如何在 PyQt 中的自定义 Qt.ItemFlags 实例中找到特定的 Qt.ItemFlag 出现？

我有一个QTreeWidget http://www.riverbankcomputing.com/static/Docs/PyQt4/html/qtreewidget.html with QTreeWidgetItem http://www.riverbankcomputing.com/static/Docs/PyQt4/html/qtreewidgetitem.html。方法QTreeWidgetItem.flags() http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qtreewidgetitem.html#flags返回我Qt.ItemFlags http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qt-itemflags.html实例。

The Qt.ItemFlags http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qt-itemflags.htmltype 是 QFlags 的类型定义。它存储一个 OR 组合ItemFlag http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qt.html#ItemFlag-enum values.

好吧，假设现在我有我的一个QTreeWidgetItem http://www.riverbankcomputing.com/static/Docs/PyQt4/html/qtreewidgetitem.html我需要弄清楚——它是否可以检查？换句话说，我需要找到出现的情况ItemFlag http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qt.html#ItemFlag-enum（就我而言，它是Qt.ItemIsUserCheckable http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qt.html#ItemFlag-enum) in Qt.ItemFlags http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qt-itemflags.html实例。

怎么做？

这是一个简单而整洁的示例，您可以修改（感兴趣的部分由注释行标记）：

import sys
from PyQt4 import QtCore, QtGui

class Window(QtGui.QWidget):

    def __init__(self):
        QtGui.QWidget.__init__(self)
        self.treeWidget = QtGui.QTreeWidget()
        self.treeWidget.setHeaderHidden(True)
        self.addItems(self.treeWidget.invisibleRootItem())
        self.treeWidget.itemClicked.connect (self.handleClicked)
        layout = QtGui.QVBoxLayout()
        layout.addWidget(self.treeWidget)
        self.setLayout(layout)

    def addItems(self, parent):
        column = 0

        clients_item = QtGui.QTreeWidgetItem(parent, ['Clients'])
        clients_item.setData(column, QtCore.Qt.UserRole, 'data Clients')
        clients_item.setExpanded(True)

        item_1 = QtGui.QTreeWidgetItem(clients_item, ['Item 1'])
        item_1.setData(column, QtCore.Qt.UserRole, 'data Item 1')
        item_1.setCheckState(column, QtCore.Qt.Unchecked)

        item_2 = QtGui.QTreeWidgetItem(clients_item, ['Item 2'])
        item_2.setData(column, QtCore.Qt.UserRole, 'data Item 2')
        item_2.setCheckState(column, QtCore.Qt.Unchecked)

    def handleClicked(self, item, column):
        if item.checkState(column) == QtCore.Qt.Checked:
            print "checked", item, item.text(column)
        if item.checkState(column) == QtCore.Qt.Unchecked:
            print "NOT checked", item, item.text(column)

        # this part doesn't work ===============================
        # begin of part
        flags = item.flags()
        if QtCore.Qt.ItemIsUserCheckable in flags:
            print "is checkable", item, item.text(column)
        else:
            print "is NOT checkable", item, item.text(column)
        # end of part ==========================================    

if __name__ == "__main__":

    app = QtGui.QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())

与 Qt 中的许多“标志”和“属性”一样，ItemFlags使用位掩码将多个选项组合成一个值。这可以使用按位运算符进行测试。

以下是检查该项目是否可检查的方法：

flags = item.flags()
if flags & QtCore.Qt.ItemIsUserCheckable:
    print "is checkable", item, item.text(column)

按位掩码 http://en.wikipedia.org/wiki/Mask_%28computing%29

它的工作原理如下：

Qt.NoItemFlags          0   It does not have any properties set.
Qt.ItemIsSelectable     1   It can be selected.
Qt.ItemIsEditable       2   It can be edited.
Qt.ItemIsDragEnabled    4   It can be dragged.
Qt.ItemIsDropEnabled    8   It can be used as a drop target.
Qt.ItemIsUserCheckable  16  It can be checked or unchecked by the user.
Qt.ItemIsEnabled        32  The user can interact with the item.
Qt.ItemIsTristate       64  The item is checkable with three separate states.

所以该值将是这些值的某种组合。可以说它是可选择的、可编辑的并且已启用。为简单起见，我将仅使用数值而不是标志。我们用逻辑或将它们组合起来：

flags = 1 | 2 | 32
# 35

为了测试某个值是否存在，我们使用逻辑 AND：

# is it editable?
flags & 2
# 2 # would evaluate to True

# is it checkable?
flags & 16
# 0 # would evaluate to False

您还可以使用 XOR 运算来切换标记中的标志状态。

# toggle off the editable flag
flags ^= 2
# toggle on the editable flag
flags ^= 2