Develop Reference

JavaFX - Accelerator not working when textfield has focus

In my application I have a screen where I use Accelerators. I'm using the function key F3 to execute an operation in my application. It works fine everytime, but when I click in any TextField on this screen the function key doesn't execute.
Here is the code where I set the Accelerator:
scene.getAccelerators().put(
new KeyCodeCombination(KeyCode.F3),
new Runnable() {
#Override
public void run() {
// do sth here
}
}
);
When I click my textfield and then hit the F3 function key it doesn't work.
Someone knows the solution?

This works for me using Java 1.8.0_45. However I encounter a similar issue with an editable Combobox field.
Edited:
Upon further investigation it does seem to occur with text field as well. I worked around it using the following custom class in place of text field:
public class ShortcutFriendlyTextField extends TextField{
public ShortcutFriendlyTextField() {
super();
addEventHandler(KeyEvent.KEY_RELEASED,new EventHandler<KeyEvent>() {
#Override
public void handle(KeyEvent event) {
//handle shortcuts if defined
Runnable r=getScene().getAccelerators().get(new KeyCodeCombination(event.getCode()));
if(r!=null) {
r.run();
}
}
});
}
}

This answer is based on tikerman's. I added the code to handle modifier keys.
if (!event.getCode().isModifierKey()) {
Consumer<KeyCombination.Modifier[]> runAccelerator = (modifiers) -> {
Runnable r = getScene().getAccelerators().get(new KeyCodeCombination(event.getCode(), modifiers));
if (r != null) {
r.run();
}
};
List<KeyCombination.Modifier> modifiers = new ArrayList<>();
if (event.isControlDown()) modifiers.add(KeyCodeCombination.CONTROL_DOWN);
if (event.isShiftDown()) modifiers.add(KeyCodeCombination.SHIFT_DOWN);
if (event.isAltDown()) modifiers.add(KeyCodeCombination.ALT_DOWN);
runAccelerator.apply(modifiers.toArray(new KeyCombination.Modifier[modifiers.size()]));
}
Edit: fix consumer spelling.

If you have accelerators setup else where, such as a MenuBar, using some of the other solutions will cause the shortcut to be executed twice.
In my case, using modifiers with my shortcut (SHIFT + F3) works while in focus in the text area, but not while using just an accelerator such as just F3.
I set mine up to only use the event handler for shortcuts that do not use a modifier.
public static final double JAVA_VERSION = Double.parseDouble(System.getProperty("java.specification.version"));
public static void makeInputFieldShortCutFriendly(Node node) {
//this bug wasn't fixed until 9.0
if (JAVA_VERSION < 9) {
node.addEventHandler(KeyEvent.KEY_RELEASED, (KeyEvent event) -> {
if (!event.getCode().isModifierKey()) {
if (!event.isAltDown() && !event.isShiftDown() && !event.isAltDown()) {
Runnable r = node.getScene().getAccelerators().get(new KeyCodeCombination(event.getCode(), KeyCodeCombination.SHORTCUT_ANY));
if (r != null) {
r.run();
}
}
}
});
}
}
Edit: No modifier shortcuts was fixed in Java 9. Given the popularity of JDK 8 right now, we should probably provide some backwards capatability or request users update there JRE to 9+.

I you are using JavaFx+Scene builder then just make a function that redirect all the event to the respective functions and then add this function to every element in the scene with OnKeyReleased event

SWT: Influence the detection of a Drag&Drop gesture (or: how to query the keyboard)

I am at an SWT application where one can rearrange controls within a shell (or any Composite for that matter) via drag&drop. That's basically no problem, DragSources and DropTargets are all in place and listeners attached accordingly. I even implemented a custom Transfer type for the sake of exercise. Pretty straightforward.
But now the requirement is that a drag should only be initiated, if the ALT key is pressed while the drag gesture is performed, otherwise nothing should be done. (The ALT key is an example, could be CTRL as well.)
So far, I see or have thought about the following approaches. All of them either don't work or are ugly.
\1. Intercept and cancel the DragDetect event
The idea is to cancel the event if the ALT key is not pressed with event.doit = false.
lblPos.addListener(SWT.DragDetect, new Listener() {
public #Override void handleEvent(Event event) {
if ((event.stateMask & SWT.ALT) == 0)
event.doit = false; // XXX: doit will not be evaluated
}
});
However, that doesn't work. The doit flag is apparently not evaluated.
\2. Intercept and cancel the DND.DragStart event.
class RowDragListener implements DragSourceListener {
public #Override void dragStart(DragSourceEvent event) {
if (/* ALT key not pressed */)
event.doit = false;
}
...
}
This has the opposite problem of appraoch 1. While the doit flag is properly evaluated and thus suitable to cancel the drag, there is no stateMask in the event that can be inspected for modifier keys. So the question arises, how can I query the keyboard directly (without installing KeyUp/Down event handlers)? What is the current up/down state of the ALT key?
\3. Combine 1 and 2
Inspect the stateMask in the DragDetect event, store the result somewhere, then react accordingly in the DND.DragStart event. This shouldn't be too hard, but I think it's ugly and should not be done this way. Instead of DragDetect, KeyUp/Down events could be captured and the last known state of the ALT key be stored.
\4. Override Control.dragDetect(Event) or Control.dragDetect(MouseEvent)
These methods ultimately create DragDetect events if they see the conditions for it fulfilled.
Check the event's stateMask and invoke the overridden method from the super class only if the desired modifier key is signalled. Problem here is, from the documentation it is not clear if this is the only code path that is treaded upon a drag gesture. In fact, these two methods are independent from each other (they don't invoke each other), so it's not even clear which one to override. These methods already are two separate ways to initiate a drag gesture. Who knows how many more ways are there? Overriding them all would be error prone, if possible at all, and certainly not clean.
So my questions are:
1. How would you do that? Any other ideas?
2. If approach 2 seems the most reasonable, how is the keyboard queried without resorting to event handlers?
(Sorry for the formatting of this post, i seem to be unable to grasp the syntax. Or maybe it's not my fault, who knows.)
UPDATE: There's one thing to note, which i noticed during the implementation. On Windows, ALT-Drag&Drop has the specific meaning of a link operation (as opposed to move or copy; cmp. DND.DROP_* constants). That's why, if you choose to use the ALT key in a similar fashion, be advised to include the following line at every reasonable occasion in the DropTargetListener.
if (event.detail == DND.DROP_LINK) event.detail = DND.DROP_MOVE;
I have this in the dragEnter, dragOver and dragOperationChanged listener methods and this works quite fine.

