I have a button followed by a QGridLayout full of widgets.
I want to show/hide QGridLayout at every button click, but reading documentation of QGridLayout I see there's no show()/hide() implementation, also no setVisible() method available.
How do I achieve this?
Layouts only affect the size/position of the widgets added to them - for visibility (and anything else - event handling, focus, enable+disable) you care about the parent widget, as mentioned above. QLayout::parentWidget() gives you the widget which owns the layout, which you can then show and hide.
You didn't mention which version of Qt you're using. (I'm looking at the 4.4 documentation.)
I haven't tried this, but here are two ideas:
QGridLayout inherits the function QLayoutItem::widget(). If your layout is a widget, this will return a QWidget* on which you can call show() or hide().
If your QGridLayout is not a QWidget, you can nest it within a QWidget, and you can show() / hide() that widget instead.
I assume you have multiple QGridLayout instances, only one should be visible based on the button that has been clicked. You can use a QStackedWidget for this:
The QStackedWidget class provides a
stack of widgets where only one widget
is visible at a time.
Then, for each widget in the QStackedWidget you should associate a separate QGridLayout.
See the Qt documentation for more details
Related
I am new to Qt and I need to implement a monitoring interface with the following considerations:
I have a main window, on which I should put multiple screens, qsplitter appears to be the best solution.
The interface provides user with the option of changing the number of cameras, so QSplitter should be created/re-created during run time.
The problem is that I have too many cameras to pre-define widgets for them, so I need to create QSplitter UI instances dynamically.
The problem is that I can't find QSplitter classes when using Qt Designer and creating QSplitter class programatically is not working as MainWindow has been created through Qt Designer (.ui).
I would like to hear any suggestions regarding this issue, if there are better approaches, please let me know.
In Qt Designer, the QSplitter is not a widget, but a Layout.
Select the widgets you want to include in the two splitter areas, then select Layout from the context menu (right mouse button) - you will find two entries Layout Horizontally in splitter and Layout Vertically in splitter to group the widgets in a vertical or in a horizontal splitter.
QSplitter isn't a strict UI element, it's essentially a parent element that controls child elements. If you want to do it through Designer you'd probably run into headaches, but the basic gist is you select a number of widgets to be controlled by it, and click the Layout Horizontally/Vertically in splitter button which is in the layout buttons group.
What you might be best doing is creating your child elements programmatically, creating your splitter programmatically, adding the child widgets with someSplitter->addWidget(...). In the Qt docs there's some sample code for this:
QSplitter *splitter = new QSplitter(parent);
QListView *listview = new QListView;
QTreeView *treeview = new QTreeView;
QTextEdit *textedit = new QTextEdit;
splitter->addWidget(listview);
splitter->addWidget(treeview);
splitter->addWidget(textedit);
http://doc.qt.io/qt-5/qsplitter.html#details
And if you really want to do it in Designer there's a guide here: http://www.bogotobogo.com/Qt/Qt5_Splitter.php
Although QSplitter is a widget, you can't create one directly in Qt Designer. It is only available for laying out pre-existing widgets - which does not fit your use-case, since you need to create child widgets dynamically.
However, you can work around this limitation by using widget promotion. This is a simple mechanism that allows you to add substitute classes to represent widgets that are not directly available in Qt Designer. The idea is that you add a widget that is most similar to the one you actually want (e.g. a QFrame is most similar to QSplitter) and then promote that to the substitute class which you have defined in your own header file. When uic finally generates the code, it will use your substitute class instead of the class of the widget added in Qt Designer (which just acts as a placeholder).
Note that when you create your substitute class in the Promoted Widgets dialog, the base class should be a QFrame, not a QSplitter. This is because you are extending a QFrame (i.e. your placeholder widget), rather than a QSplitter. Of course, you can define your substitute class to be anything you like.
Image is easier to understand.
I am working on a hide/show feature for my console in my Qt GUI application. The console consists of 2 widgets; QLabel and QTextEdit. Do I need to add the QLabel and QTextEdit to a QWidget in order to show/hide them, or is there a better way?
So basically I am looking for a container such as 'JPanel' in Java...
Do I need to add the QLabel and QTextEdit to a QWidget in order to show/hide them, or is there a better way?
Multiple methods are possible here. You can, as you suggest, create a parent QWidget and add the QLabel and QTextEdit to a QWidget. Calling show and hide on the parent widget will affect its children.
Another method would be to have a slot function, which when an action is called, the slot calls show / hide on the 2 widgets.
Neither is right or wrong and depends upon the overall design of your application.
