I am overriding the QPlainTextEdit to become a single line edit widget. In other words I want it to look like a QLineEdit but to have the extended functionality of QPlainTextEdit, such as text formatting etc.
My only trouble so far is that I do not know how to pass focus to the next/previous widget when I press Tab/Shift+Tab when the widget derived from QPlainTextEdit is in focus. I have started with overriding keyPressEvent to capture Tab key being pressed, but then what? How to change the focus from the widget?
I can only think of too complicated solutions (such as signalling to the parent that the focus should change, but this seems as stupid overkill). I bet there must be a very simple solution to this problem.
Set the tabChangesFocus property of your QPlainTextEdit object to true by using the QPlainTextEdit::setTabChangesFocus function.
I accepted the answer by thuga which is the simplest way. However I found also another one which might be more generic for widgets that do not have tabChangesFocus property. Override keyPressEvent like this:
def keyPressEvent(self, event):
if event.key() == QtCore.Qt.Key_Tab:
self.parent().focusNextChild()
elif event.key() == QtCore.Qt.Key_Backtab:
self.parent().focusPrevChild()
There are two things you can try:
Create QAction and add it to the widget. Set QShortcut to the action with QKeySequence(Qt::Key_Tab). Connect the action whith slot which changes the focus.
or
Use directly new QShortcut(QKeySequence(Qt::Key_Tab), widgetPtr, SLOT(changeFocus()));
So there is no need now to inherit your control only to capture keyPressEvent. Note that you may need to change the shortcut context for best match to your requirements.
Related
Is it somehow possible to add to each Item in a QListview a Button which is deleting the Object onClick? As shown in the following Picture:
EDIT: As I'm new in QT it would be nice to have some example, to understand it better. And as it seems there are three different Ways? What will be the best? Do use a QAbstractItemView?
Yes. You'll need to use:
QAbstractItemView::setIndexWidget ( const QModelIndex & index, QWidget * widget )
QListView inherits QAbstractItemView and when you're trying to customize list/tree views that's usually the place to look. Be careful though, without a delegate this doesn't scale very well. Check out this thread: http://www.qtcentre.org/threads/26916-inserting-custom-Widget-to-listview
You can also go for a generic approach that can work on variety of containers, including the underlying model of your list view.
Each item in the list has a requestRemoval(Item*) signal and a removeMe() slot, connect the X button to the removeMe() slot in each item constructor, in removeMe() you emit the requestRemoval(this) signal, which is connected to a removeHandler(Item*) slot in your "parent" object upon creation of that item, which receives the pointer of the item which has requests deletion, and removes it from the underlying container being used.
Basically, pressing the remove button causes that particular item to send a pointer of itself to the parent's remove handler which removes that entry.
EDIT: Note that this is a generic approach, as noted in the comments below it can be applied without signals and slots as well, and even though it will work it is not the most efficient solution in your particular case.
I have a QListWidget and I have set it to accept drops, the mode to be DragDrop etc and I can move QListWidgetItems all around the place (inside the QListWidget of course).
I like this behavior and I want it to let it as is, but I also want my QListWidget to accept drops from a QTreeWidget as well. If I attempt to reimplement the dropEvent() of my QListWidget then I lose the default behavior.
Is there any way to just extend the current behavior so as to have both drag-drop between listwidget items and drag-drop from the treewidget to the listwidget or I have to completely re-write both behaviors in my dropEvent() reimplementation?
Thanks a lot for any answers :)
Two ways:
implement a standalone event filter and make it act upon QEvent::Drop. Install it on your original QListWidget. Return false so that the original dropEvent() handler is called afterwards.
inherit from QListWidget, reimplement dropEvent(evt) and as a last statement, call QListWidget::dropEvent(evt);. Your original behavior will be retained.
No.
Subclass QListWidget, reimplement
virtual void QListWidget::dropEvent ( QDropEvent * event )
and explicitly call
QListWidget::dropEvent(event);
whenever you need the default behavior.
How to call a parent class function from derived class function?
I'm working on a custom Qt button that allows you to edit the text on the button if you double click it. When the button is double clicked, a QLineEdit appears where the text on the button is allowing the user to edit the text on the button. My requirement is that if the user clicks anywhere in the application window, the QLineEdit should disappear and cancel the edit operation. This works in some cases. Specifically, it works if I click on anything that is capable of text entry. Other portions of the window don't work as expected. I'll click on a blank portion of the application window, and the QLineEdit retains its focus. How can I remove its focus in these cases?
I've found a solution that seems to work, though I'm still open to other options if there are any. I'm using PyQt4, so my example is in python:
Create a subclass of QLineEdit just so I have a new type. I don't want or need this behavior on all QLineEdit instances; just these specific ones.
class MyLineEdit(QtGui.QLineEdit):
pass
Now, in my QMainWindow subclass, I override the mousePressEvent() implementation. It gets the currently focused widget. If that widget is of type MyLineEdit, clear the focus.
class MyMainWindow(QtGui.QMainWindow):
def ...
def mousePressEvent(self, event):
focused_widget = QtGui.QApplication.focusWidget()
if isinstance(focused_widget, MyLineEdit):
focused_widget.clearFocus()
QtGui.QMainWindow.mousePressEvent(self, event)
def ...
