PyQt：QListView拖放重新排序信號問題

Question

我在使用QListView和QStandardItemModel實現拖放重新排序時遇到了一些麻煩。 使用itemChanged信號來處理選中的項目很好，但是當使用拖放對項目進行重新排序時，似乎會在觸發信號時創建一個臨時項目。 列表中有5個項目，但是每次重新排序項目時，即使最后只有5個可見，模型行計數也變為6。 當我專門設置動作要移動時，為什么會暫時變為6？ 我只想處理新訂單中的5個項目，因為該列表直接用於更新另一個小部件。 我嘗試了dataChange信號，但沒有區別。

我的設置是在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，我發現了一個解決方法，它涉及使用單發計時器。 將項目放到列表中后，計時器會觸發該廣告位，並以新的順序找到5個項目，而不是6個項目。

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_())