Develop Reference

Add graphics on a Jpanel Object with Thread

I want to add graphics in this program. The graphics will be drawn on "drawPanel" object. I have to use thread here.
No idea for drawing in a Jpanel object with thread. What will be the good efficient way to draw graphics on that Jpanel Object?
How thread and paintComponent() going to interact.Thanks.
Code:
public class LinearSearch extends JPanel{
private final Font LABEL_FONT = new Font("courier", Font.BOLD, 30);
private JPanel mainPanel;
private JPanel centerPanel;
private JPanel inputPanel;
private JPanel drawPanel;
private JLabel lblTitle;
private Button btnBack;
public LinearSearch(JPanel mainPanel) {
this.mainPanel = mainPanel;
setBackground(Color.WHITE);
initialize_All();
}
private void initialize_All() {
lblTitle = new JLabel("\"Linear Search\"", SwingConstants.CENTER);
lblTitle.setFont(LABEL_FONT);
///Center Panel
centerPanel = new JPanel();
centerPanel.setLayout(new BorderLayout());
///Input Panel
inputPanel = new JPanel();
inputPanel.setLayout(new BoxLayout(inputPanel, BoxLayout.X_AXIS));
///Draw Panel
drawPanel = new JPanel();
drawPanel.setLayout(new FlowLayout());
/// I want to add graphics on this drawPanel Jpanel
btnBack = new Button("Back");
btnBack.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
setVisible(false);
removeAll();
mainPanel.add(new CatagoriesMenu(mainPanel));
}
});
setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
setLayout(new BorderLayout(10, 10));
add(lblTitle, BorderLayout.PAGE_START);
add(centerPanel, BorderLayout.CENTER);
add(btnBack, BorderLayout.PAGE_END);
centerPanel.add(inputPanel, BorderLayout.PAGE_START);
centerPanel.add(drawPanel, BorderLayout.CENTER);
}
}

I must need to add graphics on "drawPanel" Jpanel Object.
Then you need to extend the JPanel and override the paintComponent(...) method to do your custom painting.
Read the section from the Swing tutorial on Custom Painting for more information and working examples to get you started.

Just need to add this class object from another class in add() method.
This will work (tested):
public class LinearSearchSimulation extends JPanel implements Runnable{
private final int DELAY = 50;
private JPanel mainPanel;
int x=0, y=0;
private Thread thread;
private boolean threadFlag = false;
public LinearSearchSimulation(JPanel mainPanel){
this.mainPanel = mainPanel;
setBackground(Color.WHITE);
}
public void start() {
if (threadFlag) {
return;
}
threadFlag = true;
thread = new Thread(this);
thread.start();
}
public void stop() {
if (!threadFlag) {
return;
}
threadFlag = false;
try {
thread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.fillOval(x,y, 55, 55);
g.dispose();
}
public void update() {
x += 1;
y += 1;
}
#Override
public void run() {
long beforeTime, timeDiff, sleep;
beforeTime = System.currentTimeMillis();
while (threadFlag) {
update();
repaint();
timeDiff = System.currentTimeMillis() - beforeTime;
sleep = DELAY - timeDiff;
if (sleep < 0)
sleep = 2;
try {
Thread.sleep(sleep);
} catch (InterruptedException e) {
System.out.println("interrupted");
}
beforeTime = System.currentTimeMillis();
}
}
}

