How to implement itemChecked and itemUnchecked signals for QTreeWidget in PyQt4?

Question

Where are the signals itemChecked and itemUncheсked on the QTreeWidget?

Qt Signals: (quote from PyQt4 QTreeWidget documentation page)

void currentItemChange         


        

Answer 1

To complete the answer of @ekhumoro, and to give a shorter answer (without subclassing QTreeWidgetItem): block the signal :

self.treeWidget.blockSignals(True)
self.treeWidget.blockSignals(False)

and use

self.treeWidget.itemChanged

to connect to what you want. the signal is used when the data is changed (text inside, checked state, ...) and in your function linked to this signal verify if the treeWidget has changed is checked state.

Answer 2

To avoid problems with recursion when using the itemChanged signal, try temporarily blocking signals until the handler has completed:

def handle(self, item, column):
    self.treeWidget.blockSignals(True)
    if item.checkState(column) == QtCore.Qt.Checked:
        self.handleChecked(item, column)
    elif item.checkState(column) == QtCore.Qt.Unchecked:
        self.handleUnchecked(item, column)
    self.treeWidget.blockSignals(False)

UPDATE

The other part of your question asked about emitting a signal only when an item is checked.

One way to do this would be to subclass QTreeWidgetItem and reimplement it's setData function:

class TreeWidgetItem(QtGui.QTreeWidgetItem):
    def setData(self, column, role, value):
        state = self.checkState(column)
        QtGui.QTreeWidgetItem.setData(self, column, role, value)
        if (role == QtCore.Qt.CheckStateRole and
            state != self.checkState(column)):
            treewidget = self.treeWidget()
            if treewidget is not None:
                treewidget.itemChecked.emit(self, column)

class Window(QtGui.QTreeWidget):
    itemChecked = QtCore.pyqtSignal(object, int)

    def __init__(self, rows, columns):
        QtGui.QTreeWidget.__init__(self)
        self.itemChecked.connect(self.handleItemChecked)

    def handleItemChecked(self, item, column):
        print 'ItemChecked', int(item.checkState(column))