I have started working with Qt again. What we want to do is to automatically generate graphical user interfaces. Therefore I have taken a closer look at the .ui file format (which is a XML based file format). These files are generated by the Qt Designer but can be easily be created by any other software. This part works so far.
But: we want to add some custom widgets. Creating custom widgets is also not that difficult. Some good websites exist out there: Creating Custom Widgets for Qt Designer, Using Custom Widgets with Qt Designer, (more hyperlinks held back),...
My question is rather: how can you implement custom widgets displaying custom items. Let's take one example. We have a QComboBox and a QSpinBox. The combobox has three items
A
B
C.
When selecting "A" I want the spinbox' minimum set to 1, maxiumum set to 9; when selecting "B" the spinbox' minimum should be set to 10, and its' maximum to 99; selecting "C" should set the spinbox' minimum to 100 and the maximum to 999. How is this done properly?
At the moment I set the data in a QTableWidget which is a helper class for me. Each row has three columns/cells:
item | min | max
-----+------+-----
A | 0 | 9
B | 10 | 99
C | 100 | 999
And I have my custom widget which contains the QComboBox and the QSpinBox. At runtime I tell the custom widget to take data/model from the QTableWidget and copy to itself by a method called setFriendContainer() [it's even a public slot which should be connected to a signal from the tablewidget which is emitted automatically]. Afterwards the tablewidget is not needed any more! I don't even want to show it to the user at all (this is why some size properties are set to 0; but it's partly still visible).
I think this is not really a clean way to implement it. What would be better/ an alternative? The items are also generated and should be contained in the same .ui file. Of course it would be possible to load it at runtime from another file, but I think this isn't rather an option. Do you think my workaround is ok, or is it too "ugly"? There are some examples where you can see how to add single custom properties, but I think this is something different - if you want to add whole containers (lists or tables of items, whatever). But including it in the .ui files might even be against the whole model/view concept?!
Any help welcome!
Thanks,
Matthias
I have added our data in a custom property in the form of XML. The data stores some coding information used in the widget. It's good to have the dynamic properties.
Remember that you are dealing with the properties of the widget. A UI file is nothing more than a description of the widgets, their properties, and their relation to each other in the hierarchy. A custom widget is no different than something like a QPushButton or QComboBox to Designer. The important thing is to encode the properties of your custom widget in a way that is understandable in the UI file.
You probably are best served by looking at the UI schema and making sure your widget can be described in a valid file. After that it's just to make sure that your properties behave correctly (i.e., that you can set properties in any order and get the same result). How you implement the widget is really up to you (make your own data structure, don't drag an "invisible" tree widget in).
Related
How do you use QStyledItemDelegate / QItemDelegate to permanently display a complex widget, i.e. to handle the Qt.DisplayRole, not just Qt.EditRole?
The documentation eludes to using paint()... but that's just way to complex! Let's take for example rendering a QTreeView or QTableVeiw inside of a QTableView cell.
There is QAbstractItemView.setIndexWidget(), but that is a bad idea as it only used to display static content (and whats the fun in static models?).
Note
I found part of the answer in another post, but it was only a small subset of the answer, so I thought it warranted a new post with proper question.
The key is to use QAbstractItemView.openPersistentEditor() to always keep the cell in edit mode.
Some additional key elements
The Qt.EditRole flag will need to be provided for the cells which use delegates.
QStyledItemDelegate.sizeHintChanged.emit(index) needs to be called anytime the size of the editor widget has changed.
Implementing QStyledItemDelegate.sizeHint() can be tricky and tedious (or you can do index.internalPointer().editor_widget.sizeHint() assuming you saved a reference of the editor to the internal pointer during QStyledItemDelegate.createEditor()
here is a good post on how to determine sizes: What are the mechanics of the default delegate for item views in Qt?
Caution
It should be mentioned that opening editors is costly, so if you have thousands of indexes and they are all loaded at once, it can take a while. There are many ways to mitigate this issue:
Load the model incrementally using a thread
Use Qt's fetchMore() mechanism
call openPersistentEditor incrementally (using a timer, or as they come into view for the first time)
call openPersistentEditor when the parent is expanded and closePersistentEditor when the parent is collapsed, and possibly restrict the use of expand-all on nodes with many children.
I'm totally new to Qt, so I'd be glad to have a wide answer.
Here I drew up some model:
We have a kind of table that contains:
an integer value with a spinbox.
a cell with three(not specifically) grouped radio buttons
Editbox
A button that interacts with this particular editbox.
Also we have 2 buttons to add and remove items from the table.
I did some google search and found out that it can be done via QTableView.
Is there any way to put such complex structures into a cell? Must it be a separate class inherited from QTableView?
If you're going to have up to a hundred or maybe a few hundreds of elements in the table, then use QTableWidget.
If you're going to have too many elements (about thousands), then go for QTableView, and learn model-view programming.
