I'm trying to allow items from a QListWidget to be dragged to a "Trash" (A subclassed widget which accepts drops and does nothing with them).
I know that if I setDropAction(Qt.MoveAction), the items I am removing from the source will be automatically deleted. This works correctly.
My problem is that I also need to trigger an action that updates other widgets who depend upon the contents of the source.
It seems to me that the dropEvent happens before any items are actually removed from the source. I'm having a terrible time trying to figure out this problem. I've thought of two possible solutions:
Find a way to embed the references to the actual QListWidgetItems that are being dragged in the event's QMimeData. This would allow me to do the deletions by hand, before I trigger updates.
Figure out how to wait until the source has been automatically cleared, but I can't find any signals that fire when items are removed from a list automatically.
Aha!
The key I was missing was the mimeData method. This method is called when a drag is started, and in it I am passed a list of all files being dragged.
I first built the meta object to be returned, then I deleted the files being dragged from the list, and called the refresh action that I needed.
Here's an example:
def mimeData(self, items):
m = QMimeData()
m.setUrls([QUrl(i.url) for i in items])
# Clean up the list:
[self.files.takeItem(self.files.indexFromItem(i).row()) for i in items]
self._update_meta()
return m
Related
I may have worked myself into a corner but this sounded to me like a good idea at the time.
I have been developing an interface that permits a user to modify settings of a robotic device, i.e. speed, directions, force, etc. with a very large series of options in the form of ComboBoxes. The problem is that there are about a thousand of these things, in sub categories. e.g. Speed category x1, x2, x3, Y1, y2, etc. So rather than create a thousand comboboxes in QT, I thought the good idea was to create one set of 50 (ish) and then provide a few button to switch between categories. So when the user selects speed QT, populates the comboboxes with the appropriate options, sets the style sheets and text for the labels etc. So it appears as though a dedicated page exists. Then if the user selects Direction, QT Writes the current index of each box to a dedicated array and then repopulates the boxes, labels etc with the appropriate content. I then do this over and over for the various needs of the system.
All of that seems to work fine. However I am now in a bind where the options provided to navigate to each page have grown. For instance I have forward / backward buttons (like you woudl expect in a set-up wizard), as well as action menus at the top to jump to a page. So now the code is becoming very repetitious. If you select the next button, I write the current values to array, then repopulate. If you jump to the page from anywhere, I look to see where I am, write it to array, and populate the boxes. Thus if I need to change anything I have to make the change in numerous places in the code.
I know that this is not optimal. What I woudl like to do is run a continuous loop as I woudl normally do with Micros in C. So the program can look at a variable in each pass and if it is then it does. I am not however skilled enough to figure this loop out in QT. So my new thought was...
Is it possible to trigger an action or slot with a variable. For example, if the user presses the Next button it triggers a slot for a button that does not exist, so that QT will execute a particular line of Code? Then I can have 1 dedicated section focused on reading and writing boxes, with a bunch of actions that will take me there.
You can make a signal that is triggered with an emit call in your code, so you'd hook up the next button signal of clicked to a slot that does some work and moves on, or directly calls another signal that you've created that triggers a slot elsewhere, or do some work in a lambda triggered by the button press.
I would first load all the ComboBoxes options in a QStringList array (or maybe an array of QList<QLatin1String> lists - for memory saving and code efficiency).
Then I would keep an array of a 1000 integers for current ComboBox indexes.
When the user changes a value in some ComboBox, the currentIndexChanged signal will trigger the corresponding slot (a single slot for all the ComboBoxes would be enough - sender()->objectName() to get the name of the ComboBox which had sent the signal):
void WindowWidget::on_ComboBox_currentIndexChanged(int index)
{
name = sender()->objectName();
/* here change the corresponding integer in the current
indexes array */
}
On Next/Back button push repopulate the ComboBoxes. Also, provide some 'Save' button for saving the ComboBoxes indexes (or trigger the Save slot on some action, i.e. on window close either even on a timer signal).
There is a dictionary taken from JSON file, that is represented by QTreeView QStandardItemModel.
A user can reorganize QTreeView(add, delete, drag-n-drop) and rename items.
The goal is: call function that reads changed QTreeView, makes the dictionary and writes it to initial JSON file.
I can do it by pressing a QPushButton after changes occurred or by binding that function to every change e.g. call function when an item is deleted, call function when an item is added, call a function when an item is renamed and so on.
Is there any way to call a function if any of changes occur? Is there such a signal that corresponds to all of the mentioned changes?
The rowsMoved and itemChanged signals do what you think they do. See http://doc.qt.io/qt-4.8/qstandarditemmodel.html
As #vahancho suggests in the comments, you should connect to the layoutChanged signal. All models should emit this immedaitely after making any changes which could affect the view. So this will include sorting and filtering, as well as re-ordering, editing, deleting, etc.
The dataChanged signal is similar, but only really useful if you want to monitor specific items.
How can I refresh view after a certain event?
I have a view which contains multiple groups. I want to show or hide some groups.
onCreationComplete() or initialize() method works only at the beginning of the view creation.
Try invalidateDisplayList() on the view
Let me know if that doesn't do the trick and we'll try some other tricks.
I personally don't like the answer that says to call invalidateDisplayList (sorry no offense Nate nothing personal). I feel it's too vague and doesn't explain what this does under the hood and furthermore you shouldn't have to call it directly in cases such as the one explained in the OPs question. You can simply create booleans that are bindable for each of the groups you'd like to show/hide then in the event handler set those booleans to the appropriate value and if they are bound to the visible and include in layout properties of the containers those containers will internally call invalidateDisplayList after calling set visible and consequently commitProperties.
