PyQt5突出显示选定的TreeWidget单元格

我的树表使用浮点，我想限制表中显示的小数位数，但我不想丢失数据，因为我用它执行计算。我ItemDelegate对paint方法进行了子类化和覆盖，这样我就可以在单元格中绘制更少的小数点而不会实际丢失数据。这个代码如下，主要关注的是try块的最后一行。

def paint(self, painter, option, index):

value = index.model().data(index, QtCore.Qt.EditRole)
item = self.treeWidget.itemFromIndex(index)
col = index.column()

try:
    if col == 0:
        QtWidgets.QItemDelegate.paint(self, painter, option, index)

    else:

        if isinstance(item, AssignmentType):
            painter.setPen(QtCore.Qt.darkGreen)
            painter.setFont(typeFont)

        elif isinstance(item, Assignment):
            painter.setPen(QtCore.Qt.blue)
            painter.setFont(assFont)
        else:
            painter.setPen(QtCore.Qt.darkBlue)
            painter.setFont(courseFont)

        text = value if "/" in value else "{:.{}f}".format(float(value)*100, self.nDecimals)
        painter.drawText(option.rect, QtCore.Qt.AlignCenter, text)

except:
    QtWidgets.QItemDelegate.paint(self, painter, option, index)

这样做的副作用是，painter.drawText(option.rect, QtCore.Qt.AlignCenter, text)单击代码行时受到影响的单元格不会突出显示。我已经尝试在我的paint方法中有条件地更改树小部件的调色板，但这似乎没有帮助。我认为连接itemClicked信号会有所帮助，但我不知道我会在那里做什么。该项目的完整代码和示例.grdb文件如下：

import json

from PyQt5 import QtCore, QtGui, QtWidgets

courseFont = QtGui.QFont()
courseFont.setBold(True)
courseFont.setWeight(100)
courseFont.setPointSize(18)

typeFont = QtGui.QFont()
typeFont.setUnderline(True)
typeFont.setPointSize(16)
typeFont.setWeight(50)

assFont = QtGui.QFont()
assFont.setItalic(True)
assFont.setPointSize(14)
assFont.setWeight(50)

extraCreditFont = QtGui.QFont()
extraCreditFont.setItalic(True)
extraCreditFont.setUnderline(True)
extraCreditFont.setPointSize(14)
extraCreditFont.setWeight(75)

class KeyPressedTree(QtWidgets.QTreeWidget):

keyPressed = QtCore.pyqtSignal(int)

def keyPressEvent(self, event):
    super(KeyPressedTree, self).keyPressEvent(event)
    self.keyPressed.emit(event.key())

class Course(QtWidgets.QTreeWidgetItem):

def __init__(self, parent, data=["New Course", "", ""], *__args):
    super().__init__(parent, data)
    self.setFont(0, courseFont)
    self.setFlags(
        QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsEditable | QtCore.Qt.ItemIsDragEnabled | QtCore.Qt.ItemIsUserCheckable | QtCore.Qt.ItemIsEnabled)

class AssignmentType(QtWidgets.QTreeWidgetItem):

def __init__(self, parent, data=["New Assignment Type", "", ""], *__args):
    super().__init__(parent, data)
    self.setFont(0, typeFont)
    self.setFlags(
        QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsEditable | QtCore.Qt.ItemIsDragEnabled | QtCore.Qt.ItemIsUserCheckable | QtCore.Qt.ItemIsEnabled)

    self.extraCredit = False

def setExtraCredit(self,isExtra):
    self.extraCredit = isExtra
def isExtraCredit(self):
    return self.extraCredit

class Assignment(QtWidgets.QTreeWidgetItem):

def __init__(self, parent, data=["New Assignment", "", ""], *__args):
    super().__init__(parent, data)
    self.setFont(0, assFont)
    self.extraCredit = False
    self.setFlags(
        QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsEditable | QtCore.Qt.ItemIsDragEnabled | QtCore.Qt.ItemIsUserCheckable | QtCore.Qt.ItemIsEnabled)

