PyQt：QListView拖放重新排序信号问题

Question

使用QListView和QStandardItemModel实现拖放重新排序时遇到了一些麻烦。使用itemChanged信号处理已检查的项目很好，但是当使用拖放重新排序项目时，似乎在触发信号时会创建临时项目。列表中有5个项目，但每次重新排序项目时，模型行计数变为6，即使最终只有5个可见。当我专门设置要移动的动作时，为什么它会暂时变为6？我想处理新订单中的5个项目，因为列表直接用于更新另一个小部件。我尝试了dataChange信号，但没有区别。

我的设置是在Win 7上使用Python 2.7.10的PyQt 4.11.4。

import sys

from PyQt4.QtGui import *
from PyQt4.QtCore import *

if __name__ == '__main__':
    app = QApplication(sys.argv)

    # Our main window will be a QListView
    list = QListView()
    list.setDragDropMode(QAbstractItemView.InternalMove)
    list.setDefaultDropAction(Qt.MoveAction)
    list.setDragDropOverwriteMode(False)
    list.setAcceptDrops(True)
    list.setDropIndicatorShown(True)
    list.setDragEnabled(True)
    list.setWindowTitle('Example List')
    list.setMinimumSize(600, 400)

    # Create an empty model for the list's data
    model = QStandardItemModel(list)

    # Add some textual items
    foods = [
        'pizza',
        'burger',
        'steak',
        'chips',
        'soda'
    ]

    for food in foods:
        # create an item with a caption
        item = QStandardItem(food)

        # add a checkbox to it
        item.setCheckable(True)
        item.setData({'one': 1, 'two': 2, 'three': 3})
        item.setDragEnabled(True)
        item.setDropEnabled(False)

        # Add the item to the model
        model.appendRow(item)

    def on_item_changed(item):
        # If the changed item is not checked, don't bother checking others
        print 'DEBUG model rowcount'
        print model.rowCount()
        print 'itemChanged'
        if not item.checkState():
            return

        # Loop through the items until you get None, which
        # means you've passed the end of the list
        i = 0
        while model.item(i):
            if not model.item(i).checkState():
                return
            i += 1

        app.quit()

    model.itemChanged.connect(on_item_changed)

    # Apply the model to the list view
    list.setModel(model)

    w = QMainWindow()
    w.setCentralWidget(list)
    w.show()

    sys.exit(app.exec_())

Answer 1

更新，我发现了一个解决方法，它涉及使用单一计时器。删除列表中的项目后，计时器将触发插槽，并在新订单中找到5个项目而不是6个。

import sys

from PyQt4.QtGui import *
from PyQt4.QtCore import *

if __name__ == '__main__':
    app = QApplication(sys.argv)

    # Our main window will be a QListView
    list = QListView()
    list.setDragDropMode(QAbstractItemView.InternalMove)
    list.setDefaultDropAction(Qt.MoveAction)
    list.setDragDropOverwriteMode(False)
    list.setAcceptDrops(True)
    list.setDropIndicatorShown(True)
    list.setDragEnabled(True)
    list.setWindowTitle('Example List')
    list.setMinimumSize(600, 400)

    # Create an empty model for the list's data
    model = QStandardItemModel(list)

    # Add some textual items
    foods = [
        'pizza',
        'burger',
        'steak',
        'chips',
        'soda'
    ]

    for food in foods:
        # create an item with a caption
        item = QStandardItem(food)

        # add a checkbox to it
        item.setCheckable(True)
        item.setData({'one': 1, 'two': 2, 'three': 3})
        item.setDragEnabled(True)
        item.setDropEnabled(False)

        # Add the item to the model
        model.appendRow(item)

    def showModelCount():
        print 'DEBUG rowcount after singleshot'
        print model.rowCount()

    def on_item_changed(item):
        # If the changed item is not checked, don't bother checking others
        print 'DEBUG model rowcount'
        print model.rowCount()

        QTimer.singleShot(1, showModelCount)

        print 'itemChanged'
        if not item.checkState():
            return

        # Loop through the items until you get None, which
        # means you've passed the end of the list
        i = 0
        while model.item(i):
            if not model.item(i).checkState():
                return
            i += 1

        app.quit()

    model.itemChanged.connect(on_item_changed)

    # Apply the model to the list view
    list.setModel(model)

    w = QMainWindow()
    w.setCentralWidget(list)
    w.show()

    sys.exit(app.exec_())