I have a 2 widgets inherited from QDialog. One of these widgets is called by another widget.
I need to pass data from the parent widget to the child. For example, I want passing QStringList.
I can make signals and slots in both classes. Slot of parent widget class - transferList(QStringList) - filling my QStringList.
How should I make the signal and slot connection? The child widget, of course, knows nothing about the parent.
// .h-file of parent widget.
class ElectricIndicationDialog : public QDialog {
#include "PollIndication.h" // class of child widget
QSharedPointer <PollIndication> pollInd;
public slots:
void transferList(QStringList);
signals:
void listTfansfer(QStringList);
private:
QStringList sendList;
};
// .cpp-file of parent widget
pollInd = QSharedPointer <PollIndication>(new PollIndication());
pollInd->show();
void ConfIndication::transferList(QStringList lst) {
lst.append("str1");
lst.append("str2");
}
// .h-file of child widget
class PollIndication : public QDialog {
public slots:
void getList(QStringList);
signals:
void listGet(QStringList);
private:
QStringList recList; // We transfer data to it
}
You don't need a signal/slot for that: your parent knows the type of its child and has a pointer on it. So, you can call a method of PollIndication when you need to send data to your dialog.
void ConfIndication::transferList(QStringList lst) {
lst.append("str1");
lst.append("str2");
pollInd->changeTransferList(lst);
}
If your dialog is modal, you can also create your dialog only when needed and give your list as parameter of the constructor.
void ConfIndication::transferList(QStringList lst) {
lst.append("str1");
lst.append("str2");
PollIndication* pollInd = new PollIndication(lst, this);
pollInd->exec();
}
It is normally a bad idea to make a parent class to know what are their children....
you can in the parent class define an abstract method (think about some pure virtual) so every childclass is forced to implement it... after that, the parent class can invoke the method and the child will implement the login depending on how it must react to it...
I've a custom dialog with several UI elements. Some TextFields are for numeric input. This dialog does not close when the escape key is hit and the focus is on any of the numeric text fields. The dialog closes fine when focus is on other TextFields which do not have this custom TextFormatter.
Here's the simplified code:
package application;
import java.text.DecimalFormat;
import java.text.ParsePosition;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Dialog;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.control.TextFormatter;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class Main extends Application {
#Override
public void start(Stage primaryStage) {
try {
TextField name = new TextField();
HBox hb1 = new HBox();
hb1.getChildren().addAll(new Label("Name: "), name);
TextField id = new TextField();
id.setTextFormatter(getNumberFormatter()); // numbers only
HBox hb2 = new HBox();
hb2.getChildren().addAll(new Label("ID: "), id);
VBox vbox = new VBox();
vbox.getChildren().addAll(hb1, hb2);
Dialog<ButtonType> dialog = new Dialog<>();
dialog.setTitle("Number Escape");
dialog.getDialogPane().getButtonTypes().addAll(ButtonType.OK, ButtonType.CANCEL);
dialog.getDialogPane().setContent(vbox);
Platform.runLater(() -> name.requestFocus());
if (dialog.showAndWait().get() == ButtonType.OK) {
System.out.println("OK: " + name.getText() + id.getText());
} else {
System.out.println("Cancel");
}
} catch (Exception e) {
e.printStackTrace();
}
}
TextFormatter<Number> getNumberFormatter() {
// from https://stackoverflow.com/a/31043122
DecimalFormat format = new DecimalFormat("#");
TextFormatter<Number> tf = new TextFormatter<>(c -> {
if (c.getControlNewText().isEmpty()) {
return c;
}
ParsePosition parsePosition = new ParsePosition(0);
Object object = format.parse(c.getControlNewText(), parsePosition);
if (object == null || parsePosition.getIndex() < c.getControlNewText().length()) {
return null;
} else {
return c;
}
});
return tf;
}
public static void main(String[] args) {
launch(args);
}
}
How do I close the dialog when escape key is hit while focus is on id?
The Problem
Before offering a solution I think it's important, or at least interesting, to understand why having a TextFormatter seems to change the behavior of the Dialog. If this doesn't matter to you, feel free to jump to the end of the answer.
Cancel Buttons
According to the documentation of Button, a cancel button is:
the button that receives a keyboard VK_ESC press, if no other node in the scene consumes it.
The end of that sentence is the important part. The way cancel buttons, as well as default buttons, are implemented is by registering an accelerator with the Scene that the Button belongs to. These accelerators are only invoked if the appropriate KeyEvent bubbles up to the Scene. If the event is consumed before it reaches the Scene, the accelerator is not invoked.
Note: To understand more about event processing in JavaFX, especially terms such as "bubbles" and "consumed", I suggest reading this tutorial.
