CODEWITHSUNDEEP
pythonqtcrashpyqtqtreewidget
oldPadavan
oldPadavan

Reputation: 300

PyQt QTreeWidget.clear() causes crash

I've got python 2.5 and PyQt 4.8.6 installed. Os - Windows Xp Sp2. I use the following code to fill TreeWidget:

def updateTreeWidget(self, widget, results):
        """ Updates the widget with given results """
        widget.clear()
        for item in results:
            temp = QtGui.QTreeWidgetItem()
            j = 0
            for elem in item: 
                temp.setText(j , str(elem))
                j += 1
            widget.addTopLevelItem(temp)       
        for column in range(widget.columnCount()):
            widget.resizeColumnToContents(column)

It causes crashes at the second use of it. If I comment out one of the following lines:

widget.addTopLevelItem(temp)

or 

widget.clear()

it works without problems.

I call the function in the thread every 60s. Here is the definition of MyThread class.

class MyThread(threading.Thread):
    def __init__(self, db, widget, function, script, parameter):
        threading.Thread.__init__(self)
        self.db = db
        self.function = function
        self.script = script
        self.parameter = parameter
        self.widget = widget
        self.event = threading.Event()

    def run(self):            
        while 1:
            self.event.wait(60)
            parameter = [getCurrentTimeStr()] + self.parameter
            res = self.db.getQuery(self.script % tuple(parameter))
            self.function(self.widget, res)

This thread is started when in main window init():

class MainWnd(QtGui.QMainWindow):
    def __init__(self, parent = None):

        # some code

        self.db = DbAccess()

        QtGui.QWidget.__init__(self, parent)

        self.ui = Ui_mainWnd()
        self.ui.setupUi(self)

        self.thread = MyThread(self.db, self.ui.treeWidget, self.updateTreeWidget, self.script, self.param)
        self.thread.start()

The widget was created using Qt Designer.

Upvotes: 6

Views: 5423

Answers (1)

Chris
Chris

Reputation: 17535

Updating GUI elements from a thread that is not the same as Qt's event loop is a big no-no.

The customary way to solve this is to used a queued signal/slot connection or a singleshot QTimer to pass thread boundaries and execute your function on the main thread.

Upvotes: 3

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