PySide填充空TableModel

Question

我编写了一个并排有两个表视图的工具。我在它们之间拖放数据。一切都很好，但是不能让一个空的模型工作。所以在开始的时候，我想要有一个空的TableView，并通过拖放来添加项目。当至少有一个对象在，但不是空的对象时，这是有效的。如果是空的，甚至连头都没有。

我认为问题在于当模型为空时，TableView不会将其称为headerData……但是不知道这是不是对的。这是我的模型

如果我不设置空模型，但等到模型中有一个项目，然后再设置它，这将会起作用。但这并不是真的很好。

class myTableModel(TableModel):
    def __init__(self, headers = [], items = [[]], parent = None):
        super(myTableModel,self).__init__(headers,items,parent)
        self.__items = items
        self.__headers = headers

    def flags(self, index):
        if not index.isValid():
            return QtCore.Qt.ItemIsEnabled
        if index.column() == 0:
            return QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsDragEnabled | QtCore.Qt.ItemIsDropEnabled | QtCore.Qt.ItemIsEditable
        return QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsDragEnabled | QtCore.Qt.ItemIsDropEnabled

    def supportedDropActions(self): 
        return QtCore.Qt.CopyAction | QtCore.Qt.MoveAction    

    def removeRow(self, row, index=QtCore.QModelIndex()):
        self.beginRemoveRows(QtCore.QModelIndex(), row, row)
        self.__items.pop(row)
        self.endRemoveRows()
        return True

    def insertRow(self, data,row=0,index=QtCore.QModelIndex()):
        self.beginInsertRows(QtCore.QModelIndex(), 0,0)
        self.__items.insert(0, data)
        self.endInsertRows()
        return True        
    def data(self,index,role=QtCore.Qt.DisplayRole):
        if role == QtCore.Qt.DisplayRole:
            row = index.row()
            column = index.column()

            if len(self.__items[row])-1 < column:
                return ""
            else:
                return self.__items[row][column]

    def setData(self, index, value, role=QtCore.Qt.EditRole):
        if role == QtCore.Qt.EditRole:
            row = index.row()
            column = index.column()
            self.__items[row][column] = value
            self.dataChanged.emit(index, index)
            return True

    def headerData(self, section, orientation, role):
        if role == QtCore.Qt.DisplayRole:
            if orientation == QtCore.Qt.Horizontal:
                if len(self.__headers)-1 < section:
                    return ""
                else:
                    #print "%s in section %i" %(self.__headers[section],section)
                    return self.__headers[section]   

Answer 1

我可能来不及想出答案了，但这个问题本身对我来说很有趣，所以我深入研究，找到了解决方案。

事实证明，以这样一种方式实现表模型的空状态有几个陷阱，即它仍然显示列标题，并且还允许将内容放在它自己上。

第一个问题是，如果columnCount方法为无效的QModelIndex返回0，Qt似乎不会绘制列标题。在这种情况下，它看起来甚至不会调用headerData方法。解决方案是永远不要用无效的QModelIndex从columnCount返回0，即使行数实际上是0，并且我们的底层数据结构是一个二维数组，其中0行表示0列。

第二个陷阱是，您似乎需要一个自定义视图的子类化QTableView，因为您需要重写dragEnterEvent和dragMoveEvent来接受拖动输入和拖动移动unconditionally.否则，即使将视图的acceptDrops属性设置为True，drop事件也没有触发的机会。dragEnterEvent和/或dragMoveEvent的默认实现似乎与视图的底层模型对话，如果模型没有行，则视图拒绝接受丢弃。

第三个陷阱并不是什么陷阱，它只是在你的模型的dropMimeData方法中，如果没有插入行，你需要插入行，以便为被丢弃的项腾出空间。

以下是使用Python2.7测试的PySide 1.2.1 / Qt 4.8.5的完整解决方案：

import sys
from PySide import QtCore, QtGui

class TableModel(QtCore.QAbstractTableModel):
    def __init__(self, headers = [], items = [[]], parent = None):
        super(TableModel,self).__init__(parent)
        self.__items = items
        self.__headers = headers

        row_counter = 0
        for row_item in self.__items:
            column_counter = 0
            for column_item in row_item:
                idx = self.createIndex(row_counter, column_counter)
                self.setData(idx, column_item, QtCore.Qt.EditRole)
                self.dataChanged.emit(idx, idx)
                column_counter += 1
            row_counter += 1        

        num_headers = len(self.__headers)
        for section in range(0, num_headers):
            self.setHeaderData(section, QtCore.Qt.Horizontal, self.__headers[section])
        self.headerDataChanged.emit(QtCore.Qt.Horizontal, 0, num_headers)

    def index(self, row, column, parent):
        if row < 0 or row >= len(self.__items):
            return QtCore.QModelIndex()
        return self.createIndex(row, column, self.__items[row])

    def parent(self, index):
        return QtCore.QModelIndex()

    def rowCount(self, index):
        if index.isValid():
            return 

        num_rows = len(self.__items)

        # checking for empty nested columns list within a single "row"
        if num_rows == 1:
            if len(self.__items[0]) == 0:
                return 0

        return num_rows

    def columnCount(self, index):
        if index.isValid():
            return 0

        # compute the max column count within all rows
        max_column_count = 0
        for row in self.__items:
            column_count = len(row)
            if column_count > max_column_count:
                max_column_count = column_count