Dialogs
A Dialog has certain rules regarding how and when it can be closed. These rules are documented here, in the Dialog Closing Rules section. Suffice to say, basically everything depends on which ButtonTypes have been added to the DialogPane. In your example you use one of the predefined types: ButtonType.CANCEL. If you look at the documentation of that field, you'll see:
A pre-defined ButtonType that displays "Cancel" and has a ButtonBar.ButtonData of ButtonBar.ButtonData.CANCEL_CLOSE.
And if you look at the documentation of ButtonData.CANCEL_CLOSE, you'll see:
A tag for the "cancel" or "close" button.
Is cancel button: True
What this means, at least for the default implementation, is that the Button created for said ButtonType.CANCEL will be a cancel button. In other words, the Button will have its cancelButton property set to true. This is what allows one to close a Dialog by pressing the Esc key.
Note: It's the DialogPane#createButton(ButtonType) method that's responsible for creating the appropriate button (and can be overridden for customization). While the return type of that method is Node it is typical, as documented, to return an instance of Button.
The TextFormatter
Every control in (core) JavaFX has three components: the control class, the skin class, and the behavior class. The latter class is responsible for handling user input, such as mouse and key events. In this case, we care about TextInputControlBehavior and TextFieldBehavior; the former is the superclass of the latter.
Note: Unlike the skin classes, which became public API in JavaFX 9, the behavior classes are still private API as of JavaFX 12.0.2. Much of what's described below are implementation details.
The TextInputControlBehavior class registers an EventHandler that reacts to the Esc key being pressed, invoking the cancelEdit(KeyEvent) method of the same class. All the base implementation of this method does is forward the KeyEvent to the TextInputControl's parent, if it has one—resulting in two event dispatching cycles for some unknown (to me) reason. However, the TextFieldBehavior class overrides this method:
#Override
protected void cancelEdit(KeyEvent event) {
TextField textField = getNode();
if (textField.getTextFormatter() != null) {
textField.cancelEdit();
event.consume();
} else {
super.cancelEdit(event);
}
}
As you can see, the presence of a TextFormatter causes the KeyEvent to be unconditionally consumed. This stops the event from reaching the Scene, the cancel button is not fired, and thus the Dialog does not close when the Esc key is pressed while the TextField has the focus. When there is no TextFormatter the super implementation is invoked which, as stated before, simply forwards the event to the parent.
The reason for this behavior is hinted at by the call to TextInputControl#cancelEdit(). That method has a "sister method" in the form of TextInputControl#commitValue(). If you look at the documentation of those two methods, you'll see:
If the field is currently being edited, this call will set text to the last commited value.
And:
Commit the current text and convert it to a value.
Respectively. That doesn't explain much, unfortunately, but if you look at the implementation their purpose becomes clear. A TextFormatter has a value property which is not updated in real time while typing into the TextField. Instead, the value is only updated when it's committed (e.g. by pressing Enter). The reverse is also true; the current text can be reverted to the current value by cancelling the edit (e.g. by pressing Esc).
Note: The conversion between String and an object of arbitrary type is handled by the StringConverter associated with the TextFormatter.
When there's a TextFormatter, the act of cancelling the edit is deemed an event-consuming scenario. This makes sense, I suppose. However, even when there's nothing to cancel the event is still consumed—this doesn't make as much sense to me.
A Solution
One way to fix this is to dig into the internals, using reflection, as is shown in kleopatra's answer. Another option is to add an event filter to the TextField or some ancestor of the TextField that closes the Dialog when the Esc key is pressed.
textField.addEventFilter(KeyEvent.KEY_PRESSED, event -> {
if (event.getCode() == KeyCode.ESCAPE) {
event.consume();
dialog.close();
}
});
If you'd like to include the cancel-edit behavior (cancel without closing) then you should only close the Dialog if there's no edit to cancel. Take a look at kleopatra's answer to see how one might determine whether or not a cancel is needed. If there is something to cancel simply don't consume the event and don't close the Dialog. If there isn't anything to cancel then just do the same as the code above (i.e. consume and close).
Is using an event filter the "recommended way"? It's certainly a valid way. JavaFX is event-driven like most, if not all, mainstream UI toolkits. For JavaFX specifically that means reacting to Events or observing Observable[Value]s for invalidations/changes. A framework built "on top of" JavaFX may add its own mechanisms. Since the problem is an event being consumed when we don't want it to be, it is valid to add your own handlers to implement the desired behavior.
The question already has an excellent answer, nothing to add. Just wanted to demonstrate how to tweak the behavior's InputMap to inject/replace our own mappings (as a follow-up to my comment). Beware: it's dirty in reflectively accessing a skin's behavior (private final field) and using internal api (Behavior/InputMap didn't make it into public, yet).
