I'm trying to use the standard icons in Qt for a QToolButton but I have a problem. My code is:
m_buttonZoomPlus->setIcon(QStyle::standardIcon(QStyle::SP_DesktopIcon));
I get the error message :
cannot call member function 'QIcon QStyle::standardIcon(QStyle::StandardPixmap, const QStyleOption*, const QWidget*) const' without object
What does it mean? Do I Have to create an empty QStyle object and call the standardIcon function on it?
Besides, I found a list of standard icons here: http://doc.trolltech.com/main-snapshot/qstyle.html#StandardPixmap-enum
Is this list exhaustive or are there other standard icons? I'm looking for instance for a zoom-in/out icon and I've not yet been able to find it.
Thank you very much for you help.
It means standardIcon is not a static method so you can't call it that way. You need to construct a QStyle and initialize it appropriately then you can use that method to get a specific icon.
Edit: Jeremy is right. If you aren't changing the style or defining your own style you can simply use the following:
QApplication::style()->standardIcon(QStyle::SP_DesktopIcon);
Reference: http://doc.qt.io/qt-5/qstyle.html#standardIcon
Related
I have the following wxDialog parent window:
I have created that parent window by the following code:
settingsFrm settingsWindow(this, "Settings");
settingsWindow.ShowModal();
I have tried to use FindWindowByName to get the value of the first text ctrl as follow:
wxLogMessage(dynamic_cast<wxTextCtrl*>(settingsWindow->FindWindowByName("keywords_txt"))->GetValue());
But unfortunately, it doesn't work and gives me a runtime error.
I don't know if that method suitable to do what I want.
How to get the value/other of a control through its parent window?
From your comments, it seems like you expect the function to find the control from the name of the variable in your code which is not how it works and would be pretty much impossible.
FindWindowByName() uses the window name (and, as a fallback, label, but this is irrelevant here because text controls don't have labels anyhow), so for it to work you need to set the window name when creating the control, using the corresponding parameter of its ctor. This is very rarely useful in C++ code, however, as it's simpler to just store a pointer to the control in some variable and use this instead.
FindWindowByName() can often be useful when creating controls from XRC, however. If you do this, then you should specify names for your controls in XRC and pass the same name to this function.
How did you create the TextCtrl instance? You should have something like wxTextCtrl m_textCtrl1 = new wxTextCtrl(/// arguments); Accessing the value should be very easy, as wxString text = m_textCtrl1->GetValue(); You definitely don't need FindWindowByName just for what you are trying to do here.
please note: qt/c++ newbie here
Purpose:
I have a QDialog from which I want to return a result. I am aware of the QDialog::exec() which combined with setResult, results in the use of Accept() or Reject(),
but as the documentation page reads, the developers suggest to sue the QDialog return codes, implying that different values can be used although I have had no luck with this.
enum ReturnResult{
success=0,
fail=1
error=2
warning=3
}
How may I use the QDialog::setResult() function to send custom enum values to (as seen above),
as a result, back to the parent class, if this is not possible, any suggestion as to how I may solve this problem?
You can call QDialog::done(int res) to close a dialog with the desired result code, which then will be the return value of QDialog::exec().
The documentation for result() states that
In general returns the modal dialog's result code, Accepted or Rejected.
If I understand correctly, that means that even if the current implementation allows passing custom values, you cannot be certain that it won't change and break your code in the future.
In your case, simply add another signal to it and connect to it, or add your own field to your dialog and use it to pass the data.
I've just used cocos2d-x for creating some games. When I read the HelloWorld.cpp, I saw this line
Scene* HelloWorld::createScene()
That's strange for me. How does it work? A method named creatScene that takes no parameters and returns a pointer to a Scene ?
In different libraries, there are different methods to initialize library or some part of that. So, in this case, it maybe create a new context inside library and return it without any argument. It maybe needs no arguments (use defaults) it this step of get them from somewhere else like configuration file. And note that this is convenient to use this type of initializing. Like this:
rc = redis.Redis() #uses default values for server address
It is really an easy question even it cannot be called as question when you check the source code.
