python3+PyQt5重新实现自定义数据拖放处理

本文分成两部分，第一部分通过python3+PyQt5实现自定义数据的拖放操作。第二部分则对第一部分的程序进行修改，增加拖放操作时，菜单提示是否移动或拷贝，还有可以通过ctrl键盘来设置移动过程中拷贝源而非会将源删除。

自定义数据MIME数据类型QMimeData，MIME是一种用于处理具有多个组成部分的自定义数据的标准化格式。MIME数据由一个数据类型和一个子类型构成–例如，text/plain，text/html，image/png，要处理自定义MIME数据，就必须要选用一种自定义数据类型和一种子类型，然后将数据封装到QMimeData对象中。本例子中，我们创建端为application/x-icon-and-text类型的新MIME数据。

注：

dragEnterEvent这是一个拖拽事件的函数，我们把文件拖拽进程序界面打开，之前必须setAcceptDrops(true)了以后拖拽，但是只设置acceptDrops还不够，还需要在dragEnterEvent事件中对拖入的对象进行筛选，判断mimeData的类型是否是你能处理的，如果是，则调用event.acceptProposedAction()放行。拖放结束后会产生dropEvent事件，在那里进行最后的放置操作。总之这是拖拽事件函数的一个筛选事件并放置的函数。

第一部分：

#!/usr/bin/env python3import osimport sysfrom PyQt5.QtCore import (QByteArray, QDataStream, QIODevice, QMimeData,    QPoint, QSize, Qt)from PyQt5.QtWidgets import (QApplication, QDialog,QGridLayout,               QLineEdit, QListWidget,QListWidgetItem, QWidget)from PyQt5.QtGui import QIcon,QColor,QPainter,QFontMetricsF,QDragclass DropLineEdit(QLineEdit):  def __init__(self, parent=None):    super(DropLineEdit, self).__init__(parent)    self.setAcceptDrops(True)  def dragEnterEvent(self, event):    if event.mimeData().hasFormat("application/x-icon-and-text"):      event.accept()    else:      event.ignore()  def dragMoveEvent(self, event):    if event.mimeData().hasFormat("application/x-icon-and-text"):      event.setDropAction(Qt.CopyAction)      event.accept()    else:      event.ignore()  def dropEvent(self, event):    if event.mimeData().hasFormat("application/x-icon-and-text"):      data = event.mimeData().data("application/x-icon-and-text")      stream = QDataStream(data, QIODevice.ReadOnly)      text = ""      #stream >> text      text=stream.readQString()      self.setText(text)      event.setDropAction(Qt.CopyAction)      event.accept()    else:      event.ignore()class DnDListWidget(QListWidget):  def __init__(self, parent=None):    super(DnDListWidget, self).__init__(parent)    self.setAcceptDrops(True)    self.setDragEnabled(True)  def dragEnterEvent(self, event):    if event.mimeData().hasFormat("application/x-icon-and-text"):      event.accept()    else:      event.ignore()  def dragMoveEvent(self, event):    if event.mimeData().hasFormat("application/x-icon-and-text"):      event.setDropAction(Qt.MoveAction)      event.accept()    else:      event.ignore()  def dropEvent(self, event):    if event.mimeData().hasFormat("application/x-icon-and-text"):      data = event.mimeData().data("application/x-icon-and-text")      stream = QDataStream(data, QIODevice.ReadOnly)      text = ""      icon = QIcon()      #stream >> text >> icon      text=stream.readQString()      stream >> icon      item = QListWidgetItem(text, self)      item.setIcon(icon)      event.setDropAction(Qt.MoveAction)      event.accept()    else:      event.ignore()  def startDrag(self, dropActions):    item = self.currentItem()    icon = item.icon()    data = QByteArray()    stream = QDataStream(data, QIODevice.WriteOnly)    #stream << item.text() << icon    stream.writeQString(item.text())    stream << icon    mimeData = QMimeData()    mimeData.setData("application/x-icon-and-text", data)    drag = QDrag(self)    drag.setMimeData(mimeData)    pixmap = icon.pixmap(24, 24)    drag.setHotSpot(QPoint(12, 12))    drag.setPixmap(pixmap)    if drag.exec(Qt.MoveAction) == Qt.MoveAction:      self.takeItem(self.row(item))class DnDWidget(QWidget):  def __init__(self, text, icon=QIcon(), parent=None):    super(DnDWidget, self).