You can listen to SWT.DragDetect event, check the state mask and create the drag source only if conditions are met. Then pass the event to the newly created drag source by calling notifyListeneres(). After drag finishes the drag source has to be disposed.
Here is a snippet where drag is initiated only if alt is pressed, and uses text as transfer:
public static void main(String[] args) {
final Display display = new Display();
final Shell shell = new Shell(display);
shell.setLayout(new GridLayout());
shell.addListener(SWT.DragDetect, new Listener() {
#Override
public void handleEvent(Event event) {
if ((event.stateMask & SWT.ALT) != 0) {
final DragSource dragSource = new DragSource(shell, DND.DROP_MOVE);
dragSource.addDragListener(new DragSourceAdapter(){
#Override
public void dragFinished(DragSourceEvent event) {
dragSource.dispose();
}
#Override
public void dragSetData(DragSourceEvent event) {
event.data = "text";
}
});
dragSource.setTransfer(new Transfer[]{TextTransfer.getInstance()});
dragSource.notifyListeners(SWT.DragDetect, event);
}
}
});
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}

How to Subscribe to GUI Events in Other JFrames

What is the best practice for subscribing to events from another JFrame? For example, I have a "settings" form, and when the user presses okay on the settings form, I want the main form to know about this so it can retrieve the settings.
Thanks.
Here is my ideal interface:
public void showSettingsButton_Click() {
frmSettings sForm = new sForm(this._currentSettings);
//sForm.btnOkay.Click = okayButtonClicked; // What to do here?
sForm.setVisible(true);
}
public void okayButtonClicked(frmSettings sForm) {
this._currentSettings = sForm.getSettings();
}

Someone publishes an Event, that something has changed, here the settings. A subscriber that registered for this specifig event, gets notified about it and can do his work, here get the settings. This is called publisher/subscriber.
For this you can use Eventbus or implementing something smaller on your own.

One approach is to have only a single JFrame. All the other 'free floating top level containers' could be modal dialogs. Access the the main GUI will be blocked until the current dialog is dismissed, and the code in the main frame can check the settings of the dialog after it is dismissed.

For anyone interested, here is what I ended up going with. I'm not sure if it's the best way, but it is working for my purposes.
// Method called when the "Show Settings" button is pressed from the main JFrame
private void showSettingsButton_Click() {
// Create new settings form and populate with my settings
frmSettings sForm = new frmSettings(this.mySettings);
// Get the "Save" button and register for its click event...
JButton btnSave = sForm.getSaveButton();
btnSave.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent evt) {
SaveSettings(sForm);
}
});
// Show the settings form
sForm.setVisible(true);
}
// Method called whenever the save button is clicked on the settings form
private void SaveSettings(frmSettings sForm) {
// Get the new settings and assign them to the local member
Settings newSettings = sForm.getSettings();
this.mySettings = newSettings;
}
And if, like me, you are coming from a .NET perspective, here is the C# version:
private void showSettingsButton_Click(object sender, EventArgs e)
{
frmSettings sForm = new frmSettings(this.mySettings);
sForm.btnSave += new EventHandler(SaveSettings);
sForm.Show();
}
private void SaveSettings(object sender, EventArgs e)
{
frmSettings sForm = (frmSettings)sender; // This isn't the exact cast you need..
Settings newSettings = sForm.Settings;
this.mySettings = newSettings;
}

How do I make an ActionEvent and a KeyEvent fire the same action?