As Slaw pointed out, it's the behavior that prevents the ESCAPE from bubbling up to the cancel button if the TextField has a TextFormatter installed. IMO, it's not misbehaving in that case, just overshooting: the cancel/default buttons should be triggered on ESCAPE/ENTER if and only if no other had used it to change the state of the any input nodes (my somewhat free interpretation of consumed - had done some research on general UX guidelines that I can't find right now, embarassingly ...)
Applied to a form containing both a textField with textFormatter and a cancel button (aka: isCancelButton is true)
if the textField has uncommitted text, a cancel should revert the edit to the most recent committed value and consume the event
if the textField is committed it should let it bubble up to trigger the cancel button
The implementation of cancelEdit in behavior doesn't distinguish between those two states, but always consumes it. The example below implements the expected (by me, at least) behavior. It has
a helper method to decide whether or not is dirty (aka: the textField has an uncommitted edit)
a event handling method that checks for dirtyness, calls cancel and consumes the event only it had been dirty
a configuration method that tweaks the textFields inputMap such that the mapping is replaced by our own.
Note that this is a PoC: doesn't belong into helpers but into a custom skin (at the very least, ideally should be done by the behavior). And it is missing similar support for the ENTER .. which is slightly more involved because it has to take actionHandlers into account (which behavior tries to but fails to achieve)
To test the example:
compile (note: you need to reflectively access a private field, use whatever you have at hand - we all do, don't we) and run
type something into the field
press escape: the field's text is reverted to its initial value
press escape again: the cancel button is triggered
The example code:
public class TextFieldCancelSO extends Application {
/**
* Returns a boolean to indicate whether the given field has uncommitted
* changes.
*
* #param <T> the type of the formatter's value
* #param field the field to analyse
* #return true if the field has a textFormatter with converter and
* uncommitted changes, false otherwise
*/
public static <T> boolean isDirty(TextField field) {
TextFormatter<T> textFormatter = (TextFormatter<T>) field.getTextFormatter();
if (textFormatter == null || textFormatter.getValueConverter() == null) return false;
String fieldText = field.getText();
StringConverter<T> valueConverter = textFormatter.getValueConverter();
String formatterText = valueConverter.toString(textFormatter.getValue());
// todo: handle empty string vs. null value
return !Objects.equals(fieldText, formatterText);
}
/**
* Install a custom keyMapping for ESCAPE in the inputMap of the given field.
* #param field the textField to configure
*/
protected void installCancel(TextField field) {
// Dirty: reflectively access the behavior
// needs --add-exports at compile- and runtime!
// note: FXUtils is a custom helper class not contained in core fx, use your own
// helper or write the field access code as needed.
TextFieldBehavior behavior = (TextFieldBehavior) FXUtils.invokeGetFieldValue(
TextFieldSkin.class, field.getSkin(), "behavior");
// Dirty: internal api/classes
InputMap inputMap = behavior.getInputMap();
KeyBinding binding = new KeyBinding(KeyCode.ESCAPE);
// custom mapping that delegates to helper method
KeyMapping keyMapping = new KeyMapping(binding, e -> {
cancelEdit(field, e);
});
// by default, mappings consume the event - configure not to
keyMapping.setAutoConsume(false);
// remove old
inputMap.getMappings().remove(keyMapping);
// add new
inputMap.getMappings().add(keyMapping);
}
/**
* Custom EventHandler that's mapped to ESCAPE.
*
* #param field the field to handle a cancel for
* #param ev the received keyEvent
*/
protected void cancelEdit(TextField field, KeyEvent ev) {
boolean dirty = isDirty(field);
field.cancelEdit();
if (dirty) {
ev.consume();
}
}
private Parent createContent() {
TextFormatter<String> fieldFormatter = new TextFormatter<>(
TextFormatter.IDENTITY_STRING_CONVERTER, "textField ...");
TextField field = new TextField();
field.setTextFormatter(fieldFormatter);
// listen to skin: behavior is available only after it's set
field.skinProperty().addListener((src, ov, nv) -> {
installCancel(field);
});
// just to see the state of the formatter
Label fieldValue = new Label();
fieldValue.textProperty().bind(fieldFormatter.valueProperty());
// add cancel button
Button cancel = new Button("I'm the cancel");
cancel.setCancelButton(true);
cancel.setOnAction(e -> LOG.info("triggered: " + cancel.getText()));
HBox fields = new HBox(100, field, fieldValue);
BorderPane content = new BorderPane(fields);
content.setBottom(cancel);
return content;
}
#Override
public void start(Stage stage) throws Exception {
stage.setScene(new Scene(createContent()));
stage.show();
}
public static void main(String[] args) {
launch(args);
}
#SuppressWarnings("unused")
private static final Logger LOG = Logger
.getLogger(TextFieldCancelSO.class.getName());
}
I am new to Android developing and there it is not very clear to me the difference between the Click, Touch and Gesture classes in Android.
