I didn't find a proper solution to this problem, so I hope somebody can give me an answer to my problem:
I am using a normal QTreeWidget, but as items I use an own subclass of QTreeWidgetItem (because I needed to store some other information in the item). Now I want to use the itemClicked() signal by the QTreeWidget, but I think my slot doesn't get any signal and I think it has to do with the signature of itemClicked(), since it sends a QTreeWidgetItem and of course not my own subclass.
Is it possible that QTreeWidget doesn't detect a click on my own subclass items?
Here is my connection:
connect(treeWidget, SIGNAL(itemClicked(QTreeWidgetItem *)), this, SLOT(displayTransformData(QTreeWidgetItem*)));
And here is my slot:
void GUI::displayTransformData(QTreeWidgetItem* item) {
cout << "test" endl;
Q_actorTreeWidgetItem* actor_item = dynamic_cast<Q_actorTreeWidgetItem*>(item);
vtkSmartPointer<vtkActor> actor =
vtkSmartPointer<vtkActor>::New();
actor = actor_item->getActorReference();
double* position = new double[3];
position = actor->GetOrigin();
x_loc->setText(QString(std::to_string( position[0]).c_str() ));
}
I'm already trying to cast the item that I could get from the signal into my own subclass, but the slot function is never called, because the test from my cout line doesn't appear in the console.
I'm very grateful for every help!
The problem is your incorrect SIGNAL specification,
SIGNAL(itemClicked(QTreeWidgetItem *))
You should probably see a warning message at the console along the lines of:
QObject::connect: No such signal
tree_widget::itemClicked(QTreeWidgetItem *) in ...
From the documentation the actual signal spec is
void QTreeWidget::itemClicked(QTreeWidgetItem *item, int column)
So, using the old Qt4 syntax you need
connect(treeWidget, SIGNAL(itemClicked(QTreeWidgetItem *, int)),
this, SLOT(displayTransformData(QTreeWidgetItem*)));
If possible, however, you should make use of the newer Qt5 signal/slot syntax
connect(treeWidget, &QTreeWidget::itemClicked, this, &GUI::displayTransformData);
Related
I am getting this error with connect function
QTimer timer;
QObject::connect(&timer, &QTimer::timeout,this, &MainWindow::draw);
timer.start(1000);
both timeout and draw are predefined functions.
How can I solve this?
Even If I use a different function like
Sprite *sprite = new Sprite(this);
QTimer timer;
QObject::connect(&timer, &QTimer::timeout,sprite, &Sprite::drawNextBall);
timer.start(1000);
void Sprite::drawNextBall(QPainter &painter)
{
qDebug() <<"Sprite::drawNextBall() called";
painter.drawEllipse(x, y, 15, 15);
}
As stated by the error message, signal and slot arguments should match. This is definitely not the case in your example as QTimer::timeout has not a QPainter& as its first argument:
The signature of a signal must match the signature of the receiving slot. (In fact a slot may have a shorter signature than the signal it receives because it can ignore extra arguments.) [1]
Secondly, QPainter should only be used to draw on a QWidget inside a QWidget::paintEvent:
Warning: When the paintdevice is a widget, QPainter can only be used inside a paintEvent() function or in a function called by paintEvent(). [2]
What you probably want is connecting the QTimer::timeout signal to the QWidget::update (MainWindow::update or Sprite::update).
Relevant reading material
Signals & Slots
QPainter - Detailed description
I've experienced a weird crash when trying to find a QLineEdit in a QFormLayout.
Firstly, I created a QFormLayout and set a name for it:
QFormLayout *charColLayout = new QFormLayout; charColLayout->setObjectName("charColLayout");
Then, I created a QLineEdit, modified it a bit and add it in to the layout, and I also give it a name:
QLineEdit *delim = new QLineEdit;
delim->setMaxLength(1);
delim->setMaximumWidth(100);
delim->setText("/");
delim->setObjectName("delEdit");
charColLayout->addRow("Delimiter", delim);
Afterward, in a completely different function, I re-searched that layout with findChild():
QFormLayout *charcoal = secondHoriField->findChild<QFormLayout *>("charColLayout", Qt::FindChildrenRecursively);
It should be noted that secondHoriField is just a normal QLayout which my QFormLayout is located in.
Finally, I attempted to find that QLineEdit:
QLineEdit *delimEdit = charcoal->findChild<QLineEdit*>("delEdit", Qt::FindChildrenRecursively);
if (delimEdit == nullptr) {cerr << "error\n";} //debug
string curDelim = qStrToStr(delimEdit->text());
And it surprisingly came down with a crash, and as the output shown, it's because the delimEdit is null.
18:06:10: Starting D:\...\build-cryptog-Desktop_Qt_5_15_2_MinGW_64_bit-Debug\debug\cryptog.exe ...
error
18:06:17: The program has unexpectedly finished.
18:06:17: The process was ended forcefully.
18:06:17: D:\...\build-cryptog-Desktop_Qt_5_15_2_MinGW_64_bit-Debug\debug\cryptog.exe crashed.