Ok, I think you need to use a layout (horizontal / vertical):
The simplest way to arrange objects on a form is to place them in a
horizontal or vertical layout. Horizontal layouts ensure that the
widgets within are aligned horizontally; vertical layouts ensure that
they are aligned vertically.
Horizontal and vertical layouts can be combined and nested to any
depth. However, if you need more control over the placement of
objects, consider using the grid layout.
My problem:
I want to customize the way the title bar works and looks for my application.
My idea:
I created a new QWidget form in Qt Designer and added a QWidget to it. I added the following code in constructor:
setAttribute(Qt::WA_TranslucentBackground);
setWindowFlags(Qt::FramelessWindowHint);
QGraphicsDropShadowEffect* effect = new QGraphicsDropShadowEffect();
effect->setBlurRadius(20);
effect->setXOffset(0);
effect->setYOffset(0);
setGraphicsEffect(effect);
which makes the outer widget transparent and adds shadow to my inner widget. From this on I can create a custom title bar widget which I can implement however I want.
This is the result:
My issue
I want to make this usable from the designer as a main window and the QWidget doesn't allow me to add FROM THE DESIGNER tool bars, menu bar and status bar.
What I thought about was adding a QMainWindow widget as a child widget for the outer QWidget(which is transparent and acts as support for my shadow(the shadow is drawn on it)). I did this successfully but only from code:
QMainWindow *centralwidget = new QMainWindow();
centralwidget->setStyleSheet("background-color: lightgray;");
centralwidget->setGeometry(0, 0, 50, 20);
centralwidget->setWindowFlags(Qt::Widget);
this->layout()->addWidget(centralwidget);
QMenuBar *menuBar = new QMenuBar(centralwidget);
menuBar->addAction("Action");
QStatusBar *statusBar = new QStatusBar;
statusBar->showMessage("Status bar here");
centralwidget->addToolBar("tool bar");
centralwidget->setMenuBar(menuBar);
centralwidget->setStatusBar(statusBar);
This is the result:
My question:
How can I achieve this result from Qt Designer? Is it possible to promote a QWidget to QMainWindow? I cannot think to another way of doing it... It is really important for me to make it usable from Qt Designer because I intend to make it a template widget and be able to create e.g. a new QCustomMainWindow form Qt Creator just like you can create a QWidget or a QMainWindow.
Please help!
Here is another SO question similar to yours: Qt4: Placing QMainWindow instance inside other QWidget/QMainWindow
Just adding on to my original comment:
Start with a QMainWindow, and then apply the appropriate flags to it. QMainWindow is a subclass of QWidget. If it can't be done easily in the designer, it is pretty painless to do in code. Do it in your constructor right after the ui->setup() call.
Start with QMainWindow
Customize Window Flags
So in the constructor in mainwindow.cpp, you put
http://qt-project.org/doc/qt-5/qt.html#WindowType-enum
this->setWindowFlags(Qt::Widget);
This is the default type for QWidget. Widgets of this type are child
widgets if they have a parent, and independent windows if they have no
parent. See also Qt::Window and Qt::SubWindow.
// or if you want to apply more than one you, "or" it together, like so:
this->setWindowFlags(Qt::FramelessWindowHint | Qt::WindowStaysOnTopHint | Qt::Tool);
Try out a couple of those and see what you like.
Customize Widget Attributes
There are also Widget Attributes, that give you strong control over how your widgets look like and behave.
http://qt-project.org/doc/qt-5/qt.html#WidgetAttribute-enum
Qt Style Sheets
In addition to all the flags and attributes above, you can also modify a ton of it with stylesheets:
http://qt-project.org/doc/qt-5/stylesheet-reference.html
this->setStyleSheet("background: #000000;");
Qt Designer Custom Widgets
And also if you are interested in making this a reusable thing in Qt Designer, you can make it into a Qt Designer plugin, or custom widgets.
http://qt-project.org/doc/qt-4.8/designer-using-custom-widgets.html
http://qt-project.org/doc/qt-4.8/designer-creating-custom-widgets.html
QMdiArea and QMdiWindow
Another path to look into besides using QMainWindow is QMdiSubWindow
http://qt-project.org/doc/qt-5/QMdiSubWindow.html
I have a QHBoxLayout horizontal layout with a lot of list widgets added to it.
And although I call setMaximumWidth(300) and setMinimumWidth(300) for the list widgets, once they don't fit on the window, they start to shrink.
I would like to have a scroll bar instead. Is this possible?
Yes, if you put the Layout inside a parent widget, and that parent widget inside a QScrollArea.
QScrollArea Documentation
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
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.
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.