This gets me the behavior I'm looking for so that if the user clicks anywhere on the application's window, the focus is cleared.
Edit: I did find one caveat to this. I have a QTreeView in the main window. If the user clicks on the tree view, focus is not removed from the text edit field.
Catch the clicked() signal of your parent widget and call yourLabel->clearFocus() (that unfortunatelly happens to not be a slot, making things more complicated) there.
I followed Grant Limberg instruction here but figured out that, in my case, a simple:
QApplication.focusWidget().clearFocus()
would fix the problem.
I'm not sure if this also works in Qt4 (I'm using PyQt5) but you can change the FocusPolicy of the QMainWindow or parent widget to clear the focus in the QLineEdit. As per https://doc.qt.io/qt-5/qwidget.html#focusPolicy-prop
I've changed the policy of my QMainWindow to Qt.StrongFocus and it worked like the functionality described in the question.
If done in C++ I would do something along the lines of:
connect(myWidgets->MyLineEdit, SIGNAL(returnPressed()), this, SLOT(onLineEditDone());
void onLineEditDone()
{
myWidgets->MyLineEdit->clearFocus();
}
For this particular case I would use editingFinished() instead of returnPressed(), probably, but I would NOT use textChanged(QString).
In my project I am using a custom circle-shaped button widget derived from the QWidget class. I have added several of these widgets to a parent widget.
When one of these custom buttons is clicked, how do I find out which one was clicked?
Adding custom button to parent widget:
void ShotViewCTRL::addShot(QString shotNanme)
{
ShotButton *btnShot=new ShotButton(this);
btnShot->shotName=shotNanme;
connect(btnShot,SIGNAL(Shot_Selected()),this,SLOT(SHOT_CLICKED()));
btnShot->CreateButton();
btnShot->show();
}
My parent widget is ShotViewCTRL (inherits from QWidget), the child widget is ShotButton (custom control, inherits from QWidget).
The control is working fine. It's sending sending to parent object. In my problem, I added the same custom control 10 times.
I need to find which control was clicked? Please help me find the solution.
I have referred to the Qt documentation to find the child widget, but I did't understand. Some sample code would be great.
QSignalMapper is what you are looking for. With QSignalMapper, you can add something like an Id (or even a pointer to the QButton itself) as additional data to the signal emittance and you have to adjust your slot so it takes additional data (ID or Pointer).
Then either distinguish in the slot itself by the id you give your objects some virtual function type() so you can distinguish with that or even try casting and catch errors (Tip: don't try the last method, it may work differently on different compiler).
You can use the QObject::Sender function to find which QObject sends the signal. Regarding the first warning in the doc, it's what you are searching for.
you specify different slots for different buttons with same signal.with that you can recognize the different button click
In my app have a window splitted by a QSplitter, and I need to remove an widget.
How can I do that? I can't find useful methods
It's not clear to me if you want to preserve the widget and put it somewhere else, or if you want to destroy the widget.
Destroying the widget: If you can
get a pointer to the widget, you can
simply delete it. The splitter will
safely be notified that its child is
being deleted and will remove it
from itself.
Preserving the widget: If you grab
the pointer to the widget, you can
simply set its parent to some other
widget and add it to another
widget's layout and it will show up
there. This is safe because the
QSplitter will be notified that one
of its children is being reparented.
If you want to set the parent to NULL (cjhuitt's answer) be aware that you are now responsible for cleaning up that memory because the widget no longer has a parent.
Many things in Qt cannot be "traditionally" removed. Instead call hide() on it and destruct it. From QSplitter documentation:
When you hide() a child its space will
be distributed among the other
children. It will be reinstated when
you show() it again.
I like Tuminoid's answer. But if you absolutely need it removed, try getting the widget you want to remove, and calling setParent( NULL ) on that widget. That's my best guess.
If you hold a pointer to the widget, then just delete it, or use deleteLater() if you want to be on the safe side.
If you do not have the widget pointer, use QSplitter::widget(int index) function. Then, you can use invoke its deleteLater() slot.
If you do not have the widget index, but you still know the widget objectName(), then QObject::findChild() is your only way to get the widget pointer.
I ran into the same problem. In Qt 4.8 to temporally hide one of the widget of a QSplitter I simply hide it. However it is not enough, as the splitter handle is still available to move. But the handle can be accessed and hidden as well:
frameA->setVisible(conditionA);
frameB->setVisible(conditionB);
if ( !(conditionA && conditionB) ) // if only 1 frame is visible
{
splitter->handle(0)->setVisible(false);
}
Another easy way to prevent the child widget from getting deleted is to use QSplitter.takeWidget(child). This is also the recommended way of removing the widget from a splitter. (Qt Documentation)