I'm writing an applet and want to figure out how to make a button and a key event cover the same bit of code. For this question, I'll call this button fireButton. The code for the action event would of course look like this:
public void actionPerformed(ActionEvent e) {
if (e.getSource() == fireButton) {
//all the code that pressing button executes
}
}
Now, I want pressing the 'enter' key to perform the same code that the action event handles, but I do not want to rewrite all the code again in a keyPressed method.
To be specific, I'm writing a battleship program, and the 'Fire' button takes input from two textFields, handles exceptions, and passes the input as parameters to a method that fires at a particular square in the grid. Ideally, pressing the enter key would function the same way as if I had pressed the fire button. Is there a way to make a certain method call an actionPerformed method? If not, what would be an elegant solution to the problem?

Create an Action
Add the Action to the JButton
Use Key Bindings to bind the Enter key to the Action
Read the Swing tutorial. There are sections on:
How to Use Actions
How to Use Key Bindings
If you are just talking about invoking the "Fire" button with the enter key then check out Enter Key and Button for a couple of approaches.

I suggest you put all the code in a separate method that receives all the relevant data from the event (if any) as parameters:
public void actionPerformed(ActionEvent e) {
if (e.getSource() == fireButton) {
Object relevantData0 = new Object(); // e.getSomething();
Object relevantData1 = new Object(); // e.getSomethingElse();
handleFireAction(relevantData1, relevantData2);
}
}
public void actionPerformed(KeyEvent e) {
if (e.getSource() == fireButton) {
Object relevantData0 = new Object(); // e.getSomething();
Object relevantData1 = new Object(); // e.getSomethingElse();
handleFireAction(relevantData1, relevantData2);
}
}
private void handleFireAction(Object relevantData0, Object relevantData1) { // Object relevantDat2, and so on
//all the code that pressing button executes
}
If you don't need any data from the event its even easier ;)
This way you just write your code once for both events. It's a general OO aproach.
Hope this helps.

Borrowing from MVC I would recommend you have a controller class which handles these sorts of requests. Then all you have to do is delegate to the controller in each event handler.
Like so:
public class BattleShipController {
public void handleFireAction() {
// ...
}
}
//-- in your UI class(es)
private BattleShipController _controller = new BattleShipController();
//-- in event calls:
_controller.handleFireAction();
If you post relevant code I can make further suggestions.

Disable back button in GWT

Is there a way to disable the Back button in a browser (basically clearing the History token stack) in GWT? Once I browse to a certain page in my application I want to make sure that the user can't use the back button to go back, but only be able to use links on the page to navigate the site.

You cannot disable a button just intercept it and change its return to something the browser does not understand.
This removes the history:
Window.addWindowClosingHandler(new ClosingHandler() {
#Override
public void onWindowClosing(ClosingEvent event) {
event.setMessage("My program");
}
});
To understand it see: http://groups.google.com/group/google-web-toolkit/browse_thread/thread/8b2a7ddad5a47af8/154ec7934eb6be42?lnk=gst&q=disable+back+button#154ec7934eb6be42
However, I would recommend not doing this because your it goes against good UI practices. Instead you should figure out a way that the back button does not cause a problem with your code.

Call the method below in the onModuleLoad().
private void setupHistory() {
final String initToken = History.getToken();
if (initToken.length() == 0) {
History.newItem("main");
}
// Add history listener
HandlerRegistration historyHandlerRegistration = History.addValueChangeHandler(new ValueChangeHandler() {
#Override
public void onValueChange(ValueChangeEvent event) {
String token = event.getValue();
if (initToken.equals(token)) {
History.newItem(initToken);
}
}
});
// Now that we've setup our listener, fire the initial history state.
History.fireCurrentHistoryState();
Window.addWindowClosingHandler(new ClosingHandler() {
boolean reloading = false;
#Override
public void onWindowClosing(ClosingEvent event) {
if (!reloading) {
String userAgent = Window.Navigator.getUserAgent();
if (userAgent.contains("MSIE")) {
if (!Window.confirm("Do you really want to exit?")) {
reloading = true;
Window.Location.reload(); // For IE
}
}
else {
event.setMessage("My App"); // For other browser
}
}
}
});
}

I found a way to make GWT ignore the back-button: Just add historyitem x if no historyitem was set and do nothing on x.
set a historyitem on startup
History.newItem("x")
in the ValueChangeHandler of History add the following:
String historyToken = event.getValue();
if (!historyToken.equals("x"))
History.newItem("x");

Window.addWindowClosingHandler(new ClosingHandler() {
#Override
public void onWindowClosing(ClosingEvent event) {
event.setMessage("My program");
}
});
That is not a fool proof solution. In fire fox I can press the back button and the onWindowClosing method is never invoked. The reason is that I have used History.newItem() and since history exists the back button or backspace buttons simply navigate through the browser history.
So....fix that :)

Put this in your index.html file:
window.open('html page(For example trial.html)', 'Name of the desired site', width='whatever you want',height='whatever you want', centerscreen=yes, menubar=no,toolbar=no,location=no,
personalbar=no, directories=no,status=no, resizable=yes, dependent=no, titlebar=no,dialog=no');