如何从一个QListWidget拖放到另一个

Question

有两个QListWIdgets位于同一个对话窗口中。已为两者启用DragDrop功能。如果我将文件拖放到两个ListWidges中的任何一个，程序会识别它并打印出丢弃的文件列表。但是除了拖放文件之外，我希望能够将List小部件项从一个拖放到另一个。如果我拖动ListItems，则会触发拖放事件。但它无法识别哪些项目被放到窗口小部件上。示例代码如下。目标是将列表项从一个ListWidget拖放到另一个ListWidget。

import sys, os
from PyQt4 import QtCore, QtGui   
class ThumbListWidget(QtGui.QListWidget):
    def __init__(self, type, parent=None):
        super(ThumbListWidget, self).__init__(parent)
        self.setAcceptDrops(True)
        self.setIconSize(QtCore.QSize(124, 124))

    def dragEnterEvent(self, event):
        if event.mimeData().hasUrls:
            event.accept()
        else:
            event.ignore()

    def dragMoveEvent(self, event):
        if event.mimeData().hasUrls:
            event.setDropAction(QtCore.Qt.CopyAction)
            event.accept()
        else:
            event.ignore()

    def dropEvent(self, event):
        if event.mimeData().hasUrls:
            event.setDropAction(QtCore.Qt.CopyAction)
            event.accept()
            links = []
            for url in event.mimeData().urls():
                links.append(str(url.toLocalFile()))
            self.emit(QtCore.SIGNAL("dropped"), links)
        else:
            event.ignore()


class Dialog_01(QtGui.QMainWindow):
    def __init__(self):
        super(QtGui.QMainWindow,self).__init__()
        self.listItems={}

        myQWidget = QtGui.QWidget()
        myBoxLayout = QtGui.QVBoxLayout()
        myQWidget.setLayout(myBoxLayout)
        self.setCentralWidget(myQWidget)

        self.listWidgetA = ThumbListWidget(self)
        for i in range(12): 
            QtGui.QListWidgetItem( 'Item '+str(i), self.listWidgetA )
        myBoxLayout.addWidget(self.listWidgetA)

        self.listWidgetB = ThumbListWidget(self)
        myBoxLayout.addWidget(self.listWidgetB)   

        self.listWidgetA.setDragDropMode(QtGui.QAbstractItemView.InternalMove)
        self.listWidgetA.setSelectionMode(QtGui.QAbstractItemView.ExtendedSelection)
        self.connect(self.listWidgetA, QtCore.SIGNAL("dropped"), self.items_dropped)
        self.listWidgetA.currentItemChanged.connect(self.item_clicked)

        self.listWidgetB.setDragDropMode(QtGui.QAbstractItemView.InternalMove)
        self.listWidgetB.setSelectionMode(QtGui.QAbstractItemView.ExtendedSelection)
        self.connect(self.listWidgetB, QtCore.SIGNAL("dropped"), self.items_dropped)
        self.listWidgetB.currentItemChanged.connect(self.item_clicked)

    def items_dropped(self, arg):
        print arg

    def item_clicked(self, arg):
        print arg

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    dialog_1 = Dialog_01()
    dialog_1.show()
    dialog_1.resize(480,320)
    sys.exit(app.exec_())

EDIT # 2

这是完成所有工作的代码。但是没有办法追踪丢弃的物体。 lostOnA（）和droppedOnB（）方法仍然无法正常工作。

---

from PyQt4 import QtGui, QtCore
import sys, os


class MyClassItem(QtGui.QListWidgetItem):
    def __init__(self, parent=None):
        super(QtGui.QListWidgetItem, self).__init__(parent)       


class ThumbListWidget(QtGui.QListWidget):
    def __init__(self, type, parent=None):
        super(ThumbListWidget, self).__init__(parent)
        self.setIconSize(QtCore.QSize(124, 124))
        self.setDragDropMode(QtGui.QAbstractItemView.DragDrop)
        self.setSelectionMode(QtGui.QAbstractItemView.ExtendedSelection)
        self.setAcceptDrops(True)

    def dragEnterEvent(self, event):
        if event.mimeData().hasUrls():
            event.accept()
        else:
            super(ThumbListWidget, self).dragEnterEvent(event)

