如何从ListWidget拖放到ComboBox

Question

我们的目标是能够把列表中的项目拖到下拉框（comboBox）上。被拖放的项目应该被添加到下拉框里。理想情况下，我们希望避免使用一些技巧，比如读取列表中当前选中的项目或其他类似的操作……有什么好的想法吗？

from PyQt4 import QtGui, QtCore
import sys, os

class MyClass(object):
    def __init__(self):
        super(MyClass, self).__init__()
        self.name=None     
    def setName(self, arg):
        self.name=arg
    def getName(self):
        return self.name       

class DropableComboBox(QtGui.QComboBox):
    def __init__(self):
        self.model_mime_type = 'application/x-qabstractitemmodeldatalist'
        super(DropableComboBox, self).__init__()
        self.setAcceptDrops(True)

    def dragEnterEvent(self, event):
        if event.mimeData().hasFormat(self.model_mime_type) or event.mimeData().hasFormat('text/plain'):
            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:
            super(DropableComboBox, self).dropEvent(event)
            self.emit(QtCore.SIGNAL("dropped"))

class Dialog_01(QtGui.QMainWindow):
    def __init__(self):
        super(QtGui.QMainWindow,self).__init__()

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

        self.listWidget = QtGui.QListWidget()
        self.listWidget.setDragDropMode(QtGui.QAbstractItemView.DragDrop)
        self.listWidget.setSelectionMode(QtGui.QAbstractItemView.ExtendedSelection)
        self.listWidget.currentItemChanged.connect(self.item_clicked)

        for i in range(3):
            my_item=QtGui.QListWidgetItem()
            name='ListWidget Item '+str(i)
            my_item.setText(name)
            self.listWidget.addItem(my_item)

            myObject=MyClass()
            myObject.setName(name) 

            my_item.setData(QtCore.Qt.UserRole, myObject)

        myBoxLayout.addWidget(self.listWidget)

        self.ComboBox = DropableComboBox()
        for i in range(3):
            self.ComboBox.addItem("Combobox Item " + str(i))

        self.ComboBox.currentIndexChanged.connect(self.combobox_selected)
        self.connect(self.ComboBox, QtCore.SIGNAL("dropped"), self.droppedOnCombobox)

        myBoxLayout.addWidget(self.ComboBox)

    def item_clicked(self, arg=None):
        print arg.data(QtCore.Qt.UserRole).toPyObject().getName()

    def combobox_selected(self, index):
        myObject=self.ComboBox.itemData(index).toPyObject()
        if hasattr(myObject, 'getName'): print myObject.getName()

    def droppedOnCombobox(self):
        print "Drop!"


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

要做到这一点的“正确”方法是使用 QDataStream 来解包数据。不过，这似乎需要用到 QMap，而在 PyQt 中是没有这个的。所以我们可以用一种稍微“黑科技”或者说“巧妙”的方法，让一个代理模型来帮我们处理这个问题：

class DropableComboBox(QtGui.QComboBox):
    def __init__(self):
        super(DropableComboBox, self).__init__()
        self.model_mime_type = 'application/x-qabstractitemmodeldatalist'
        self.setAcceptDrops(True)
        self._proxymodel = QtGui.QStandardItemModel(self)

    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)
        elif event.mimeData().hasFormat(self.model_mime_type):
            self._proxymodel.setRowCount(0)
            self._proxymodel.dropMimeData(
                event.mimeData(), QtCore.Qt.CopyAction,
                0, 0, QtCore.QModelIndex())
            for index in range(self._proxymodel.rowCount()):
                item = self._proxymodel.item(index, 0)                  
                self.addItem(item.text())
            # no point calling the base-class dropEvent here,
            # because it's a NO-OP in QComboBox
            self.emit(QtCore.SIGNAL("dropped"))

注意：

这样做会是从列表小部件中 复制 项目，而不是 移动 它们（这不是你问的）。另外，如果你想防止重复项被添加，可以使用 setDuplicatesEnabled。如果你想改变添加项目的方式，可以使用 setInsertPolicy。