def setExtraCredit(self,isExtra):
    self.extraCredit = isExtra
def isExtraCredit(self):
    return self.extraCredit

class ValidWeightGradeInput(QtWidgets.QItemDelegate):

def createEditor(self, parent, option, index):
    line = QtWidgets.QLineEdit(parent)
    reg_ex = QtCore.QRegExp(r"|0?\.\d+|\d*\.?\d+/\d*\.?\d+")
    input_validator = QtGui.QRegExpValidator(reg_ex, line)
    line.setValidator(input_validator)
    return line

class FloatDelegate(QtWidgets.QItemDelegate):

def __init__(self, decimals, parent: KeyPressedTree):
    self.treeWidget = parent
    QtWidgets.QItemDelegate.__init__(self, parent=parent)
    self.nDecimals = decimals

def createEditor(self, parent, option, index):
    # if any of the below conditions are met, then the cell is editable.
    # basically, if the first index is zero, then it's editable
    # if the weight column for the assignment type item is selected, then it's editable
    # if the grade column for the assignment item is selected, it's editable
    # in all other cases, it's not editable.
    if index.column() == 0:
        return QtWidgets.QItemDelegate.createEditor(self, parent, option, index)
    elif (
            index.column() == 1 and isinstance(self.treeWidget.itemFromIndex(index), AssignmentType)) or (
            index.column() == 2 and isinstance(self.treeWidget.itemFromIndex(index), Assignment)):

        return ValidWeightGradeInput.createEditor(self, parent, option, index)

    else:
        return None

def paint(self, painter, option, index):
    value = index.model().data(index, QtCore.Qt.EditRole)
    item = self.treeWidget.itemFromIndex(index)
    col = index.column()

    try:
        if col == 0:
            QtWidgets.QItemDelegate.paint(self, painter, option, index)

        else:

            if isinstance(item, AssignmentType):
                painter.setPen(QtCore.Qt.darkGreen)
                painter.setFont(typeFont)

            elif isinstance(item, Assignment):
                painter.setPen(QtCore.Qt.blue)
                painter.setFont(assFont)
            else:
                painter.setPen(QtCore.Qt.darkBlue)
                painter.setFont(courseFont)

            text = value if "/" in value else "{:.{}f}".format(float(value)*100, self.nDecimals)
            painter.drawText(option.rect, QtCore.Qt.AlignCenter, text)

    except:
        QtWidgets.QItemDelegate.paint(self, painter, option, index)

class Ui_MainWindow(QtWidgets.QMainWindow):

def setupUi(self):
    self.setWindowTitle("Grade Manager")
    self.resize(620, 600)
    self.centralwidget = QtWidgets.QWidget(self)
    self.verticalLayout = QtWidgets.QVBoxLayout(self.centralwidget)
    self.treeWidget = KeyPressedTree(self.centralwidget)
    sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
    sizePolicy.setHeightForWidth(self.treeWidget.sizePolicy().hasHeightForWidth())
    self.treeWidget.setSizePolicy(sizePolicy)
    self.treeWidget.setMinimumSize(QtCore.QSize(620, 600))

    font = QtGui.QFont()
    font.setPointSize(20)
    font.setWeight(100)
    self.treeWidget.setFont(font)

    self.treeWidget.setAlternatingRowColors(True)
    self.treeWidget.setSelectionBehavior(QtWidgets.QAbstractItemView.SelectItems)
    self.treeWidget.setAnimated(True)
    self.treeWidget.setWordWrap(True)

    self.treeWidget.headerItem().setText(0, "Course")
    self.treeWidget.headerItem().setText(1, "Weight")
    self.treeWidget.headerItem().setText(2, "Grade")
    self.treeWidget.headerItem().setTextAlignment(0, QtCore.Qt.AlignCenter)
    self.treeWidget.headerItem().setTextAlignment(1, QtCore.Qt.AlignCenter)
    self.treeWidget.headerItem().setTextAlignment(2, QtCore.Qt.AlignCenter)