JTabbedPane TabComponent default tab highlighting

I have a question regarding custom tab components in swing.
The following code will add 3 custom tab components:
public class TabbedExample extends JPanel {
public static void main(String... args) {
EventQueue.invokeLater(new Runnable() {
#Override public void run() {
createUI();
}
}
}
public static void createUI() {
try {
for(LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
if("Nimbus".equals(info.getName())) {
UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch(Exception e) {}
JFrame frame = new JFrame("Tab Test");
frame.setMinimumSize(new Dimension(256,200));
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.getContentPane().add(new TabbedExample());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public TabbedExample() {
super(new BorderLayout());
JTabbedPane pane = new JTabbedPane();
pane.addTab("tmp", new JTextField());
pane.addTab("tmp", new JTextField());
pane.addTab("tmp", new JTextField());
for(int i = 0; i < 3; i++) {
JPanel tabPanel = new JPanel();
tabPanel.setBackground(new Color(0,0,0,0));
tabPanel.setLayout(new BoxLayout(tabPanel, BoxLayout.X_AXIS));
JTextField textField = new JTextField("Tab " + i);
textField.setOpaque(false);
textField.setBackground(new Color(0,0,0,0));
textField.setBorder(new EmptyBorder(0,0,0,0));
tabPanel.add(label);
tabPanel.add(new JButton(Integer.toString(i)));
pane.setTabComponentAt(i, tabPanel);
}
add(pane, BorderLayout.CENTER);
}
}
the problem now is that the default tab behaviour stops working. normally, when you move your mouse over a tab, it automagically gets highlight by changing the background color. but as soon as the JTextField is hit, the tab most likely registers a mouseExited Event and stops the highlighting of the tab. so the tab will flicker when you move your mouse over the tab.
my question now is:
Is there a way (without implementing a new highlighting mechanism) to highlight the tab, where the custom tabComponent is located?

Here's my attempt:
Using a JLayer to dispatch the MouseMotionEvent from the tabs to the parent JTabbedPane:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.plaf.*;
public class TabbedExample2 extends JPanel {
public static void main(String... args) {
EventQueue.invokeLater(() -> {
createUI();
});
}
public static void createUI() {
try {
for (UIManager.LookAndFeelInfo laf: UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(laf.getName())) {
UIManager.setLookAndFeel(laf.getClassName());
}
}
} catch (Exception e) {
e.printStackTrace();
}
JFrame frame = new JFrame("Tab Test");
frame.setMinimumSize(new Dimension(256, 200));
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.getContentPane().add(new TabbedExample2());
frame.setSize(320, 240);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public TabbedExample2() {
super(new BorderLayout());
JTabbedPane pane = new JTabbedPane();
pane.addTab("tmp", new JTextField(16));
pane.addTab("tmp", new JTextField(16));
pane.addTab("tmp", new JTextField(16));
for (int i = 0; i < 3; i++) {
JPanel tabPanel = new JPanel();
tabPanel.setOpaque(false);
//tabPanel.setBackground(new Color(0,0,0,0));
tabPanel.setLayout(new BoxLayout(tabPanel, BoxLayout.X_AXIS));
JTextField textField = new JTextField("Tab " + i);
//textField.setBackground(new Color(0,0,0,0));
//textField.setBorder(new EmptyBorder(0,0,0,0));
//tabPanel.add(label); //???
tabPanel.add(textField);
tabPanel.add(new JButton(Integer.toString(i)));
pane.setTabComponentAt(
i, new JLayer<JPanel>(tabPanel, new DispatchEventLayerUI()));
}
add(pane);
}
}
class DispatchEventLayerUI extends LayerUI<JPanel> {
#Override
public void installUI(JComponent c) {
super.installUI(c);
if (c instanceof JLayer) {
((JLayer) c).setLayerEventMask(AWTEvent.MOUSE_MOTION_EVENT_MASK);
//TEST:
//((JLayer) c).setLayerEventMask(
// AWTEvent.MOUSE_EVENT_MASK | AWTEvent.MOUSE_MOTION_EVENT_MASK);
}
}
#Override
public void uninstallUI(JComponent c) {
if (c instanceof JLayer) {
((JLayer) c).setLayerEventMask(0);
}
super.uninstallUI(c);
}
// //TEST:
// #Override
// protected void processMouseEvent(MouseEvent e, JLayer<? extends JPanel> l) {
// dispatchEvent(e);
// }
#Override
protected void processMouseMotionEvent(MouseEvent e, JLayer<? extends JPanel> l) {
dispatchEvent(e);
}
private void dispatchEvent(MouseEvent e) {
Component src = e.getComponent();
Container tgt = SwingUtilities.getAncestorOfClass(JTabbedPane.class, src);
tgt.dispatchEvent(SwingUtilities.convertMouseEvent(src, e, tgt));
}
}

Why is Plot2DPanel not reacting to its MouseListener's click event?