The reason why I recommend QTableWidget is because you're a beginner. All you have to do there is create a widget, and use setCellWidget() and you're done.
If you have thousands of rows, then you're gonna have to draw the widgets yourself using QStyledItemDelegate, which will paint the widgets inside your QTableView. This is a very painful thing to do, but there's no way around it. The reasons you can find here.
I see at least three options to implement that in Qt:
Use a QtableView or QTableWidget and insert some custom controls in it. See comments made be other persons to your post
Use a QGridLayout and fill it with your controls by line and column
Make your own QWidget to store and manage the line elements (the spinbox, edit field, radio button) using a QHBoxLayout. You can design this in QtCreator, it can have it's own .ui. This could make it easy to handle the interaction between each QWidget of a line (directly handled by your QWidget class). Later, you can put an instance of it for every line you need in a QVBoxLayout.
Personnaly, I would go with the last option, but it may not work smartly if the controls of each line have different content/size (see comments), then first options should be prefered.
I am creating my first app in QT and wanted to design a list. The listitem has two texts and one icon.
The problem is, i cant find any example or helping material, Only helping link i found is : Customize QListWidgetItem but i dont understand it. Although i have the same problem which this links points to...
What i understand is, i have two options:
1- Customize QListWidgetItem to use with QListWidget
2- Make some delegate to use with QListView
I was hoping to get started with option 1. Now in the link, some reply talks about "myItem" which is taking 2 texts as input. I want to know the implementation of "myItem".
In the link you posted, MyItem is just a normal QWidget. This means that you can create a widget in Qt Designer and then set that new widget you created as the widget that the QListWidgetItem should use for display. In the above example, MyItem takes two strings because there is a vertical layout with two labels in it (that's my assumption at least).
You should also note, and is discussed in the above link, that taking the approach of setting an item widget to use for every item in the list is an expensive thing to do in terms of performance and memory consumption. Because a QListWidget is a QListView, you can set an item delegate on it just like any other view and come out with a lighter weight solution (one instantiation of class vs. one instantiation for every item in your list)
I am newbie to Qt. I have to display a chunk of data in a QTableView and filter it column wise. For this I have used QSortFilterProxyModel, but as per requirement each column of the QTableView should have a drop-down list which shows unique values in that column. On selection of any of these values in the drop-down, only the rows having that particular value in the column should be displayed in the QTableView (Like you can do in Excel).
How would I implement this?
I had the same issue a week ago
I found a tutorial explaining how to do it. see link below
http://programmingexamples.net/wiki/Qt/Delegates/ComboBoxDelegate
Now my problem is how to retrieve the value of a specific combobox.
I think it is such a complex things to do in C++ and Qt display a combobox into a tableView.
For being a web developer at first I can tell that web language are better suited to do thoses kind of things.
But still some time performance matter and I tried to do it in C++ with Qt but it is not as easy as it seems to be in Web language.
This is very general question, and if I try to explain it all it will take pages, so it's better if you read the Qt model/view architecture documentation.
You can create your own class inherited from QTableView to create your customized table view. You have to use delegates for drop down functions and all. so read the QItemDelegate class documentation and documentation on subclassing delegates as well.
If you want to display it always and not just when editing, I would suggest setting a widget for the specific column like described in this thread: Qt - QTableView - Clickable button in table row
I've got a QTableView for which I want to display the last column always in edit mode. (It's a QComboBox where the user should be able to always change the value.)
I think I've seen the solution in the Qt documentation, but I can't find it anymore. Is there a simple way of doing it?
I think I could archive this effect by using openPersistentEditor() for every cell, but I'm looking for a better way. (Like specifying it only one time for the whole column.)
One way to get the automatic editing behaviour is to call the view's setEditTriggers() function with the QAbstractItemView::AllEditTriggers value.
To display the contents of a given column in a certain way, take a look at QAbstractItemView::setItemDelegateForColumn(). This will let you specify a custom delegate just for those items that need it. However, it won't automatically create an editor widget for each of them (there could in principle be thousands of them), but you could use the delegate to render each item in a way that makes it look like an editor widget.
There are two possibilities:
Using setIndexWidget, but Trolltech writes:
This function should only be used to
display static content within the
visible area corresponding to an item
of data. If you want to display custom
dynamic content or implement a custom
editor widget, subclass QItemDelegate
instead.
(And it breaks the Model/View pattern…)
Or using a delegate's paint method. But here you have to implement everything like enabled/disabled elements yourself.
The QAbstractItemModel::flags virtual function is called to test if an item is editable (see Qt::ItemIsEditable). Take a look at Making the Model Editable in the Model/View Programming documentation.
I can't see an easy way to do this, but you might be able to manage by using a delegate. I honestly don't know exactly how it would work, but you should be able to get something working if you try hard enough. If you get a proper delegate, you should be able to set it on a whole view, one cell of a view, or just a column or row.