    self.treeWidget.setColumnWidth(0,370)
    self.treeWidget.setColumnWidth(1,130)
    self.treeWidget.setColumnWidth(2,100)
    # self.treeWidget.header().setDefaultSectionSize(275)
    # self.treeWidget.header().setMinimumSectionSize(50)
    self.treeWidget.header().setStretchLastSection(True)

    self.verticalLayout.addWidget(self.treeWidget)
    self.setCentralWidget(self.centralwidget)
    self.menubar = QtWidgets.QMenuBar(self)
    self.menubar.setGeometry(QtCore.QRect(0, 0, 912, 35))

    self.menuFile = QtWidgets.QMenu(self.menubar)
    self.menuFile.setTitle("Fi&le")

    self.setMenuBar(self.menubar)
    self.actionOpen = QtWidgets.QAction(self, text="&Open")
    self.actionOpen.setShortcut("Ctrl+O")
    self.actionClose = QtWidgets.QAction(self, text="&Close")
    self.actionNew = QtWidgets.QAction(self, text="&New")
    self.actionSave = QtWidgets.QAction(self, text="&Save")
    self.actionSave.setShortcut("Ctrl+S")
    self.actionSave_as = QtWidgets.QAction(self, text="Sa&ve as...")
    self.actionSave_as.setShortcut("Ctrl+Shift+S")

    self.menuFile.addAction(self.actionNew)
    self.menuFile.addAction(self.actionOpen)
    self.menuFile.addAction(self.actionClose)
    self.menuFile.addSeparator()
    self.menuFile.addAction(self.actionSave)
    self.menuFile.addAction(self.actionSave_as)
    self.menubar.addAction(self.menuFile.menuAction())

    self.courses = []
    self.treeWidget.setItemDelegate(FloatDelegate(2, self.treeWidget))

    self.treeWidget.setContextMenuPolicy(QtCore.Qt.CustomContextMenu)

    self.treeWidget.customContextMenuRequested.connect(self.openMenu)

    self.actionSave.triggered.connect(self.saveJSON)
    self.actionOpen.triggered.connect(self.readJSON)
    self.actionSave_as.triggered.connect(self.saveAsJSON)
    self.actionNew.triggered.connect(self.clearPage)
    self.actionClose.triggered.connect(self.close)

    self.treeWidget.itemChanged.connect(self.itemClicked)
    self.treeWidget.keyPressed.connect(self.keyPressed)

    self.filename = None
    self.change_made = False

def clearPage(self):
    if self.change_made:
        answer = QtWidgets.QMessageBox.question(self, "Close Confirmation",
                                                "Would you like to save before exiting?",
                                                QtWidgets.QMessageBox.Yes | QtWidgets.QMessageBox.No | QtWidgets.QMessageBox.Cancel)

        if answer == QtWidgets.QMessageBox.Cancel:
            return
        elif answer == QtWidgets.QMessageBox.Yes:
            self.saveJSON()
    self.treeWidget.clear()
    self.courses = []
    self.filename = None
    self.change_made = False

def addCourse(self):
    course = Course(self.treeWidget)
    course.setExpanded(True)
    self.courses.append(course)
    self.change_made = True

def addType(self, course):
    t = AssignmentType(course)
    t.setExpanded(True)
    course.addChild(t)
    self.change_made = True

def addAssignment(self, assignment_type):
    ass = Assignment(assignment_type)
    assignment_type.addChild(ass)
    self.change_made = True

def removeItem(self, item, level):
    root = self.treeWidget.invisibleRootItem()
    parent = item.parent()
    (parent or root).removeChild(item)