I learned recently how to switch between Jpanels in CardLayout.
The code works fine but when I attempt to change one of jPanels to Plot2DPanel I get a strange behaviour at runtime. The Plot2DPanel isn't picking up its mouse click events. What have I done wrong? (I assume that is not a bug in jmathplot).
Here's the code:
public class Window {
private JFrame frame;
private JPanel cards;
private JPanel panelOne;
private Plot2DPanel panelTwo;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Window window = new Window();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public Window() {
initialize();
}
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 790, 483);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
cards = new JPanel();
cards.setLayout(new CardLayout());
panelOne = new JPanel();
panelOne.setBackground(Color.BLACK);
panelOne.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e){
java.awt.Toolkit.getDefaultToolkit().beep(); //debug beep
CardLayout cl = (CardLayout) cards.getLayout();
cl.next(cards);
}
});
panelTwo = new Plot2DPanel();
panelTwo.setBackground(Color.WHITE);
panelTwo.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e){
java.awt.Toolkit.getDefaultToolkit().beep(); //debug beep
CardLayout cl = (CardLayout) cards.getLayout();
cl.next(cards);
}
});
cards.add(panelOne, "panel1");
cards.add(panelTwo, "panel2");
frame.getContentPane().add(cards);
}
}

Closing and reopeing of frame happens with increasing frequency each a button is pressed a single time

I am using a self made toolbar to navigate through my application and the toolbar is present on all pages. Each time a new page is displayed I am closing the current frame and opening a new one, using the following code:
java.awt.Window win[] = java.awt.Window.getWindows();
for(int i=0;i<win.length;i++){
win[i].dispose();
}
I am doing it this way as the ActionListeners are declared in the toolbar class, whilst the frames for each page are declared at runtime and are not static.
This all works fine except for one particular case-the "cancel" button, where the first time the frame is accessed it will close once. The second time it will close and re open 2 times, the third 3 and so on. I have tracked this using the "counter" in the code.
I have minimised the code to recreate the same behaviour, as below:
Toolbar Class
public class Toolbar {
static JButton buttonCancel = new JButton("Cancel");
static int counter;
public static JPanel Toolbar(String panelname){
FlowLayout layout = new FlowLayout();
JPanel Toolbar = new JPanel(new BorderLayout());
Toolbar.setLayout(layout);
GridLayout GLayout = new GridLayout(2,1);
GLayout.setVgap(0);
JPanel container2 = new JPanel();
if(panelname.matches("Customers")){
container2.setLayout(GLayout);
JButton buttonAddCust = new JButton("Add Cust");
container2.add(buttonAddCust, BorderLayout.PAGE_START);
buttonAddCust.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
java.awt.Window win[] = java.awt.Window.getWindows();
for(int i=0;i<win.length;i++){
win[i].dispose();
}
Customers.AddCustomersGui();
}
});
}
JPanel container21 = new JPanel();
if(panelname.matches("Add Customers")){
container21.setLayout(GLayout);
container21.add(buttonCancel, BorderLayout.PAGE_START);
buttonCancel.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
counter ++;
java.awt.Window win[] = java.awt.Window.getWindows();
for(int i=0;i<win.length;i++){
win[i].dispose();
}
System.out.println("Coutner " + counter);
Customers.CustomersGui();
}
});
}
Toolbar.add(container2);
Toolbar.add(container21);
return Toolbar;
}
}
GUI class
public class Customers extends Toolbar{
public static void CustomersGui(){
final JFrame frame = new JFrame("Customers");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel customers = new JPanel();
customers.add(Toolbar.Toolbar(frame.getTitle()));
frame.setContentPane(customers);
frame.setSize(1200,500);
frame.setVisible(true);
}
public static void AddCustomersGui(){
final JFrame frame1 = new JFrame("Add Customers");
frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel Addcustomers = new JPanel();
Addcustomers.add(Toolbar.Toolbar(frame1.getTitle()));
frame1.setContentPane(Addcustomers);
frame1.setSize(1200,500);
frame1.setVisible(true);
}
}
main class
public static void main(String[] args) {
Customers.CustomersGui();
}

