I just cannot grasp the enum in class concept syntactically.
I am trying to disable QTextEdit's frame:
//in a header for my custom class where the main element is the textField
QTextEdit* textField;
...
//displaying it myCustomClass.cpp
textField = new QTextEdit(this);
textField->Shape = QFrame::NoFrame;
I get the error "invalid use of enum::Qframe::Shape". What is the correct syntax and why?
That's invalid C++: there's no such "Shape" member for QTextEdit. Moreover, Qt uses proper encapsulation, so the shape is not exposed by a member variable.
You have to call a method which sets the frame shape, and surprisingly enough, it's called setFrameShape!
textField->setFrameShape(QFrame::NoFrame);
Related
I'm sorry if this question is duplicate but i am really struggling with finding any answer.
Please take in mind that i am novice in c++ programmming.
My problem is this. I have an GUI made in QtCreator. There are two listeners binding keyReleaseEvent, one on main class (SuperFalcon) , one on QTextEdit ( which is separate and modified class ). I have QFrame which i would like to toggle hide/show on "Ctrl + f" key event. Since that QFrame (object name is findWidget) widget belongs to SuperFalcon->ui, there's no problem, everything works fine, problem starts when i try to make "Ctrl + f" in QTextEdit because it's separate event listener. Basically i tried this.
main class name is "SuperFalcon" so:
in superfalcon.h i've made an public static pointer like this:
public:
static QFrame *fWidget;
then in superfalcon.cpp, i firstly execute
ui->findWidget->hide(); and then
fWidget = ui->findWidget; hoping to get pointer on widget.
Next in my QTextEdit class in keyReleaseEvent function i've tried to get that pointer like SuperFalcon::fWidget->show() but i get undefined reference on it.
So , to make things simpler, i don't know how , if possible, to get reference of QFrame widget which is part of one class (SuperFalcon), from another class (QTextEdit class) in order to execute some commands on QFrame.
If it's not clear enough i can provide some code.
You must have a definition of any static member variable.
This definition has to be in a source file because of the one definition rule.
Simply add the line:
QFrame* SuperFalcon::fWidget;
to "superfalcon.cpp".
You have to initialize your static variable, in superfalcon.cpp:
QFrame* SuperFalcon::fWigdet = nullptr;
I know that cast should be avoided and I´m trying to do it, but I can´t see how to do it using a QToolBox.
The window I´m building has a QToolBox for the user chose which operation he wants to do and inside the toolbox are the specific parameters to each operation. The apply button is outside the QToolBox.
When the user clicks the apply button I have to get which operation he has chosen and its parameters.
The problem is that QToolBox currentWidget() method returns a QWidget that is a class that I can´t change. So I can´t use virtual methods or something like that. The only way I see to get the parameters is using cast.
Here is some code to show my problem:
class BaseOperation : QWidget {
public:
virtual int getParameter() = 0;
}
class Operation1 : public BaseOperation {
...
}
class Operation2 : public BaseOperation {
...
}
...
_ui->toolBox->addItem(new Operation1(this), "OP 1");
_ui->toolBox->addItem(new Operation2(this), "OP 2");
...
QWidget* curItem = _ui->toolBox->currentWidget();
BaseOperation* op = dynamic_cast<BaseOperation*>(op);
op.getParameter();
Is there a better way to do what I want? I thought of using the item index in the toolbox and a hash map to do it, but this does not seem very OOP.
You can track widget changes, map index to concrete Operation class (not using hashmap, but simple switch-case) and then static_cast<> it, but that's what dynamic cast does for you, basically.
Using dynamic cast is perfectly OK in this case, IMO.
A possible different approach that avoids casts entirely is to use setProperty("name", QVariant(value)) to associate the data you need to the widgets, and then get the data back from the current widget using property("name").toInt() - this avoids casts and defining separate classes if what you need is an integer value (or something else reasonably simple)
I have a QT-project (using C++) where instances of a certain user-defined QGraphicsItem called Person move around the scene. Sometimes those Persons interact so that some of them change color.
Now I want to put a text field in the window and display counts of how many I have of each color. But since the change occurs within the call to the Person::advance-method I want to create a text field that can be updated from within these.