    def dragMoveEvent(self, event):
        if event.mimeData().hasUrls():
            event.setDropAction(QtCore.Qt.CopyAction)
            event.accept()
        else:
            super(ThumbListWidget, self).dragMoveEvent(event)

    def dropEvent(self, event):
        print 'dropEvent', event
        if event.mimeData().hasUrls():
            event.setDropAction(QtCore.Qt.CopyAction)
            event.accept()
            links = []
            for url in event.mimeData().urls():
                links.append(str(url.toLocalFile()))
            self.emit(QtCore.SIGNAL("dropped"), links)
        else:
            event.setDropAction(QtCore.Qt.MoveAction)
            super(ThumbListWidget, self).dropEvent(event)


class Dialog_01(QtGui.QMainWindow):
    def __init__(self):
        super(QtGui.QMainWindow,self).__init__()
        self.listItems={}

        myQWidget = QtGui.QWidget()
        myBoxLayout = QtGui.QVBoxLayout()
        myQWidget.setLayout(myBoxLayout)
        self.setCentralWidget(myQWidget)

        self.listWidgetA = ThumbListWidget(self)
        self.listWidgetB = ThumbListWidget(self)

        for i in range(7):
            listItemAInstance=MyClassItem()
            listItemAInstance.setText('A'+'%04d'%i)
            listItemAInstance.setBackgroundColor(QtCore.Qt.darkGray)   
            if i%2: listItemAInstance.setBackgroundColor(QtCore.Qt.gray)
            self.listWidgetA.addItem(listItemAInstance) 

            listItemBInstance=MyClassItem()
            listItemBInstance.setText('B'+'%04d'%i)

            if i%2: listItemBInstance.setBackgroundColor(QtCore.Qt.lightGray)
            self.listWidgetB.addItem(listItemBInstance) 

        myBoxLayout.addWidget(self.listWidgetA)      

        myBoxLayout.addWidget(self.listWidgetB)   
        self.connect(self.listWidgetA, QtCore.SIGNAL("dropped"), self.droppedOnA)
        self.connect(self.listWidgetB, QtCore.SIGNAL("dropped"), self.droppedOnB)


    def droppedOnA(self, arg):
        print '\n\t droppedOnA', arg.text

    def droppedOnB(self, arg):
        print '\n\t droppedOnB', arg.text


if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    dialog_1 = Dialog_01()
    dialog_1.show()
    dialog_1.resize(480,320)
    sys.exit(app.exec_())

EDIT # 3

这次是另一次尝试使用MIME将已删除的Items对象传递给QListWidget。不幸的是，cPickle拒绝接受投掷的二进制对象

TypeError：sip.wrapper类型无法实例化或子类

为了解决这个问题，我将每个对象名称转换为字符串，并将其与self.listItems = {}字典一起用作检索列表项的二进制对象的键。这似乎运作良好。但最后，当我几乎完成所有操作时，没有可见错误的ListWidget不会将删除的列表项添加到自身......这很奇怪。

self.listWidgetB.addItem（droppedItemInstance）

.

---

from PyQt4 import QtGui, QtCore
import sys, os
import cPickle 

class MyClassItem(QtGui.QListWidgetItem):
    def __init__(self, parent=None):
        super(QtGui.QListWidgetItem, self).__init__(parent)       


class ThumbListWidget(QtGui.QListWidget):
    def __init__(self, type, parent=None):
        super(ThumbListWidget, self).__init__(parent)
        self.setIconSize(QtCore.QSize(124, 124))
        self.setDragDropMode(QtGui.QAbstractItemView.DragDrop)
        self.setSelectionMode(QtGui.QAbstractItemView.ExtendedSelection)
        self.setAcceptDrops(True)

    def dragEnterEvent(self, event):
        if event.mimeData().hasUrls():
            event.accept()
        else:
            super(ThumbListWidget, self).dragEnterEvent(event)

    def dragMoveEvent(self, event):
        if event.mimeData().hasUrls():
            event.setDropAction(QtCore.Qt.CopyAction)
            event.accept()
        else:
            super(ThumbListWidget, self).dragMoveEvent(event)

    def dropEvent(self, event):

