Develop Reference

Java: The escape key is always pressed after dispatchEvent() for WINDOW_CLOSING on a JFrame

I have a simple JFrame that asks a user for a confirmation to exit when they click X to close the window, this works fine. I also wanted the user to be presented with the same option if they also pressed the escape key (ESC), unfortunately it seems to be trapped in a state where the escape key seems to be constantly pressed when it is not. Where is the mistake and why?
public class Zz extends javax.swing.JFrame implements Events {
boolean exitAttempt = false;
java.awt.event.WindowEvent closeEvent;
//public Zz() {}
public static void main(java.lang.String[] args) {
Zz zz = new Zz();
zz.dostuff();
}
public void dostuff() {
setSize(800, 600);
setLocationRelativeTo(null);
setResizable(false);
setDefaultCloseOperation(javax.swing.JFrame.DO_NOTHING_ON_CLOSE);
addWindowListener(new java.awt.event.WindowAdapter() {
public void windowClosing(java.awt.event.WindowEvent we) {
exitAttempt = true;
}
});
closeEvent = new java.awt.event.WindowEvent(
this, java.awt.event.WindowEvent.WINDOW_CLOSING);
setVisible(true);
java.awt.Canvas canvas = new java.awt.Canvas();
canvas.setPreferredSize(new java.awt.Dimension(800, 600));
add(canvas);
Keys keys = new Keys();
addKeyListener(keys);
pack();
while (true) {
events(keys);
if (exitAttempt) {
if (javax.swing.JOptionPane.YES_OPTION ==
showConfirmDialog("Do you want to Exit ?",
"Confirmation:", javax.swing.JOptionPane.YES_NO_OPTION,
javax.swing.JOptionPane.QUESTION_MESSAGE, null)) {
exit();
break; //while loop
}
exitAttempt = false;
}
}
dispose();
}
public void triggerCloseEvent() {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
dispatchEvent(closeEvent);
}
});
}
public int showConfirmDialog(java.lang.Object message,
java.lang.String title, int optionType, int messageType,
javax.swing.Icon icon) {
return javax.swing.JOptionPane.showConfirmDialog(
this, message, title, optionType, messageType, icon);
}
public boolean exit() {
setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE);
return true;
}
public void events(Keys keys) {
System.out.println((keys.getPressed())[java.awt.event.KeyEvent.VK_ESCAPE]);
if ((keys.getPressed())[java.awt.event.KeyEvent.VK_ESCAPE]) {
triggerCloseEvent();
}
}
}
interface Events {
public void events(Keys keys);
}
class Keys implements java.awt.event.KeyListener {
private final boolean[] pressed;
public Keys() {
pressed = new boolean[256];
}
public void keyTyped(java.awt.event.KeyEvent event) {}
public void keyPressed(java.awt.event.KeyEvent event) {
pressed[event.getKeyCode()] = true;
}
public void keyReleased(java.awt.event.KeyEvent event) {
pressed[event.getKeyCode()] = false;
}
public boolean[] getPressed() {
return pressed;
}
}

I have a simple JFrame that asks a user for a confirmation to exit when they click X to close the window, this works fine
Your design is incorrect.
You should NOT have a while (true) loop.
GUI's are event driven. You create the frame and make it visible. That is the end of the code in your main() method or constructor. The GUI will then sit there forever doing nothing.
However, eventually, the user will then generate events that the GUI responds to.
This means that the code to display the JOptionPane should be moved to the windowClosing() method of your WindowListener.
See: Closing an Application for some basics and helpful classes to use.
I also wanted the user to be presented with the same option if they also pressed the escape key
Don't use a KeyListener.
Swing was designed to be used with Key Bindings.
You can use the ExitAction contained in the Closing an Application link when creating your key bindings:
KeyStroke escapeKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_ESCAPE, 0, false);
InputMap im = frame.getRootPane().getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT);
im.put(escapeKeyStroke, "escape");
frame.getRootPane().getActionMap().put("escape", new ExitAction());
Read the Swing tutorial. There are section on :
How to Uuse Key Bindings
How to Use Actions
to help explain how the above suggestions work.
The tutorial examples will also show you how to better structure your code and note that the never use a while (true) loop.

