可编辑可重排序(通过拖放)Qt5 QTreeView示例

我已经设法扩展了参考问题的答案，使模型项可以通过拖放重新排序。然而，我必须指出，所引用的示例和我的回答实际上都处理类似于列表模型的模型，而不是树模型，因为拖放并不影响模型项之间的父子关系，而是实现了拖放处理以始终执行项重新排序。

只要拖放需要对被重新定位的项的一些数据进行序列化，通过拖放进行重新排序可以通过以下方式实现:

1. 在拖动时，我们序列化一些关于被拖动项目的信息
2. On drop we:
   • 反序列化此信息返回
   • 使用此信息来定位每个拖动项在模型中的原始位置
   • 从模型中移除已定位的项目，从而导致剩余项目移动其位置;如果模型正确地实现了removeRows方法，Qt将为我们做。
   • 将被删除的项目插入到模型中，但这一次在项目之前或之后的位置。前一个选项用于掉落到第一个项目，后一个选项用于其他情况。

以下是PyQt4解决方案的完整代码:

import sys
from PyQt4 import QtGui, QtCore
class TreeModel(QtCore.QAbstractItemModel):
    def __init__(self):
        QtCore.QAbstractItemModel.__init__(self)
        self.nodes = ['node0', 'node1', 'node2', 'node3', 'node4', 'node5']
    def index(self, row, column, parent):
        if row < 0 or row >= len(self.nodes):
            return QtCore.QModelIndex()
        return self.createIndex(row, column, self.nodes[row])
    def parent(self, index):
        return QtCore.QModelIndex()
    def rowCount(self, index):
        if index.isValid():
            return 0
        if index.internalPointer() in self.nodes:
            return 0
        return len(self.nodes)
    def columnCount(self, index):
        if index.isValid():
            return 0
        return 1
    def data(self, index, role):
        if not index.isValid():
            return None
        if role == 0: 
            return index.internalPointer()
        else:
            return None
    def supportedDropActions(self): 
        return QtCore.Qt.CopyAction | QtCore.Qt.MoveAction         
    def flags(self, index):
        if not index.isValid():
            return QtCore.Qt.ItemIsEnabled
        return QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable | 
               QtCore.Qt.ItemIsDragEnabled | QtCore.Qt.ItemIsDropEnabled        
    def insertRows(self, row, count, index):
        if index.isValid():
            return False
        if count <= 0:
            return False
        # inserting 'count' empty rows starting at 'row'
        self.beginInsertRows(QtCore.QModelIndex(), row, row + count - 1)
        for i in range(0, count):
            self.nodes.insert(row + i, '')
        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.nodes.pop(row - i + 1)
        self.endRemoveRows()
        return True
    def setData(self, index, value, role):
        if not index.isValid():
            return False
        if index.row() < 0 or index.row() > len(self.nodes):
            return False
        self.nodes[index.row()] = str(value)
        self.dataChanged.emit(index, index)
    def mimeTypes(self):
        return ['application/vnd.treeviewdragdrop.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, 0)
                stream << QtCore.QString(text)
        mimedata.setData('application/vnd.treeviewdragdrop.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.treeviewdragdrop.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 and begin_row != 0:
            begin_row += 1
        encoded_data = data.data('application/vnd.treeviewdragdrop.list')
        stream = QtCore.QDataStream(encoded_data, QtCore.QIODevice.ReadOnly)
        new_items = []
        rows = 0
        while not stream.atEnd():
            text = QtCore.QString()
            stream >> text
            new_items.append(text)
            rows += 1
        # insert the new rows for the dropped items and set the data to these items appropriately
        self.insertRows(begin_row, rows, QtCore.QModelIndex())
        for text in new_items:
            idx = self.index(begin_row, 0, QtCore.QModelIndex())
            self.setData(idx, text, 0)
            self.dataChanged.emit(idx, idx)
            begin_row += 1
        return True
class MainForm(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MainForm, self).__init__(parent)
        self.treeModel = TreeModel()
        self.view = QtGui.QTreeView()
        self.view.setModel(self.treeModel)
        self.view.setDragDropMode(QtGui.QAbstractItemView.InternalMove)
        self.setCentralWidget(self.view)
def main():
    app = QtGui.QApplication(sys.argv)
    form = MainForm()
    form.show()
    app.exec_()
if __name__ == '__main__':
    main()

乌利希期刊指南。:如果有人感兴趣，我已经扩展了这个演示，以正确处理拖放后的选择，PyQt5和Python 3的代码可以在这里找到。