    if level == 2:  # if just the assignment was removed
        self.updateTypeGrade(parent)
    elif level == 1:  # if the assignment type was just removed
        self.updateCourseGrade(parent)
    self.change_made = True

def openMenu(self, position):
    menu = QtWidgets.QMenu(self)
    indices = self.treeWidget.selectedItems()

    level = 0
    if not indices:
        menu.addAction(self.tr("Add New Course"))

    else:
        i = indices[0]
        while i.parent():
            i = i.parent()
            level += 1
        choices = (("Add New Course", "Add New Assignment Type", "Remove Selected Course"),
                   ("Add New Assignment", "Remove Selected Assignment Type"), ("Remove Assignment",
                                                                               "Set As Not Extra Credit" if level == 2 and indices[0].isExtraCredit() else "Set As Extra Credit"))

        [menu.addAction(self.tr(act)) for act in choices[level]]

    action = menu.exec_(self.treeWidget.viewport().mapToGlobal(position))
    if action:
        action = action.text()
        if action == "Add New Course":
            self.addCourse()
        elif action == "Add New Assignment Type":
            self.addType(indices[0])
        elif action == "Add New Assignment":
            self.addAssignment(indices[0])
        elif action == "Set As Extra Credit":
            indices[0].setExtraCredit(True)
            self.updateTypeGrade(indices[0].parent())
            indices[0].setFont(0,extraCreditFont)
            self.change_made = True
        elif action == "Set As Not Extra Credit":
            indices[0].setExtraCredit(False)
            self.updateTypeGrade(indices[0].parent())
            indices[0].setFont(0,assFont)
            self.change_made = True
        else:
            self.removeItem(indices[0], level)

def saveJSON(self):
    self.filename = self.save(self.filename)

def saveAsJSON(self):
    self.save()

def transformInput(self, data: str):
    if "/" in data:
        i = data.find("/")
        return float(data[:i]) / float(data[i + 1:])
    return float(data)

def updateTypeGrade(self, ass_type):
    type_grade = 0.0
    num_assignments = ass_type.childCount()
    for i in range(num_assignments):
        grade = ass_type.child(i).text(2)
        if not grade:  # if the column is empty
            num_assignments -= 1
            continue
        if ass_type.child(i).isExtraCredit():
            num_assignments -= 1
        type_grade += self.transformInput(grade)
    type_grade = f"{type_grade / num_assignments}" if num_assignments > 0 else ""
    ass_type.setText(2, type_grade)

def updateCourseGrade(self, course):
    total_weight = 0.0
    earned_weight = 0.0
    for i in range(course.childCount()):
        t = course.child(i)
        weight = t.text(1)
        grade = t.text(2)
        if not weight or not grade:  # if no weight is entered
            continue
        total_weight += self.transformInput(weight)
        earned_weight += self.transformInput(weight) * self.transformInput(grade)
    course_grade = str(earned_weight / total_weight) if total_weight > 0 else ""
    course.setText(2, course_grade)

def itemClicked(self, item, col):
    self.change_made = True
    if isinstance(item, Course) or col == 0:
        return
    elif isinstance(item, Assignment):
        item = item.parent()  # changes assignment to the assignment type
        self.updateTypeGrade(item)
    # from this point, the item must be an assignment type.
    self.updateCourseGrade(item.parent())

def keyPressed(self, key):
    indices = self.treeWidget.selectedItems()

    level = 0
    if not indices:  # if no tree item is selected
        if key == QtCore.Qt.Key_Insert:
            self.addCourse()
    else:
        i = indices[0]
        while i.parent():
            i = i.parent()
            level += 1
        i = indices[0]
        if key == QtCore.Qt.Key_Delete:
            self.removeItem(i, level)

        else:
            if level == 0:
                if key == QtCore.Qt.Key_Insert:
                    self.addType(i)
            elif level == 1:
                if key == QtCore.Qt.Key_Insert:
                    self.addAssignment(i)
            elif level == 2:
                pass