Is on the generalization of the other?
If you're talking about specific classes its always good to include the fully qualified name so as to avoid ambiguity.
Click is pretty generic so I assume your talking about
android.view.View.OnClickListener. This is an interface your widget class can implement to use the call back method onClick(). Any code inside the onClick() method is executed when you press that view (button).
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Perform action on click
}
});
Touch android.view.View.OnTouchListener
The onTouchListener is an interface that exposes the onTouch() callback method and gives you access to the android.view.MotionEvent members like ACTION_BUTTON_RELEASE. The MotionEvent class is very powerful for movement related behaviour.
Below example is from thread https://stackoverflow.com/a/11690679/1005142
imageButton.setOnTouchListener(new OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
if(event.getAction() == MotionEvent.ACTION_UP){
// Do what you want
return true;
}
return false;
}
});
Gesture android.view.GestureDetector.OnGestureListener
This class is used to pick up how the user gestures their finger with your UI. There is already a lot of information on the Android dev site in the gesture section http://developer.android.com/training/gestures/detector.html.
An example of using this class would be if you were writing fluidly with your finger on the keyboard where you need to listen for touch, movement and acceleration.
I have custom QWidget that contains custom QWindow. QWindow with OpenGL is used as a "connector" between render framework and Qt application.
Mouse and keyboard events are handled with overriding QWindow methods.
Pseudo-code:
class MyWindow : public QWindow
{
public:
MyWindow : QWindow() { /* GL stuff init*/ }
protected:
// mouse/keyboard event handling
// expose event handling
// resize event handling
// ...
};
class MyWidget : public QWidget
{
public:
MyWidget : QWidget()
{
auto window = new MyWindow();
auto container = createWindowContainer(window);
layout()->addWidget( container );
setAcceptDrops( true );
}
protected:
// overriding drop event, but is doesn't work
};
Question: how to handle drop events (it doesn't matter where)?
Problems:
QWindow doesn't provide virtual methods for drag-n-drop support.
QWidget::dragEnterEvent, QWidget::dropEvent (and similar) are not called.
QWindow still accept mouse events, even setMouseGrabEnabled( false ); is set.
Note: I found that call of setMouseGrabEnabled( false ); doesn't blocks mouse events handling in QWindow.
I found a solution:
It is necessary to install event filter on QWindow and process events there (eventFilter).
It is possible to install event filter on QWidget (container) but it doesn't work on OS X. Probably it is a bug in Qt, because under Win everything is fine.
I have two VM - View (inherited from Screen) and Edit (inherited from Screen). View is used to display grid with data and Edit - add/edit new items into grid.
In my ShellViewModel I have the following code to activate View.
public void WorkstationView()
{
this.ActivateItem(ServiceLocator.Current.GetInstance<WorkstationViewModel>());
}
In WorkstationViewModel when user clicks on the Create button the following code is invoked
public void CreateAction()
{
EditableObject = new WorkstationDto();
TryClose(true);
}
And there is a listener to Deactivated event property, see code below (InitViewModels is invoked in ShellViewModel constructor).
private void InitViewModels()
{
#region Init
WorkstationViewModel = ServiceLocator.Current.GetInstance<WorkstationViewModel>();
WorkstationEditViewModel = ServiceLocator.Current.GetInstance<WorkstationEditViewModel>();
#endregion
#region Logic
WorkstationViewModel.Deactivated += (o, args) =>
{
if (WorkstationViewModel.EditableObject == null)
{
return;
}
WorkstationEditViewModel.EditableObject = WorkstationViewModel.EditableObject;
ActivateItem(WorkstationEditViewModel);
};
#endregion
}
The problem here is a StackOverflow exception when I close Edit view (see create action).
“Since the Conductor does not maintain a “screen collection,” the activation of each new item causes both the deactivation and close of the previously active item.” Caliburn.Micro documentation
If you are using Conductor<T>, then ActivateItem(WorkstationEditViewModel); inside of the Deactivated handler is implicitly re-triggering the deactivation of the previous viewmodel - giving you an infinite loop. Try changing your conductor to inherit from Conductor<IScreen>.Collection.OneActive instead. However, you will still have two deactivations: the one from the original TryClose operation, and a second one when you activate the new screen. Overriding DetermineNextItemToActivate can help you avoid that.