带有上下文菜单的 QTreeWidget，无法获取正确的项目

Question

I have the following code to create a QTreeWidget and a contextmenu with 2 actions.

import sys
from PyQt5 import QtCore, QtWidgets

class Dialog(QtWidgets.QDialog):
    def __init__(self, parent=None):
        super(Dialog, self).__init__()

        self.tw = QtWidgets.QTreeWidget()
        self.tw.setHeaderLabels(['Name', 'Cost ($)'])
        cg = QtWidgets.QTreeWidgetItem(['carrots', '0.99'])
        c1 = QtWidgets.QTreeWidgetItem(['carrot', '0.33'])
        self.tw.addTopLevelItem(cg)
        self.tw.addTopLevelItem(c1)
        self.tw.installEventFilter(self)
        layout = QtWidgets.QVBoxLayout(self)
        layout.addWidget(self.tw)

    def eventFilter(self, source: QtWidgets.QTreeWidget, event):
        if (event.type() == QtCore.QEvent.ContextMenu and
            source is self.tw):
            menu = QtWidgets.QMenu()
            AAction = QtWidgets.QAction("AAAAA")
            AAction.triggered.connect(lambda :self.a(source.itemAt(event.pos())))
            BAction = QtWidgets.QAction("BBBBBB")
            BAction.triggered.connect(lambda :self.b(source, event))
            menu.addAction(AAction)
            menu.addAction(BAction)
            menu.exec_(event.globalPos())
            return True
        return super(Dialog, self).eventFilter(source, event)

    def a(self, item):
        if item is None:
            return
        print("A: {}".format([item.text(i) for i in range(self.tw.columnCount())]))
    def b(self, source, event):
        item = source.itemAt(event.pos())
        if item is None:
            return
        print("B: {}".format([item.text(i) for i in range(source.columnCount())]))

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    window = Dialog()
    window.setGeometry(600, 100, 300, 200)
    window.show()
    sys.exit(app.exec_())

When opening the contextmenu in the header and clicking on one of the actions it prints either carrot or carrots, depending on where in the contextmenu I click. But I give the position of right click event to the functions.

So why is this happening and what can I do to stop it?

Answer 1

Your code has 2 errors:

• The main error is that the itemAt() method uses the coordinates with respect to the viewport() and not with respect to the view (the QTreeWidget) so you will get incorrect items (the header occupies a space making the positions with respect to the QTreeWidget and the viewport() have an offset).

• You should not block the eventloop, for example blocking the eventFilter you may be blocking other events that would cause errors that are difficult to debug, in this case it is better to use a signal.

class Dialog(QtWidgets.QDialog):
    rightClicked = QtCore.pyqtSignal(QtCore.QPoint)

    def __init__(self, parent=None):
        super(Dialog, self).__init__()

        self.tw = QtWidgets.QTreeWidget()
        self.tw.setHeaderLabels(["Name", "Cost ($)"])
        cg = QtWidgets.QTreeWidgetItem(["carrots", "0.99"])
        c1 = QtWidgets.QTreeWidgetItem(["carrot", "0.33"])
        self.tw.addTopLevelItem(cg)
        self.tw.addTopLevelItem(c1)

        self.tw.viewport().installEventFilter(self)

        layout = QtWidgets.QVBoxLayout(self)
        layout.addWidget(self.tw)

        self.rightClicked.connect(self.handle_rightClicked)

    def eventFilter(self, source: QtWidgets.QTreeWidget, event):
        if event.type() == QtCore.QEvent.ContextMenu and source is self.tw.viewport():
            self.rightClicked.emit(event.pos())
            return True

        return super(Dialog, self).eventFilter(source, event)

    def handle_rightClicked(self, pos):
        item = self.tw.itemAt(pos)
        if item is None:
            return
        menu = QtWidgets.QMenu()
        print_action = QtWidgets.QAction("Print")
        print_action.triggered.connect(lambda checked, item=item: self.print_item(item))
        menu.addAction(print_action)
        menu.exec_(self.tw.viewport().mapToGlobal(pos))

    def print_item(self, item):
        if item is None:
            return
        texts = []
        for i in range(item.columnCount()):
            text = item.text(i)
            texts.append(text)

        print("B: {}".format(",".join(texts)))

Although it is unnecessary that you use an eventFilter to handle the contextmenu since a simpler solution is to set the contextMenuPolicy of the QTreeWidget to Qt::CustomContextMenu and use the customContextMenuRequested signal:

class Dialog(QtWidgets.QDialog):
    def __init__(self, parent=None):
        super(Dialog, self).__init__()

        self.tw = QtWidgets.QTreeWidget()
        self.tw.setHeaderLabels(["Name", "Cost ($)"])
        cg = QtWidgets.QTreeWidgetItem(["carrots", "0.99"])
        c1 = QtWidgets.QTreeWidgetItem(["carrot", "0.33"])
        self.tw.addTopLevelItem(cg)
        self.tw.addTopLevelItem(c1)

        self.tw.setContextMenuPolicy(QtCore.Qt.CustomContextMenu)
        self.tw.customContextMenuRequested.connect(self.handle_rightClicked)

        layout = QtWidgets.QVBoxLayout(self)
        layout.addWidget(self.tw)

    def handle_rightClicked(self, pos):
        item = self.tw.itemAt(pos)
        if item is None:
            return
        menu = QtWidgets.QMenu()
        print_action = QtWidgets.QAction("Print")
        print_action.triggered.connect(lambda checked, item=item: self.print_item(item))
        menu.addAction(print_action)
        menu.exec_(self.tw.viewport().mapToGlobal(pos))

    def print_item(self, item):
        if item is None:
            return
        texts = []
        for i in range(item.columnCount()):
            text = item.text(i)
            texts.append(text)

        print("B: {}".format(",".join(texts)))