def save(self, filename=None):
    if not filename:  # if a file hasn't been opened yet (save as or new file)
        filename, _ = QtWidgets.QFileDialog.getSaveFileName(self, "Save File", "./",
                                                            "Gradebook Files (*.grdb)")
    if filename:
        data = {"Course": []}
        for course in self.courses:
            c_data = {"Name": course.text(0), "Weight": course.text(1), "Grade": course.text(2),
                      "Expanded": course.isExpanded(), "Types": []}
            for i in range(course.childCount()):
                t = course.child(i)
                t_data = {"Name": t.text(0), "Weight": t.text(1), "Grade": t.text(2), "Expanded": t.isExpanded(),
                          "Assignments": []}
                for j in range(t.childCount()):
                    ass = t.child(j)
                    t_data["Assignments"].append({"Name": ass.text(0), "Weight": ass.text(1), "Grade": ass.text(2), "Extra Credit": ass.isExtraCredit()})
                c_data["Types"].append(t_data)
            data["Course"].append(c_data)

        with open(filename.replace(".grdb", "") + ".grdb", "w+") as f:
            json.dump(data, f)
        self.change_made = True
    return filename

def readJSON(self):
    filename, _ = QtWidgets.QFileDialog.getOpenFileName(self, "Select File", "",
                                                        "Gradebook Files (*.grdb)")
    if filename:
        with open(filename) as json_file:
            self.clearPage()
            self.filename = filename
            data = json.load(json_file)

            for course_dict in data["Course"]:
                course = Course(self.treeWidget, [course_dict["Name"], course_dict["Weight"], course_dict["Grade"]])
                course.setExpanded(course_dict["Expanded"])
                for type_dict in course_dict["Types"]:
                    t = AssignmentType(course, [type_dict["Name"], type_dict["Weight"], type_dict["Grade"]])
                    t.setExpanded(type_dict["Expanded"])
                    for assignment in type_dict["Assignments"]:
                        ass = Assignment(t, [assignment["Name"], assignment["Weight"], assignment["Grade"]])
                        if assignment["Extra Credit"]:
                            ass.setExtraCredit(True)
                            ass.setFont(0,extraCreditFont)
                        t.addChild(ass)
                    course.addChild(t)
                self.courses.append(course)
        self.change_made = False

def closeEvent(self, event):
    if self.change_made:
        event.ignore()
        answer = QtWidgets.QMessageBox.question(self, "Close Confirmation",
                                                "Would you like to save before exiting?",
                                                QtWidgets.QMessageBox.Yes | QtWidgets.QMessageBox.No | QtWidgets.QMessageBox.Cancel)

        if answer == QtWidgets.QMessageBox.Cancel:
            return
        elif answer == QtWidgets.QMessageBox.Yes:
            self.saveJSON()

        event.accept()

if name == "__main__":

import sys

app = QtWidgets.QApplication(sys.argv)
ui = Ui_MainWindow()
ui.setupUi()
ui.show()
sys.exit(app.exec_())

{"Course": [{"Name": "A Course", "Weight": "", "Grade": "0.9099999999999999", "Expanded": true, "Types": [{"Name": "Exams", "Weight": ".7", "Grade": "0.925", "Expanded": true, "Assignments": [{"Name": "Exam 1", "Weight": "", "Grade": "95/100", "Extra Credit": false}, {"Name": "Exam 2", "Weight": "", "Grade": ".9", "Extra Credit": false}]}, {"Name": "Quizzes", "Weight": "3/10", "Grade": "0.875", "Expanded": true, "Assignments": [{"Name": "Quiz 1", "Weight": "", "Grade": "8/10", "Extra Credit": false}, {"Name": "Quiz 2", "Weight": "", "Grade": ".95", "Extra Credit": false}, {"Name": "Quiz 3", "Weight": "", "Grade": "", "Extra Credit": false}]}]}]}