CODEWITHSUNDEEP
c++user-interfacelayoutqt4
houbysoft
houbysoft

Reputation: 33392

GtkVBox Qt equivalent

In GTK, I used to have a window to which I gtk_container_add()'d a GtkVBox. Then I could pack widgets I wanted to the GtkVBox to have them appear in the window.

Now I've decided to try out Qt, but I can't seem to figure out how to do this in Qt.

Right now what I've done is create a QMainWindow, but I found that you can only pack one main widget into it, which is obviously quite limiting. So I wanted to create something like the GtkVBox and use that as the main widget and then add other widgets to this box.

What I've found by Googling are however only the Q3VBox widget, which seems to be what I want, but is deprecated, and the QVBoxLayout.

I tried to use the QVBoxLayout, but it tells me that I cannot change the layout of my QMainWindow since it already has a layout.

Edit: Here is how I do it (this is in the constructor):

box = new QVBoxLayout;
setLayout(box)

It compiles fine, but during runtime, it prints on the console: QWidget::setLayout: Attempting to set QLayout "" on HCGWindow "", which already has a layout (HCGWindow is my app's window, which is a subclass of QMainWindow)

So, how can I create something similar to a GtkVBox in Qt, and if the solution is the Q3VBox, why is it deprecated and what other thing should I use?

Thanks

Upvotes: 0

Views: 244

Answers (2)

Live
Live

Reputation: 2001

In fact, here is the recommended solution provided by the Qt documentation.

You should create a QVBoxLayout and add the widgets you want in it. After that, you set the layout on another empty widget and then you set this widget as the central widget of the QMainWindow subclass. Here is an example in code:

QWidget* widget1 = new QWidget(); // This could be anything subclassing QWidget.
QWidget* widget2 = new QWidget();

QVBoxLayout* layout = new QVBoxLayout();
layout->addWidget(widget1);
layout->addWidget(widget2);

QWidget* central = new QWidget(); // Only a containing QWidget.
central->setLayout(layout);

this->setCentralWidget(central);

Now, you QMainWindow subclass should have the two QWidgets in it, arranged in a QVBoxLayout.

Note here that I did not give any parent to anyone. You could have done it, but when you call addWidget or setCentralWidget, the ownership of the widget (and the layout) is given to the containing class.

If you read a bit about Qt, you'll know that this allows the parent to destroy his children when he is about to be destroyed itself.

Finally, note that QMainWindow is an exception and, from what I know, is the only class with setCentralWidget as a method. If you attempt to create a QWidget subclass, you will be able to use setLayout (as shown in the example above).

Hope this helps.

Upvotes: 2

Vladimir Lagunov
Vladimir Lagunov

Reputation: 1905

Try to create QVBoxLayout instance, add your widgets to it and add (not replace) this layout to main window's layout.

Note, QLayout class has no member addLayout, but subclasses has one.

Firstly you must get and remember classname of main window's layout:

qDebug(this.layout()->objectName);

Then add your QVBoxLayout to window's layout:

dynamic_cast<YourWindowLayoutClass>(
    this.layout())->addLayout(your_qvboxlayout_object);

I hope it will work.

Upvotes: 0

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