        # if there are no real columns, make the column count return the number of headers instead
        if max_column_count < len(self.__headers):
            max_column_count = len(self.__headers)
        return max_column_count

    def flags(self, index):
        if not index.isValid():
            return QtCore.Qt.ItemIsEnabled
        if index.column() == 0:
            return QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsDragEnabled | \
                   QtCore.Qt.ItemIsDropEnabled | QtCore.Qt.ItemIsEditable
        return QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable | \
               QtCore.Qt.ItemIsDragEnabled | QtCore.Qt.ItemIsDropEnabled

    def supportedDropActions(self): 
        return QtCore.Qt.CopyAction | QtCore.Qt.MoveAction    

    def insertRows(self, row, count, index):
        if index.isValid():
            return False
        if count <= 0:
            return False
        num_columns = self.columnCount(index)
        # inserting 'count' empty rows starting at 'row'
        self.beginInsertRows(QtCore.QModelIndex(), row, row + count - 1)
        for i in range(0, count):
            # inserting as many columns as the table currently has
            self.__items.insert(row + i, ["" for i in range(0, num_columns)])
        self.endInsertRows()
        return True

    def removeRows(self, row, count, index):
        if index.isValid():
            return False
        if count <= 0:
            return False
        num_rows = self.rowCount(QtCore.QModelIndex())
        self.beginRemoveRows(QtCore.QModelIndex(), row, row + count - 1)
        for i in range(count, 0, -1):
            self.__items.pop(row - i + 1)
        self.endRemoveRows()
        return True

    def data(self,index,role=QtCore.Qt.DisplayRole):
        if role == QtCore.Qt.DisplayRole:
            row = index.row()
            column = index.column()
            if row < 0 or row >= len(self.__items):
                return ""
            if column < 0 or column >= len(self.__items[row]):
                return ""
            else:
                return self.__items[row][column]
        return None

    def setData(self, index, value, role=QtCore.Qt.EditRole):
        if not index.isValid:
            return False
        if role == QtCore.Qt.EditRole:
            row = index.row()
            column = index.column()
            if row < 0 or row >= self.rowCount(QtCore.QModelIndex()):
                return False
            if column < 0 or column >= len(self.__items[row]):
                return False
            self.__items[row].pop(column)
            self.__items[row].insert(column, value)
            self.dataChanged.emit(index, index)
            return True
        return False

    def headerData(self, section, orientation, role):
        if role == QtCore.Qt.DisplayRole:
            if orientation == QtCore.Qt.Horizontal:
                if section < 0 or section >= len(self.__headers):
                    return ""
                else:
                    return self.__headers[section]
        return None

    def mimeTypes(self):
        return ['application/vnd.tableviewdragdrop.list']

    def mimeData(self, indexes):
        mimedata = QtCore.QMimeData()
        encoded_data = QtCore.QByteArray()
        stream = QtCore.QDataStream(encoded_data, QtCore.QIODevice.WriteOnly)
        for index in indexes:
            if index.isValid():
                text = self.data(index, QtCore.Qt.DisplayRole)
                stream << QtCore.QByteArray(text)
        mimedata.setData('application/vnd.tableviewdragdrop.list', encoded_data)
        return mimedata

    def dropMimeData(self, data, action, row, column, parent):
        if action == QtCore.Qt.IgnoreAction:
            return True
        if not data.hasFormat('application/vnd.tableviewdragdrop.list'):
            return False
        if column > 0:
            return False

        num_rows = self.rowCount(QtCore.QModelIndex())

        begin_row = 0
        if row != -1:
            begin_row = row
        elif parent.isValid():
            begin_row = parent.row()
        else:
            begin_row = num_rows

        if begin_row == num_rows:
            self.insertRows(begin_row, 1, QtCore.QModelIndex())

        if column < 0:
            if parent.isValid():
                column = parent.column()
            else:
                column = 0

        encoded_data = data.data('application/vnd.tableviewdragdrop.list')
        stream = QtCore.QDataStream(encoded_data, QtCore.QIODevice.ReadOnly)
        new_items = []
        rows = 0
        while not stream.atEnd():
            text = QtCore.QByteArray()
            stream >> text
            new_items.append(str(text))
            rows += 1

        for text in new_items:
            idx = self.index(begin_row, column, QtCore.QModelIndex())
            self.setData(idx, text, QtCore.Qt.EditRole)
            begin_row += 1

        return True

class TableView(QtGui.QTableView):
    def __init__(self, parent=None):
        super(TableView, self).__init__(parent)
        self.setAcceptDrops(True)

    def dragEnterEvent(self, event):
        event.accept()

    def dragMoveEvent(self, event):
        event.accept()

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

        self.left_model = TableModel(headers=["column0", "column1", "column2"])
        #self.left_model = TableModel(items=[["left0", "left1", "left2"],["left3","left4","left5"]],
        #                             headers=["column0", "column1", "column2"])
        self.right_model = TableModel(items=[['right0', 'right1', 'right2'], ['right3', 'right4', 'right5']],
                                      headers=['column0', 'column1', 'column2'])

        self.left_view = TableView()
        self.left_view.setModel(self.left_model)
        self.left_view.setDragDropMode(QtGui.QAbstractItemView.DragDrop)

        self.right_view = TableView()
        self.right_view.setModel(self.right_model)
        self.right_view.setDragDropMode(QtGui.QAbstractItemView.DragDrop)

        self.layout = QtGui.QHBoxLayout()
        self.layout.addWidget(self.left_view)
        self.layout.addWidget(self.right_view)

        self.window = QtGui.QWidget()
        self.window.setLayout(self.layout)

        self.setCentralWidget(self.window)

def main():
    app = QtGui.QApplication(sys.argv)
    form = MainForm()
    form.show()
    app.exec_()

if __name__ == '__main__':
    main()