Implementing a JMenu with actionPerformed using TextAction

I have a Java Swing interface with multiple JTextArea's and I am implementing an "Edit" menu with various different functions like "Find", "Copy", "Paste", etc. When I click on the JMenuItem I need to know which JTextArea had the focus which is achievable through a TextAction (I haven't gone down the route of a FocusListener and keeping track of what last had the focus):
JMenuItem miFind = new JMenuItem(new EditHandler("Find"));
class EditHandler extends TextAction {
private String s = null;
public EditHandler(String vs) {
super(vs);
s = vs;
}
#Override
public void actionPerformed(ActionEvent e) {
JTextComponent c = getFocusedComponent();
if (s.equals("Find")) {
showFindDialog(c);
}
}
}
This works well and good but I want to be able to disable the "Find" JMenuItem under certain contexts (i.e. if the specific JTextArea is disabled or is empty. I can implement an ActionListener on a JMenu but I can't use getFocusedComponent() to identify what JTextArea has the focus.
According to the Java docs the JMenu constructor takes an Action (like a JMenuItem) and I have tried the following:
mEdit = new JMenu(new EditHandler("Edit"));
However, although the constructor fires, the actionPerformed() event isn't firing within my EditHandler for the JMenu. If I can get it to fire then I was planning to either enable or disable my "Find" JMenuItem.

The best way for you is using of actions map of the text component to place the corresponding action. In this case you can disable it for some text components.
#Override
public void actionPerformed(ActionEvent e) {
JTextComponent c = getFocusedComponent();
if (s.equals("Find")) {
Action a = c.getActionMap().get("Find");
if (a.isEnabled()) {
// generate new event to modify the source (menu item -> text component)
ActionEvent ae = new ActionEvent(c, e.getID(), e.getCommand());
a.actionPerformed(ae);
}
}
}
For each your text component you must provide an action and register it using the action map of the component.
public class UniversalFindAction extends AbstractAction {
public void actionPerformed(ActionEvent ae) {
JTextComponent c = (JTextComponent) ae.getSource();
showFindDialog(c);
}
}
// registering of action
JTextComponent comp = new JTextArea();
comp.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_F, InputEvent.CTRL_DOWN_MASK), "Find");
comp.getActionMap().put("Find", new UniversalFindAction());

Thanks to #sergiy-medvynskyy I have implemented a Global Focus Listener to keep track of the last JTextArea to be focused:
KeyboardFocusManager.getCurrentKeyboardFocusManager().addPropertyChangeListener("permanentFocusOwner", new PropertyChangeListener() {
#Override
public void propertyChange(final PropertyChangeEvent e) {
if (e.getNewValue() instanceof JTextArea) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
tFocused = (JTextArea)e.getNewValue();
}
});
}
}
});
I then check the tFocused object using a MenuListener on my JMenu to verify what JTextArea currently has the focus. I can then call setEnabled() on my respective JMenuItem's depending on the context.

Pass fields with enter key?

I'm looking for a way to pass fields with enter key in VerticalLayout or others. In vaadin book there an example with Shortcut and Handler listeners but I don't know how to implement that.
I'm trying this.
public class MyWindow extends Window implements Handler{
private Action action_enter; //pass fields with enter
private Action action_esc;
private TextField name, lastName;
public MyWindow(){
super("this window is opened");
VerticalLayout vLayout = new VerticalLayout();
setContent(vLayout);
center();
setModal(true);
setClosable(false);
setDraggable(false);
setResizable(false);
//actions
action_enter = new ShortcutAction("Enter key", ShortcutAction.KeyCode.ENTER, null);
action_esc = new ShortcutAction("Esc key", ShortcutAction.KeyCode.ESCAPE, null);
addActionHandler(this);
//fields
name = new TextField("Name");
lastName = new TextField("Last name");
name.focus();
vLayout.addComponent(name);
vLayout.addComponent(lastName);
}
#Override
public Action[] getActions(Object target, Object sender) {
return new Action[] { action_enter, action_esc };
}
#Override
public void handleAction(Action action, Object sender, Object target) {
/** close window with esc key */
if(action == action_esc){
close();
}
/** pass fields with enter key */
if(action == action_enter){
//here pass fields with enter key
}
}
}
any idea ?