This is basically what happens under the hood as I understand it: The way this works is values aren't committed or used to update the display until the next frame this way it doesn't get bogged down doing unnecessary layout calculations. So you update the bindable property which fires an event which triggers a notification in the listener (in this case a function that sets the property on your control), that in turn passes along the value to the control which sets an internal flag to update the property and calls invalidateProperties. When it hits the next frame redraw it sees that the properties flag is dirty (true) and then calls commitProperties, this computes/sets the appropriate values (possibly also invalidating then "fixing" the size using invalidateSize() and measure()) and calls invalidateDisplayList, then during the same frame it sees that the display list flag is dirty so it calls updateDisplayList, here it uses the values of the properties to draw appropriately.
You should also be able to achieve this using states, which add or remove children from the display list based on an array of "actions" for each state.
I am using PyQt4, but this is general enough that it could just apply to QT.
I have a series of QComboBoxes that I fill from left to right (i.e. selecting an item in the leftmost will populate the next one. Selecting an item in that one will populate the next, and so on)
I am having difficulty getting my signals to fire under all situations (i.e. regardless of whether the current index changes or not AND regardless of whether the item is set by the user or set programatically).
More detail:
I rely on the signals of the first QCombox to fire whenever an item is selected so that I can populate the next QCombobox in the gui. I then rely on THAT QCombobox to emit a signal so that I can populate the next one. And so on.
I want to pre-select an item in each QCombobox based on the user's last interaction with the gui.
I have a unique function per QCombobox that is responsible for populating and pre-selecting just that QCombobox. The code looks something like this:
comboBox1.blockSignals(True)
comboBox1.clear()
comboBox1.addItems(sorted(itemList))
comboBox1.blockSignals(False)
comboBox1.setCurrentIndex(intLastSavedState1)
where intLastSavedState1 is an integer that is derived from the text that was last selected by the user the last time they had used the app. I had hoped that the last line of this function would fire a signal that would cause the next combo box's function to load and pre-select an item (comboBox2). And that action would then cause the next comboBox's function to activate and it would cascade to the next and the next. But it is not working across all cases.
I have tried two versions of the signals:
self.connect(comboBox1, QtCore.SIGNAL("currentIndexChanged(const QString&)"), self.load_comboBox2)
and
self.connect(comboBox1, QtCore.SIGNAL("activated(const QString&)"), self.load_comboBox2)
In the first case, the signal will fire only if the intLastSavedState1 is different than whatever is currently selected in the combo box. This causes an issue if the user had last selected item 0 from that list. In this case QT does not recognize my script setting the the current index to 0 as being a change (since after loading the box it appears to think it is already on index 0), and so the signal does not fire.
In the second case, the signal will fire regardless of what is currently selected in the combo box... but only if activated by the user. It will not fire when my script tries to set the current index programatically.
These appear to be my only two options regarding the signals. So... is there another way of pre-selecting items in a QCombobox that will trigger a signal each and every time?
Well... sometimes just the act of asking a question can lead you to a (partial) answer.
I have a work-around but I am still interested in hearing if someone has a better idea.
I am now programatically setting the index of the QCombobox to -1 immediately after loading it up. Then, when I programatically set the actual index based on the user's history, it will always be considered a change (i.e. it will never be -1) and the signal will fire
using: currentIndexChanged(const QString&)
So my code looks like this now:
comboBox1.blockSignals(True)
comboBox1.clear()
comboBox1.addItems(sorted(itemList))
comboBox1.setCurrentIndex(-1)
comboBox1.blockSignals(False)
comboBox1.setCurrentIndex(intLastSavedState1)
and my signal looks like this:
self.connect(comboBox1, QtCore.SIGNAL("currentIndexChanged(const QString&)"), self.load_comboBox2)
This functions... does anyone have a better idea?
Thanks agian.
You can check current Index of your ComboBox and then either call your slot or do call setCurrentIndex().
Example:
if comboBox1.currentIndex() == index:
self.load_comboBox2(index)
else
comboBox1.setCurrentIndex(index)
This way you will not end up calling slot twice.
How can I autocommit data from QTableWidget, that is in editing state, when I fire some command?
Assume, that there is some grid and data in it (editable thorough delegate that fires QComboBox editor). So, one starting to select option in combo, but do not finish editing, then hit some button, that executes action, that uses data from that combo, but new choise is not committed yet :\
How can I programmatically finish editing in table?
I mean some not strict 'loop all items and finish editing' way, that I consider as bad and ugly.
OOPS: worked too much, so, haven't realised, that there could be only one pending editor at time. Question is still here.
There is a protected slot named "commitData" in the tableWidget. You can inherit from tableWidget, then add your own public method (or slot) and send a signal (or simply call commitData method) from there.
There is one problem. You'll need to provide the editor object, but tableWidget gives you no way to get the pointer you need.
If you're using your own createEditor method, you can save the pointer to the editor somewhere, where your method can get it. It's a hack, but it's the only way i know.
The current editor does not seem to be accessible from outside of the view, but its content is committed when the current model index changes. So a simple way to force a commit seems to be to call
table->setCurrentIndex (QModelIndex ())
plus restoring your previous current index afterwards if the widget is not discarded yet.
This is quite an old question but it still came up quite high on Google so just in case anyone else needs the answer QTableView has a protected method
void currentChanged(const QModelIndex ¤t, const QModelIndex &previous)
which causes the data to be commited and QTableWidget is built on QTableView so that should still work. I found this info on the Qt Forum.