In cocos2d-x, CCScene always create this way.
1. create a Layer, which coded by yourself with a lot of other widgets.
2. create a Scene
3. add the layer to the scene
4. return the scene you create.
My question is best clarified by an example. I have QML with a Text{} item. In C++ I can get to this item and I have no problem using qobject_cast to turn anything into a QQuickItem*. But how do I turn it into the closest corresponding item so that I can call more specific methods directly like setText() the same way I might call setWidth()? I realize I can use the generic setProperty() method but I'm after the compile time checking that casting offers.
I'm after a more general answer for finding the correspondence between QML and their C++ classes, so that I can find out how to do this for Rectangles, MenuBars etc. I can't seem to find this in the docs. For those that prefer code examples:
auto text_object = app_item->findChild<QObject*>("myTextArea");
text_object->setProperty("text","New Text set from Code"); //THIS WORKS BUT...
auto text_qitem = qobject_cast<QQuickItem*>(text_object);
text_qitem->setWidth(128);
auto text_quick_text = qobject_cast<WHATGOESHERE???*>(text_object);
text_quick_text->setText("new Text for qml item"); //I WANT TO DO THIS
Q: but I'm after the compile time checking that casting offers.
qobject_cast does not offer any compilation-time checking. It is all runtime and dynamic, thus this request is not plausible. The context property is fine, or you could also get the class name with QMetaObject. Then, you could build a static LUT, but the effort may not be worth it overall...
All QML properties and methods are exposed to the meta-object system and can be called from C++ using Object::setProperty and QMetaObject::invokeMethod() respectively. invokeMethod parameters and return values passed from QML are always translated into QVariant values in C++:
QString msg("That's it");
auto text_object = app_item->findChild<QObject*>("myTextArea");
if (text_object)
QMetaObject::invokeMethod(text_object, "append", Q_ARG(QString, msg));
I would like to change the text of my UIBarButtonItem from another class (objective-C++) that I use in my project.
I have an IBOutlet myButton setup in myViewController and I can successfully do something like:
[ myButton setTitle:#"newTitle" ];
in myViewController.mm
Now I would like to do the same but from myCppClass that I use in my project.
Is there a way for myCppClass to access myViewController's myButton?
Shall I use some type of delegation mechanism?
I am pretty new to Ios and objective-C.
Thanks,
Baba
Create a method within your myViewController class to change the button title, then call that method from myCppClass by following the instructions described in this answer:
How to call method from one class in another (iOS)
https://stackoverflow.com/a/9731162/2274694
The short answer is, don't. You should treat a view controller's views as private. Instead, add a method to your VC like changeButtonTitle. Then call that method from from your other class.
The answers above are correct, but from your comments I suspect you aren't yet happy.
If you are super lazy, and you don't mind the string being the same in all instances of the VC (which in practice is usually the case) you could simply write a getter and setter for the string name as a class variable in the destination class. That way you don't even need access to the actual instance of the class, just its name. Tacky but super easy.
As others have pointed out, don't try and modify the buttons on a different VC directly. Pass a message and have the owning VC do it when it loads.
Well, passing messages forwards (to a new VC) is very easy. At the bottom of every VC class code there is #pragma navigation section commented out which gives you a handle to the destination VC. Cast it to the proper type and you set properties in the destination VC instance. In your case, create a public property NSString which holds the button text in your destination VC, and set it in your navigation section. This could be any class, or even a delegate, but a simple string should work.
Passing messages backwards (to previous VCs) can work the same way but it starts to get messy. You can programatically step back through the stack of VCs to find a particular (instance of) a VC. One of the answers to Get to UIViewController from UIView? gives sample code for stepping back through view controllers.
But if its simply forward communication, passing messages or information through
(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
at the bottom of the VC code and the commented out lines below is very easy and safe.