try this way with ShortcutListener:
ShortcutListener skEnterListener = new ShortcutListener("Enter", ShortcutAction.KeyCode.ENTER, null){
#Override
public void handleAction(Object sender, Object target) {
if (target instanceof VerticalLayout) { // VerticalLayout or other
// sending fileds here
}
}
};
addShortcutListener(skEnterListener);
change focus of TextField using Enter instead Tab:
final TextField tf1 = new TextField("tf1");
tf1.setId("tf1");
final TextField tf2 = new TextField("tf2");
tf2.setId("tf2");
ShortcutListener skEnterListener = new ShortcutListener("Enter", ShortcutAction.KeyCode.ENTER, null){
#Override
public void handleAction(Object sender, Object target) {
if (target instanceof TextField) {
TextField field = (TextField) target;
if ("tf1".equals(field.getId())) {
tf2.focus();
}
if ("tf2".equals(field.getId())) {
tf1.focus();
}
}
}
};
addShortcutListener(skEnterListener);

There is no interface which does provide an accessor that would allow you finding out the currently focused component. Focus information can be acquired for some (but not all) field components through the com.vaadin.event.FieldEvents.FocusListener and com.vaadin.event.FieldEvents.BlurListener interfaces.
You could add for all possible fields a FocusListener and remember every time it's invoked, the current field in a variable. (Problem: not all fields provide a FocusListener.) Then when ENTER is pressed focus the next component according to the current focused field (remember the variable) that has to be focused (with the help of a simple List, LinkedList, Map, switch-case and so forth). To make it even better add a BlurListener as well to know when not to focus the next field.
Hope that helps.

JPanel Action Listener

I have a JPanel with a bunch of different check boxes and text fields, I have a button that's disabled, and needs to be enabled when specific configurations are setup.
What I need is a listener on the the whole JPanel looking for events, whenever anything changes.
I believe I need an action listener but I can't find anything to bridge the action Listener with the JPanel
JPanel Window = new JPanel();
Window.addActionListener(new ActionListener(){
//Check if configurations is good
}
I figure I can copy and paste my code a bunch of times into every listener in the panel, but that seems like bad coding practice to me.

First off as #Sage mention in his comment a JPanel is rather a container than a component which do action. So you can't attach an ActionListener to a JPanel.
I figure I can copy and paste my code a bunch of times into every
listener in the panel, but that seems like bad coding practice to me.
You're totally right about that, it's not a good practice at all (see DRY principle). Instead of that you can define just a single ActionListener and attach it to your JCheckBoxes like this:
final JCheckBox check1 = new JCheckBox("Check1");
final JCheckBox check2 = new JCheckBox("Check2");
final JCheckBox check3 = new JCheckBox("Check3");
final JButton buttonToBeEnabled = new JButton("Submit");
buttonToBeEnabled.setEnabled(false);
ActionListener actionListener = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
boolean enable = check1.isSelected() && check3.isSelected();
buttonToBeEnabled.setEnabled(enable);
}
};
check1.addActionListener(actionListener);
check2.addActionListener(actionListener);
check3.addActionListener(actionListener);
This means: if check1 and check3 are both selected, then the button must be enabled, otherwise must be disabled. Of course only you know what combination of check boxes should be selected in order to set the button enabled.
Take a look to How to Use Buttons, Check Boxes, and Radio Buttons tutorial.

A suggestion could be to derive a class from each of the components you're using and add an ActionListener that bubbles up the Container tree and looks for the first Container that implements a custom interface like this:
public interface MyCommandProcessor {
void execute(String actionCommand);
}
public class MyButton extends JButton {
public MyButton(string actionCommand) {
setActionCommand(actionCommand);
addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent ae) {
Container traverser = MyButton.this;
while (traverser != null && !(traverser instanceof MyCommandProcessor))
traverser = traverser.getParent();
if (traverser != null)
((CommandListener)traverser).execute(ae.getActionCommand());
}
});
}
}
public class MyApp extends JFrame implements MyCommandListener {
public MyApp() {
JPanel panel = new Panel();
panel.add(new MyButton("MyButton got pressed"));
}
public void execute(String actionCommand) {
System.out.println(actionCommand);
}
}