        if event.mimeData().hasUrls():
            event.setDropAction(QtCore.Qt.CopyAction)
            event.accept()
            links = []
            for url in event.mimeData().urls():
                links.append(str(url.toLocalFile()))

        else:
            event.setDropAction(QtCore.Qt.MoveAction)
            super(ThumbListWidget, self).dropEvent(event)


    def mimeTypes(self):
        return ['bstream', 'text/xml']

    def mimeData(self, droppedItems):
        mimedata = QtCore.QMimeData()

        droppedItemsAsStrings=[]
        for each in droppedItems:            
            droppedItemsAsStrings.append( str(each) )

        bstream = cPickle.dumps(droppedItemsAsStrings)
        mimedata.setData('bstream', bstream)        
        return mimedata


    def dropMimeData(self, action, mimedata, row):

        if action == QtCore.Qt.IgnoreAction: return True  

        dropped=cPickle.loads(str(mimedata.data('bstream')))

        self.emit(QtCore.SIGNAL("dropped"), dropped)  

        return True


class Dialog_01(QtGui.QMainWindow):
    def __init__(self):
        super(QtGui.QMainWindow,self).__init__()
        self.listItems={}

        myQWidget = QtGui.QWidget()
        myBoxLayout = QtGui.QVBoxLayout()
        myQWidget.setLayout(myBoxLayout)
        self.setCentralWidget(myQWidget)

        self.listWidgetA = ThumbListWidget(self)
        self.listWidgetB = ThumbListWidget(self)

        for i in range(7):
            listItemAInstance=MyClassItem()
            listItemAInstance.setText('A'+'%04d'%i)
            listItemAInstance.setBackgroundColor(QtCore.Qt.darkGray)   
            if i%2: listItemAInstance.setBackgroundColor(QtCore.Qt.gray)
            self.listWidgetA.addItem(listItemAInstance) 

            listItemBInstance=MyClassItem()
            listItemBInstance.setText('B'+'%04d'%i)

            if i%2: listItemBInstance.setBackgroundColor(QtCore.Qt.lightGray)
            self.listWidgetB.addItem(listItemBInstance) 

            self.listItems[str(listItemAInstance)]=listItemAInstance
            self.listItems[str(listItemBInstance)]=listItemBInstance

        myBoxLayout.addWidget(self.listWidgetA)      

        myBoxLayout.addWidget(self.listWidgetB)   
        self.connect(self.listWidgetA, QtCore.SIGNAL("dropped"), self.droppedOnA)
        self.connect(self.listWidgetB, QtCore.SIGNAL("dropped"), self.droppedOnB)


    def droppedOnA(self, droppedItemsAsStrings):
        print '\n\t droppedOnA()'
        for each in droppedItemsAsStrings:
            if each in self.listItems.keys():
                droppedItemInstance = self.listItems[each]
                print 'adding', droppedItemInstance.text()
                self.listWidgetA.addItem(droppedItemInstance) 


    def droppedOnB(self, droppedItemsAsStrings):
        print '\n\t droppedOnB()'
        for each in droppedItemsAsStrings:
            if each in self.listItems.keys():
                droppedItemInstance = self.listItems[each]
                self.listWidgetB.addItem(droppedItemInstance) 
                print 'adding', droppedItemInstance.text()


if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    dialog_1 = Dialog_01()
    dialog_1.show()
    dialog_1.resize(480,320)
    sys.exit(app.exec_())

Answer 1

这是修改后的代码。它的工作就像一个魅力！好样的！

from PyQt4 import QtGui, QtCore
import sys, os

class ThumbListWidget(QtGui.QListWidget):
    def __init__(self, type, parent=None):
        super(ThumbListWidget, self).__init__(parent)
        self.setIconSize(QtCore.QSize(124, 124))
        self.setDragDropMode(QtGui.QAbstractItemView.DragDrop)
        self.setSelectionMode(QtGui.QAbstractItemView.ExtendedSelection)
        self.setAcceptDrops(True)

    def dragEnterEvent(self, event):
        if event.mimeData().hasUrls():
            event.accept()
        else:
            super(ThumbListWidget, self).dragEnterEvent(event)

    def dragMoveEvent(self, event):
        if event.mimeData().hasUrls():
            event.setDropAction(QtCore.Qt.CopyAction)
            event.accept()
        else:
            super(ThumbListWidget, self).dragMoveEvent(event)