I could easily display some text by adding the following code to my main.cpp:
QGraphicsSimpleTextItem *text1 = new QGraphicsSimpleTextItem;
text1->setPos(-200, -150);
text1->setText("This is an arbitrary English sentence");
scene.addItem(text1);
but I do not know how to access and alter the text of this variable text1 from within the advance-method of the Persons in my scene. What is a good strategy for this?
Should I create a global variable keeping track of the count, and if I do, how can I then update the text field? Or should the text not even be on my QGraphicsScene, but rather be defined in some other more appropriate place where it is callable from everywhere in the program? Is there a generic way of doing this?
You could subclass QGraphicsObject instead of QGraphicsItem, that would allow you to use signals from within the Person class. Then just emit a signal to a slot that counts the items and changes the text of text1.
What I would do is move your graphics view to a new QWidget type class (like QMainWindow). This is to make it easier to handle signals and slots, and it will also allow you to use member variables. It will also be cleaner than doing everything in main.cpp.
You could have your text1 variable as a member variable of this MainWindow class. This would make accessing it easy.
Your slot in the MainWindow class could look something like this:
MainWindow::countItems()
{
int redcount = 0;
int greencount = 0;
int bluecount = 0;
// iterate through your `Person` items and check their colors and count them
text1->setText(QString("Red items: %1, Green items: %2, Blue items: %3").arg(redcount).arg(greencount).arg(bluecount));
}
You can improve the logic, but this is just a basic example.
I am implementing a Code Editor into a program I am making following this tutorial
enter link description here
I am getting stuck on the "lineNumberPaintEvent" method. This is what I have
void LineNumbers::paintEvent(QPaintEvent *event) {
QPainter painter(this);
painter.fillRect(event->rect(), NUMBER_LINE_COLOR);
QTextBlock block = parent->armaEdit->firstVisibleBlock();
int blockNumber = block.blockNumber();
}
where "armaEdit" is a QPlainTextEdit widget in another class.
When I attempt to run this, I get the following error:
error: 'QTextBlock QPlainTextEdit::firstVisibleBlock() const' is protected
I have not come across this error yet, and I have no clue what is means, or what I am doing wrong. May someone please point out my error?
A protected method is one that the author of the class has marked with the "protected" keyword. It is only accessible to subclasses of the class (i.e. to code in a subclass of QPlainTextEdit, in this case).
Usually this is an indication that you shouldn't call that method, as it wasn't intended for use by any code other than QPlainTextEdit or its subclasses.
If you really need to call it, though, you could create a subclass of QPlainTextEdit, and call firstVisibleBlock() from within a method of that subclass.
straight to the point:
Im learning wxsmith and wxwidgets toolkit, i created some basic GUI containing one button and 2 static text fields. GUI is compilling ok so far. My frame name is proba2Frame, then im adding my own function which is not a member of any class but i declared in header file for proba2Frame that my function is a friend. Below is code of my function:
wxStaticText * dawajpointera()
{
wxStaticText * text;
text = proba2Frame.wxStaticText.StaticText1;
return text;
}
im getting error:
expected primary-expression before ‘.’ token
What exactly im doing wrong and how to get a pointer StaticText in case my solution is completely wrong ?
Thank You in advance
You make it sound like proba2Frame is the name of a class inheriting wxFrame?
If so, you're haveing problems because you haven't created an instance of proba2Frame, and you're trying to access a part of it that hasn't been constructed. Your main frame class is simply a template for your GUI, not the GUI itself.
The best way to go about it would probably be to take an instance of proba2Frame as a parameter-
wxStaticText* dawajpointera(proba2Frame *frame)
{
return frame->StaticText1;
}
Of course, that function itself was a bit pointless, but I'll assume that you're going to do something more involved with the pointer afterwards, and want it set to a pointer named text within the function for the sake of brevity.
void func(proba2Frame *frame)
{
wxStaticText *text = frame->StaticText1;
// Do something with text
}
If you're doing this, though, please consider making the function a method of proba2Frame.
wxStaticText is the name of a wxWidgets class. You should not be naming attributes of your frame 'wxStaticText'. Despite the code you have posted, I doubt that you have really done such a terrible thing. What you probably meant to write, I would guess, is:
text = proba2Frame.StaticText1;
I am guessing that the name of the attribute is StaticText1, a pointer to an instance of the wxStaticText class.