You need to create custom component listener. Look here:
Create a custom event in Java
Creating Custom Listeners In Java
http://www.javaworld.com/article/2077333/core-java/mr-happy-object-teaches-custom-events.html
I do it throw the standard ActionListener
Example
public class MyPanel extends JPanel {
private final JComboBox<String> combo1;
private final JButton btn2;
.......
//catch the actions of inside components
btn2.addActionListener(new MyPanelComponentsActionListener());
........
//assign actionlistener to panel class
public void addActionListener(ActionListener l) {
listenerList.add(ActionListener.class, l);
}
public void removeActionListener(ActionListener l) {
listenerList.remove(ActionListener.class, l);
}
//handle registered listeners from components used MyPanel class
protected void fireActionPerformed(ActionEvent event) {
// Guaranteed to return a non-null array
Object[] listeners = listenerList.getListenerList();
ActionEvent e = null;
// Process the listeners last to first, notifying
// those that are interested in this event
for (int i = listeners.length-2; i>=0; i-=2) {
if (listeners[i]==ActionListener.class) {
// Lazily create the event:
if (e == null) {
String actionCommand = event.getActionCommand();
if(actionCommand == null) {
actionCommand = "FontChanged";
}
e = new ActionEvent(FontChooserPanel.this,
ActionEvent.ACTION_PERFORMED,
actionCommand,
event.getWhen(),
event.getModifiers());
}
// here registered listener executing
((ActionListener)listeners[i+1]).actionPerformed(e);
}
}
}
//!!! here your event generator
class MyPanelComponentsActionListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
//do something usefull
//.....
fireActionPerformed(e);
}
}
....
}

Get my Actions to see my other objects

I have a JLabel that has keybinded actions on it. I have defined some code for some of the Actions but, alas, there are other JLabels, a JPanel, and other things within the method (this is in main()) that I want my Actions to fool with.
I tried to change the Actions into taking parameters, but was not successful, how can I get my actions to take in parameters to manipulate? Is there any way? I have looked about but this is pretty specific and I see few good examples.
Here is a nice slab of my code:
/*Bunch of stuff I want my actions to interact with above - another JLabel, a JPanel*/
ImageIcon cursor = new ImageIcon("cursor.gif");
JLabel cursorlbl = new JLabel("", cursor, JLabel.CENTER);
Action goRight = new AbstractAction() {
#Override
public void actionPerformed(ActionEvent arg0) {
System.out.println("lol");
}
};
Action goLeft = new AbstractAction() {
#Override
public void actionPerformed(ActionEvent arg0) {
System.out.println("lol2");
}
};
Action goUp = new AbstractAction() {
#Override
public void actionPerformed(ActionEvent arg0) {
}
};
Action goDown = new AbstractAction() {
#Override
public void actionPerformed(ActionEvent arg0) {
System.out.println("lol2");
}
};
cursorlbl.setFocusable(true);
cursorlbl.getInputMap().put(KeyStroke.getKeyStroke("RIGHT"),
"pressed right");
cursorlbl.getInputMap().put(KeyStroke.getKeyStroke("LEFT"),
"pressed left");
cursorlbl.getActionMap().put("pressed right", goRight);
cursorlbl.getActionMap().put("pressed left", goLeft);

You can declare each action as a subclass (this starts to separate MVC anyways), and each item you want to manipulate a field in the parent class. Example:
// Parent Class
public class ParentClass{
//Field you want to mess with in your action
JLabel cursorlbl = new JLabel("");
// Action that does things
public class MoveAction extends AbstractAction{
char direction;
//Constructor for action
public MoveAction(char direction){
this.direction = direction;
}
#Override
public void actionPerformed(ActionEvent arg0) {
int change = 0;
// Figure out how you'll be changing the variable
if(direction == 'u' || direction == 'r'){
change = 1;
} else{
change = -1;
}
// Apply the change to the correct variable
if(direction == 'u' || direction =='d'){
cursy += change;
} else{
cursx += change;
}
//Example how you can access the parent class's fields
cursorlbl.setLocation(cursx, cursy);
}
}
}
Then to set your actions, you just create instances of your subclass:
contentArea.getActionMap().put("pressed right", new MoveAction('r'));
contentArea.getActionMap().put("pressed left", new MoveAction('l'));

Declare other components you wish to see in your actions as final. That will make actions see them.
More info here

You should be able to pass them in like this:
// note that the JLabel is now final
final JLabel cursorlbl = new JLabel("", cursor, JLabel.CENTER);
Action goRight = new AbstractAction() {
#Override
public void actionPerformed(ActionEvent arg0) {
System.out.println(cursorlbl.getText()); // has access to JLabel because it's scoped to the method/class
}
};
Note that doing this can cause some maintenance issues and you should try to document things that might be unclear for future developers (and yourself two weeks from now!)