    def dropEvent(self, event):
        print 'dropEvent', event
        if event.mimeData().hasUrls():
            event.setDropAction(QtCore.Qt.CopyAction)
            event.accept()
            links = []
            for url in event.mimeData().urls():
                links.append(str(url.toLocalFile()))
            self.emit(QtCore.SIGNAL("dropped"), links)
        else:
            event.setDropAction(QtCore.Qt.MoveAction)
            super(ThumbListWidget, self).dropEvent(event)


class Dialog_01(QtGui.QMainWindow):
    def __init__(self):
        super(QtGui.QMainWindow,self).__init__()
        self.listItems={}

        myQWidget = QtGui.QWidget()
        myBoxLayout = QtGui.QVBoxLayout()
        myQWidget.setLayout(myBoxLayout)
        self.setCentralWidget(myQWidget)

        self.listWidgetA = ThumbListWidget(self)
        for i in range(12): 
            QtGui.QListWidgetItem( 'Item '+str(i), self.listWidgetA )
        myBoxLayout.addWidget(self.listWidgetA)

        self.listWidgetB = ThumbListWidget(self)
        myBoxLayout.addWidget(self.listWidgetB)   

        self.connect(self.listWidgetA, QtCore.SIGNAL("dropped"), self.items_dropped)
        self.listWidgetA.currentItemChanged.connect(self.item_clicked)

        self.connect(self.listWidgetB, QtCore.SIGNAL("dropped"), self.items_dropped)
        self.listWidgetB.currentItemChanged.connect(self.item_clicked)

    def items_dropped(self, arg):
        print 'items_dropped', arg

    def item_clicked(self, arg):
        print arg

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    dialog_1 = Dialog_01()
    dialog_1.show()
    dialog_1.resize(480,320)
    sys.exit(app.exec_())

Answer 2

假设您要移动list-widget项，您的子类应如下所示（请注意setDragDropMode和setSelectionMode已移入__init__）：

class ThumbListWidget(QtGui.QListWidget):
    def __init__(self, type, parent=None):
        super(ThumbListWidget, self).__init__(parent)
        self.setIconSize(QtCore.QSize(124, 124))
        self.setDragDropMode(QtGui.QAbstractItemView.DragDrop)
        self.setSelectionMode(QtGui.QAbstractItemView.ExtendedSelection)
        self.setAcceptDrops(True)

    def dragEnterEvent(self, event):
        if event.mimeData().hasUrls():
            event.accept()
        else:
            super(ThumbListWidget, self).dragEnterEvent(event)

    def dragMoveEvent(self, event):
        if event.mimeData().hasUrls():
            event.setDropAction(QtCore.Qt.CopyAction)
            event.accept()
        else:
            super(ThumbListWidget, self).dragMoveEvent(event)

    def dropEvent(self, event):
        if event.mimeData().hasUrls():
            event.setDropAction(QtCore.Qt.CopyAction)
            event.accept()
            links = []
            for url in event.mimeData().urls():
                links.append(str(url.toLocalFile()))
            self.emit(QtCore.SIGNAL("dropped"), links)
        else:
            event.setDropAction(QtCore.Qt.MoveAction)
            super(ThumbListWidget, self).dropEvent(event)

Answer 3

在实现super()的Python 3风格时，上面的代码对我不起作用。

问题是继承的方法dragMoveEvent和dragDropEvent没有被子类中的新定义覆盖。

因此，没有调用event.setDropAction(QtCore.Qt.MoveAction)，并且小部件行为默认为QtCore.Qt.CopyAction。

我使用继承自setDefaultDropAction()类的QAbstractItemView方法解决了这个问题。

这是PyQt5和Python 3.7中的实现：

class NewDragDropWidget(QListWidget):

    def __init__(self):
        super().__init__()
        self.setIconSize(QtCore.QSize(124, 124))
        self.setDragDropMode(QAbstractItemView.DragDrop)
        self.setDefaultDropAction(QtCore.Qt.MoveAction) # this was the magic line
        self.setSelectionMode(QAbstractItemView.ExtendedSelection)
        self.setAcceptDrops(True)