the same, things may work more smoothly.
But having said that, your whole design smells bad and I'd rethink it in a more OOP and less static fashion. Also, use dialogs where dialogs are needed, not frames, and rather than dialogs consider swapping views (JPanels) via CardLayout as a better option still.
Myself, I'd create a "dumb" GUI for this, one that creates a JPanel (here in my example it extends a JPanel for simplicity, but I'd avoid extending if not necessary), and I'd let whoever is calling this code decide what to do with the information via some control. For e.g.,
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
#SuppressWarnings("serial")
public class ConnectionPanel extends JPanel {
private JTextField textField;
private JButton connectButton;
private ConnectionPanelControl control;
public ConnectionPanel(final ConnectionPanelControl control) {
super(new GridBagLayout());
this.control = control;
ActionListener listener = new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (control != null) {
control.connectButtonAction();
}
}
};
textField = new JTextField(14);
textField.addActionListener(listener);
textField.setText("/dev/ttyUSB0");
connectButton = new JButton("Connect");
GridBagConstraints c = new GridBagConstraints();
c.gridwidth = GridBagConstraints.REMAINDER;
c.fill = GridBagConstraints.HORIZONTAL;
add(textField, c);
c.fill = GridBagConstraints.BOTH;
c.weightx = 1.0;
c.weighty = 1.0;
add(connectButton, c);
connectButton.addActionListener(listener);
}
public String getFieldText() {
return textField.getText();
}
}
Again, something outside of the simple GUI would make decisions on what to do with the text that the textfield contains and what to do with the GUI that is displaying this JPanel:
public interface ConnectionPanelControl {
void connectButtonAction();
}
Also, you will likely do any connecting in a background thread so as to not freeze your GUI, probably a SwingWorker. Perhaps something like this:
import java.awt.event.ActionEvent;
import java.util.concurrent.ExecutionException;
import javax.swing.*;
#SuppressWarnings("serial")
public class MyMain extends JPanel {
public MyMain() {
add(new JButton(new ConnectionAction("Connect", this)));
}
private static void createAndShowGui() {
JFrame frame = new JFrame("My Main");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new MyMain());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
#SuppressWarnings("serial")
class ConnectionAction extends AbstractAction {
private MyMain myMain;
private ConnectionPanel cPanel = null;
private JDialog dialog = null;
public ConnectionAction(String title, MyMain myMain) {
super(title);
this.myMain = myMain;
}
#Override
public void actionPerformed(ActionEvent e) {
if (dialog == null) {
dialog = new JDialog(SwingUtilities.getWindowAncestor(myMain));
dialog.setTitle("Connect");
dialog.setModal(true);
cPanel = new ConnectionPanel(new ConnectionPanelControl() {
#Override
public void connectButtonAction() {
final String connectStr = cPanel.getFieldText();
new MySwingWorker(connectStr).execute();
}
});
dialog.getContentPane().add(cPanel);
dialog.pack();
dialog.setLocationRelativeTo(null);
}
dialog.setVisible(true);
}
private class MySwingWorker extends SwingWorker<Boolean, Void> {
private String connectStr = "";
public MySwingWorker(String connectStr) {
this.connectStr = connectStr;
}
#Override
protected Boolean doInBackground() throws Exception {
// TODO: make connection and then return a result
// right now making true if any text in the field
if (!connectStr.isEmpty()) {
return true;
}
return false;
}
#Override
protected void done() {
try {
boolean result = get();
if (result) {
System.out.println("connection successful");
dialog.dispose();
} else {
System.out.println("connection not successful");
}
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
}
}

Your code would be much more readable if you named JFrame instances xxxFrame, and JPanel instances xxxPanel. Naming JPanel instances xxxFrame makes things very confusing.
It would also help if you pasted the stack trace of the exception.
I suspect the problem comes from the fact that frame is null. This is due to the fact that the frame field is only initialized in the createAndShowGUI method, but this method doesn't display the current connection panel, but a new one, which thus have a null frame field:
ConnectionFrame firstPanel = new ConnectionFrame();
// The firstPanel's frame field is null
firstPanel.createAndShowGUI();
// the firstPanel's frame field is now not null, but
// the above call opens a JFrame containing another, new ConnectionFrame,
// which has a null frame field
The code of createAndShowGUI should contain
frame.add(this);
rather than
frame.add(new ConnectionFrame());

for Swing GUI is better create only once JFrame and another Top-Level Containers would be JDialog or JWindow(un-decorated by default),
simple example here
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class SuperConstructor extends JFrame {
private static final long serialVersionUID = 1L;
public SuperConstructor() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setPreferredSize(new Dimension(300, 300));
setTitle("Super constructor");
Container cp = getContentPane();
JButton b = new JButton("Show dialog");
b.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent evt) {
FirstDialog firstDialog = new FirstDialog(SuperConstructor.this);
}
});
cp.add(b, BorderLayout.SOUTH);
JButton bClose = new JButton("Close");
bClose.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent evt) {
System.exit(0);
}
});
add(bClose, BorderLayout.NORTH);
pack();
setVisible(true);
}
public static void main(String args[]) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
SuperConstructor superConstructor = new SuperConstructor();
}
});
}
private class FirstDialog extends JDialog {
private static final long serialVersionUID = 1L;
FirstDialog(final Frame parent) {
super(parent, "FirstDialog");
setPreferredSize(new Dimension(200, 200));
setLocationRelativeTo(parent);
setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
setModalityType(Dialog.ModalityType.DOCUMENT_MODAL);
JButton bNext = new JButton("Show next dialog");
bNext.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent evt) {
SecondDialog secondDialog = new SecondDialog(parent, false);
}
});
add(bNext, BorderLayout.NORTH);
JButton bClose = new JButton("Close");
bClose.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent evt) {
setVisible(false);
}
});
add(bClose, BorderLayout.SOUTH);
pack();
setVisible(true);
}
}
private int i;
private class SecondDialog extends JDialog {
private static final long serialVersionUID = 1L;
SecondDialog(final Frame parent, boolean modal) {
//super(parent); // Makes this dialog unfocusable as long as FirstDialog is visible
setPreferredSize(new Dimension(200, 200));
setLocation(300, 50);
setModal(modal);
setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
setTitle("SecondDialog " + (i++));
JButton bClose = new JButton("Close");
bClose.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent evt) {
setVisible(false);
}
});
add(bClose, BorderLayout.SOUTH);
pack();
setVisible(true);
}
}
}
better would be re-use Top-Level Containers, as create lots of Top-Level Containers on Runtime (possible memory lack)