__init__(parent)    self.setAcceptDrops(True)    self.text = text    self.icon = icon  def minimumSizeHint(self):    fm = QFontMetricsF(self.font())    if self.icon.isNull():      return QSize(fm.width(self.text), fm.height() * 1.5)    return QSize(34 + fm.width(self.text), max(34, fm.height() * 1.5))  def paintEvent(self, event):    height = QFontMetricsF(self.font()).height()    painter = QPainter(self)    painter.setRenderHint(QPainter.Antialiasing)    painter.setRenderHint(QPainter.TextAntialiasing)    painter.fillRect(self.rect(), QColor(Qt.yellow).lighter())    if self.icon.isNull():      painter.drawText(10, height, self.text)    else:      pixmap = self.icon.pixmap(24, 24)      painter.drawPixmap(0, 5, pixmap)      painter.drawText(34, height,               self.text + " (Drag to or from me!)")  def dragEnterEvent(self, event):    if event.mimeData().hasFormat("application/x-icon-and-text"):      event.accept()    else:      event.ignore()  def dragMoveEvent(self, event):    if event.mimeData().hasFormat("application/x-icon-and-text"):      event.setDropAction(Qt.CopyAction)      event.accept()    else:      event.ignore()  def dropEvent(self, event):    if event.mimeData().hasFormat("application/x-icon-and-text"):      data = event.mimeData().data("application/x-icon-and-text")      stream = QDataStream(data, QIODevice.ReadOnly)      self.text = ""      self.icon = QIcon()      #stream >> self.text >> self.icon      self.text=stream.readQString()      stream>>self.icon      event.setDropAction(Qt.CopyAction)      event.accept()      self.updateGeometry()      self.update()    else:      event.ignore()  def mouseMoveEvent(self, event):    self.startDrag()    QWidget.mouseMoveEvent(self, event)  def startDrag(self):    icon = self.icon    if icon.isNull():      return    data = QByteArray()    stream = QDataStream(data, QIODevice.WriteOnly)    #stream << self.text << icon    stream.writeQString(self.text)    stream<<icon    mimeData = QMimeData()    mimeData.setData("application/x-icon-and-text", data)    drag = QDrag(self)    drag.setMimeData(mimeData)    pixmap = icon.pixmap(24, 24)    drag.setHotSpot(QPoint(12, 12))    drag.setPixmap(pixmap)    drag.exec(Qt.CopyAction)class Form(QDialog):  def __init__(self, parent=None):    super(Form, self).__init__(parent)    dndListWidget = DnDListWidget()    path = os.path.dirname(__file__)    for image in sorted(os.listdir(os.path.join(path, "images"))):      if image.endswith(".png"):        item = QListWidgetItem(image.split(".")[0].capitalize())        item.setIcon(QIcon(os.path.join(path,                  "images/{0}".format(image))))        dndListWidget.addItem(item)    dndIconListWidget = DnDListWidget()    dndIconListWidget.setViewMode(QListWidget.IconMode)    dndWidget = DnDWidget("Drag to me!")    dropLineEdit = DropLineEdit()    layout = QGridLayout()    layout.addWidget(dndListWidget, 0, 0)    layout.addWidget(dndIconListWidget, 0, 1)    layout.addWidget(dndWidget, 1, 0)    layout.addWidget(dropLineEdit, 1, 1)    self.setLayout(layout)    self.setWindowTitle("Custom Drag and Drop")if __name__ == "__main__":  app = QApplication(sys.argv)  form = Form()  form.show()  app.exec_()