But when I switched the findChild() function for this rather bruteforce-y line:
QLineEdit *delimEdit = dynamic_cast<QLineEdit*>(charcoal->itemAt(1)->widget());
cerr << qStrToStr(delimEdit->objectName()) << endl; //debug line
The program ran fine, and it showed the same name I set for the QLineEdit:
18:12:02: Starting D:\...\build-cryptog-Desktop_Qt_5_15_2_MinGW_64_bit-Debug\debug\cryptog.exe ...
delEdit
18:12:11: D:\...\build-cryptog-Desktop_Qt_5_15_2_MinGW_64_bit-Debug\debug\cryptog.exe exited with code 0
Why did this happened?
Another note: qStrToStr() is a function I implement to convert QString to std::string, and I have hand-checked it.
While findChild is a QObject method the itemAt is a QFormLayout method.
QObject::findChild
QFormLayout::itemAt
With addRow you add an item to the QFormLayout. This does not make it a child in the context of the QObject.
QFormLayout::addRow
The purpose of the QFormLayout is to organize the positioning of QWidgets, it is not meant to serve as a container. Maybe you could check whether the top level QWidget (e.g. QMainWindow) holding the QFormLayout would be a better choice as a parent for the QLineEdit.
Assuming you have some kind of QMainWindow:
QMainWindow myMainWindow;
// ...
QLineEdit *delim = new QLineEdit(&myMainWindow);
delim->setObjectName("delEdit");
//...
In another location:
auto delimEdit = myMainWindow.findChild<QLineEdit*>("delEdit");
I have an application which contains such lines.
emit WindowAdded(settings->WindowType);//!!!!!!!!!!!!!!
MyWindow *widget = new MyWindow(0,settings,currentWindowIndex);
The signal changes value of currentWindowIndex, but it didn't work because of slot, it doesn't change its value in time. Some one advices me to use QEventLoop, but i don't understand how to do this. Give me an example, please.
Another part of the code:
connect(area,SIGNAL(WindowAdded(QString)),this,SLOT(addWindowOnTab(QString)));
void WorkSpace::addWindowOnTab(QString title)
{
qint32 i = TabsList->addTab(title);/////!!!!!!!!!!!!!!!!!!!!!!!!!
emit addedWindowIndex(i);
TabsList->setVisible(true);
}
connect(this,SIGNAL(addedWindowIndex(qint32)),area,SLOT(WindowIndexChanged(qint32)));
void MyMdiArea::WindowIndexChanged(qint32 index)
{
currentWindowIndex=index;
}
I think it can help.
MyMdArea is сlass inherited from QMdiArea, WorkSpace is a QWidget, TabsList is a QTabBar.
And there is another fact: I tried to understand execution sequence of slots and added some lines to code:
QLabel *n= new QLabel("1");
n->show();
after emiting WindowAdded signal
QLabel *n= new QLabel("2");
n->show();
after emiting addedWindowIndex signal
and
QLabel *n= new QLabel("3");
n->show();
after changing currentWindowIndex's value
and that is what i saw "1 2 3" and its exploded my brain. Maybe i don't understand something?
I have a widget containing a QSpinBox. This widget also has a QVector<int> Values. What I would like to do is get the QSpinBox to display values issued from Values only.
At first I thought that a new slot and signal in my widget would do the trick, something like
slot :
void ChangeSomeValue()
{
// QVector<int> Values;
// int Index;
int val = Values[ Index ];
emit( SomeValueChanged( val ) );
}
connects :
connect( UI->MySpinBox, SIGNAL( valueChanged(int) ), this, SLOT( ChangeSomeValue() ) );
connect( this, SIGNAL( SomeValueChanged(int ) ), UI->MySpinBox, SLOT( setValue(int) ) );
But then several problems arise :
QSpinBox emit another valueChanged after I call its setValue, resulting in an infinite loop (until my QVector explodes).
I still have to find a way to keep track of Index, depending on which of the QSpinBox arrows was clicked (up or down... I don't even think this is possible).
So my solution, with its problems, seems to be a dead end. Any idea?. I'd like to stick to QSpinBox, if possible.
Thanks !
[EDIT]
Subclassing :
class SpinBox : public QSpinBox
{
Q_OBJECT
public:
explicit SpinBox(const QVector<int> & values, QWidget * parent = 0) :
QSpinBox(parent),
mValues(values),
mIndex(0)
{
qSort(mValues);
setMinimum(mValues.at(0));
setMaximum(mValues.at(mValues.size() - 1));
setValue(mValues.at(0));
}
protected:
void stepBy(int steps) // re-implementaion
{
mIndex += steps;
mIndex = qBound(0, mIndex, mValues.size() - 1);
setValue(mValues.at(mIndex));
}
private:
QVector<int> mValues;
int mIndex;
};
I Would suggest writing your own class to do it by sub-classing QAbstractSpinBox.
Maybe take a look at the accepted answer on this question:
How to subclass QSpinBox so it could have int64 values as maxium and minimum
QSpinBox emit another valueChanged after I call its setValue, resulting in an infinite loop (until my QVector explodes).
You can prevent this by using QObject::blockSignals(). Make sure to unblock signals afterwards.