You are adding a new ActionListener to the buttonCancel, with each iteration of your code and this is the reason for your program's behavior.
Also, as per my comment, you state,
Each time a new page is displayed I am closing the current frame and opening a new one.
A better design is probably not to swap windows which can be annoying, but rather to swap JPanel views using a CardLayout. Please read The Use of Multiple JFrames, Good/Bad Practice?.
For example, add this line of code to your program:
if (panelname.matches("Add Customers")) {
container21.setLayout(GLayout);
container21.add(buttonCancel, BorderLayout.PAGE_START);
buttonCancel.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
counter++;
java.awt.Window win[] = java.awt.Window.getWindows();
for (int i = 0; i < win.length; i++) {
win[i].dispose();
}
System.out.println("Coutner " + counter);
Customers.CustomersGui();
}
});
// ***** add this here **********
System.out.println("buttonCancel ActionListener count: "
+ buttonCancel.getListeners(ActionListener.class).length);
}
and you'll see that the ActionListeners get added multiple times to this button.
An example of swapping views:
import java.awt.*;
import java.awt.event.ActionEvent;
import javax.swing.*;
#SuppressWarnings("serial")
public class SwapPanels extends JPanel {
public static final String CUSTOMER = "customer";
public static final String ADD_CUSTOMER = "Add Customer";
protected static final int PREF_W = 800;
protected static final int PREF_H = 600;
public static final String CANCEL = "Cancel";
private CardLayout cardLayout = new CardLayout();
public SwapPanels() {
setLayout(cardLayout);
add(createCustomerPanel(CUSTOMER), CUSTOMER);
add(createAddCustomerPanel(ADD_CUSTOMER), ADD_CUSTOMER);
}
public void showCard(String key) {
cardLayout.show(this, key);
}
public JPanel createAddCustomerPanel(String name) {
JPanel addCustPanel = new JPanel() {
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
};
addCustPanel.setName(name);
addCustPanel.setBorder(BorderFactory.createTitledBorder(name));
addCustPanel.add(new JButton(new AbstractAction(CANCEL) {
{
int mnemonic = (int)getValue(NAME).toString().charAt(0);
putValue(MNEMONIC_KEY, mnemonic);
}
#Override
public void actionPerformed(ActionEvent e) {
if (CANCEL.equals(e.getActionCommand())) {
SwapPanels.this.showCard(CUSTOMER);
}
}
}));
return addCustPanel;
}
private JPanel createCustomerPanel(String name) {
JPanel custPanel = new JPanel() {
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
};
custPanel.setName(name);
custPanel.setBorder(BorderFactory.createTitledBorder(name));
custPanel.add(new JButton(new AbstractAction(ADD_CUSTOMER) {
{
int mnemonic = (int)getValue(NAME).toString().charAt(0);
putValue(MNEMONIC_KEY, mnemonic);
}
#Override
public void actionPerformed(ActionEvent e) {
if (ADD_CUSTOMER.equals(e.getActionCommand())) {
SwapPanels.this.showCard(ADD_CUSTOMER);
}
}
}));
return custPanel;
}
private static void createAndShowGui() {
JFrame frame = new JFrame("SwapPanels");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new SwapPanels());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}

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)