I still have to find a way to keep track of Index, depending on which of the QSpinBox arrows was clicked (up or down... I don't even think this is possible).
Well, I suppose you can store the old value in a member variable, and when QSpinBox emits valueChanged(), you can compare the new to the old value to figure out whether the up or the down arrow was pressed.
That said, I don't know if that's enough to make QSpinBox behave like you want, correcting the value after it was changed once is a bit hacky. Subclassing QAbstractSpinbox might be better indeed.
I used Qt Creator to make a "keyboard" window with sixty QPushButtons and one QLineEdit. How can I make the buttons to add characters into QLineEdit text box? If I press a QPushButton with the label 'Q' on it, I want the program to add the Unicode character 'Q' on the text box.
One way to do this would be to just connect the 'clicked' signal from all the buttons to a slot, and then handle the adding of the character there.
For example, if the all keyboard buttons are inside a layout called 'buttonLayout', in your MainWindow constructor you can do this:
for (int i = 0; i < ui->buttonLayout->count(); ++i)
{
QWidget* widget = ui->buttonLayout->itemAt( i )->widget();
QPushButton* button = qobject_cast<QPushButton*>( widget );
if ( button )
{
connect( button, SIGNAL(clicked()), this, SLOT(keyboardButtonPressed()) );
}
}
Then in the slot implementation, you can use QObject::sender(), which returns the object that sent the signal:
void MainWindow::keyboardButtonPressed()
{
QPushButton* button = qobject_cast<QPushButton*>( sender() );
if ( button )
{
ui->lineEdit->insert( button->text() );
}
}
OPTION 1 - Multiple signals and slots
Connect all pushbuttons clicked() signal to a slot
// Let button01 be the A
connect(ui->button01, SIGNAL(clicked()), this, SLOT(buttonClicked()));
...
// Let button 60 be the Q
connect(ui->button60, SIGNAL(clicked()), this, SLOT(buttonClicked()));
In the buttonClicked() slot you have to figure out which button was clicked and append the corresponding letter to the line edit.
void buttonClicked()
{
QObject* callingButton = QObject::sender();
if (callingButton == button01)
ui->lineEdit->setText(ui->lineEdit->text()+ "A");
...
else if (callingButton == button60)
ui->lineEdit->setText(ui->lineEdit->text()+ "Q");
}
OPTION 2 - Subclass QPushButton
You could subclass QPushButton in order to avoid the multiple ifs. In your subclass just catch the mouse release event and emit a new signal which will contain the button's text
void KeyboardButton::mouseReleaseEvent(QMouseEvent* event)
{
emit clicked(buttonLetter); // Where button letter a variable of every item of your subclass
}
Similarly connect the clicked(QString) signal with a slot
connect(ui->button01, SIGNAL(clicked(QString)), this, SLOT(buttonClicked(QString)));
...
connect(ui->button60, SIGNAL(clicked(QString)), this, SLOT(buttonClicked(QString)));
void buttonClicked(QString t)
{
ui->lineEdit->setText(ui->lineEdit->text()+ t);
}
I have created an application with a similar issue, trying to convert the qpushbutton text to the qlineedit itself. The key is how you initialize the buttons and to use polymorphism in your function. To create an emit signal wont work for individual characters. The .digitValue will work if the case if for numerics (which the buttons would be of type int), but qt doesnt have a character value (I should say after 6hrs of reading qt doc and another 4 of trying different combinations it would not work), I think it has to do with how many bits it takes to store each variable type in an array. I even tried converting the button->text to QString to use with the emit function as a signal prototyped.
I do not know what your button layout is, but I will give you a synopsis of what I did. I first created a global, static const char array containing all the letters needed e.g.
static const char vowelarray[] = "AEIOU";
Then initialized the QPushButtons with in the MainWindow function, using iteration, setting a for loop's terminating condition equal to the size char array (in your case 60?). This all depends on your button layout though. I personally created a void function (setLocation) for the button->setGeometry of each button and iterated the setGeometry, and then passed the function to the MainWindow Function, at end of fucntion. The following code was used to initialize the buttons, connect signals to slots, and use polymorphism to connect to lineedit.
for (int i = 0; i < 26; i++){
characterButton[i] = new QPushButton(chararry[i], this); `
characterButton[i] -> setStyleSheet("QPushButton{background: grey; color: brown}");
connect(characterButton[i],SIGNAL(released(),this,SLOT(characterPushed()));
}
setLocation();
Then created a void function (e.g. void MainWindow::characterPuched()) where the following code was used:
void MainWindow::characterPushed(){
QPushButton *characterButton = (QPushButton*) sender();
if (characterButton )
{
lineEdit -> setText(letters.insert(letters.size(), characterButton -> text()));
}
lineEdit -> setText(letters);
}
of course letters was a global variable as well as:
QString letters = "";
and of course the QPushButtons and the function were prototype in the header file as a private variables and slots, e.g.
private:
QPushButton *characterButton[26];
the variable 'letters' was used to extract and input text to and from the line edit for further functions throughout the application.
Best Luck!!``