在 QFrame 内移动（拖动）一个 QLabel

Question

我需要能够在背景图像顶部的屏幕上显示控件。我已经完成了该任务，并且已经创建并显示了一个控件（显示图像的 QLabel）。现在我需要能够通过将标签拖动到我希望移动它的位置来移动标签，我已经遵循了几个关于在 pyqt 中拖动的教程，但我未能完成这项任务

这是我的代码。注意控件可以移动，但是当你移动它时，背景也会移动，当你放下它时，它会保持在原来的位置。我想要的是只移动控件（显示图像的 QLabel）并移动它只是在选项卡内拖动：

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

class CentralWidget(QFrame):
    def __init__(self, *args):
    super(CentralWidget, self).__init__(*args)
    self.setStyleSheet("background-image: url(logo.png);")
    self.setAcceptDrops(True)

    def dragEnterEvent(self, e):
        e.accept()

    def dropEvent(self, e):
        # get the relative position from the mime data
        mime = e.mimeData().text()
        x, y = map(int, mime.split(','))
        # move
        # so move the dragged button (i.e. event.source())
        e.source().move(e.pos()-QPoint(x, y))
        # set the drop action as Move
        e.setDropAction(Qt.MoveAction)
        # tell the QDrag we accepted it
        e.accept()

class Selector(QLabel):
    def mouseMoveEvent(self, e):
        if e.buttons() != Qt.LeftButton:
            return

        # write the relative cursor position to mime data
        mimeData = QMimeData()
        # simple string with 'x,y'
        mimeData.setText('%d,%d' % (e.x(), e.y()))

        # let's make it fancy. we'll show a "ghost" of the button as we drag
        # grab the button to a pixmap
        pixmap = QPixmap.grabWidget(self)

        # below makes the pixmap half transparent
        painter = QPainter(pixmap)
        painter.setCompositionMode(painter.CompositionMode_DestinationIn)
        painter.fillRect(pixmap.rect(), QColor(0, 0, 0, 127))
        painter.end()

        # make a QDrag
        drag = QDrag(self)
        # put our MimeData
        drag.setMimeData(mimeData)
        # set its Pixmap
        drag.setPixmap(pixmap)
        # shift the Pixmap so that it coincides with the cursor position
        drag.setHotSpot(e.pos())

        # start the drag operation
        # exec_ will return the accepted action from dropEvent
        if drag.exec_(Qt.MoveAction) == Qt.MoveAction:
            print 'moved'
        # else:
            # print 'copied'

    def mousePressEvent(self, e):
        QLabel.mousePressEvent(self,e)
        if e.button() == Qt.LeftButton:
            print 'press'


class fPrincipal(QMainWindow):
    def __init__(self, parent=None):
    # Call base class constructor
    QMainWindow.__init__(self, parent)

    self.setGeometry(QRect(0, 0, 599+10, 399+10))
    self.move(QDesktopWidget().availableGeometry().center() - self.frameGeometry().center())

    # Creamos el contenedor central, que sera organizado por pestañas
    centralWidget = QTabWidget()
    self.setCentralWidget(centralWidget);

    # Creamos la 1ra pestaña
    tab = CentralWidget()

    tabLayout = QHBoxLayout()
    tab.setLayout(tabLayout)

    # Añadimos la pestaña al contenedor central
    centralWidget.addTab(tab,"Escena 1")

    logDockWidget = QDockWidget("Tools", self)
    logDockWidget.setObjectName("LogDockWidget")
    logDockWidget.setAllowedAreas(Qt.LeftDockWidgetArea | Qt.RightDockWidgetArea)
    self.addDockWidget(Qt.RightDockWidgetArea, logDockWidget)

    def crearMenu():
        mimenu = self.menuBar().addMenu("&Archivo")

    crearMenu()
    selectorLb = Selector()
    picture = QPixmap('D:\Adrian\Tesis\Codigo\selector.png')
    selectorLb.setPixmap(picture)
    tabLayout.addWidget(selectorLb)     

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

    w = fPrincipal()
    w.show()

    sys.exit(app.exec_())

Answer 1

查看PyQt fridgemagnets example，这是一个简化版：

#!/usr/bin/env python
#-*- coding:utf-8 -*-

import sip
sip.setapi('QString', 2)

from PyQt4 import QtCore, QtGui

myMimeType = 'application/MyWindow'

class MyLabel(QtGui.QLabel):
    def __init__(self, parent):
        super(MyLabel, self).__init__(parent)

        self.setStyleSheet("""
            background-color: black;
            color: white;
            font: bold;
            padding: 6px;
            border-width: 2px;
            border-style: solid;
            border-radius: 16px;
            border-color: white;
        """)

    def mousePressEvent(self, event):
        itemData   = QtCore.QByteArray()
        dataStream = QtCore.QDataStream(itemData, QtCore.QIODevice.WriteOnly)
        dataStream.writeString(self.text())
        dataStream << QtCore.QPoint(event.pos() - self.rect().topLeft())

        mimeData = QtCore.QMimeData()
        mimeData.setData(myMimeType, itemData)
        mimeData.setText(self.text())

        drag = QtGui.QDrag(self)
        drag.setMimeData(mimeData)
        drag.setHotSpot(event.pos() - self.rect().topLeft())

        self.hide()

        if drag.exec_(QtCore.Qt.MoveAction | QtCore.Qt.CopyAction, QtCore.Qt.CopyAction) == QtCore.Qt.MoveAction:
            self.close()

        else:
            self.show()


class MyFrame(QtGui.QFrame):
    def __init__(self, parent=None):
        super(MyFrame, self).__init__(parent)

        self.setStyleSheet("""
            background-color: lightgray;
            border-width: 2px;
            border-style: solid;
            border-color: black;
            margin: 2px;
        """)

        y = 6
        for labelNumber in range(6):
            label = MyLabel(self)
            label.setText("Label #{0}".format(labelNumber))
            label.move(6, y)
            label.show()

            y += label.height() + 2

        self.setAcceptDrops(True)

    def dragEnterEvent(self, event):
        if event.mimeData().hasFormat(myMimeType):
            if event.source() in self.children():
                event.setDropAction(QtCore.Qt.MoveAction)
                event.accept()

            else:
                event.acceptProposedAction()

        else:
            event.ignore()

    def dropEvent(self, event):
        if event.mimeData().hasFormat(myMimeType):
            mime       = event.mimeData()
            itemData   = mime.data(myMimeType)
            dataStream = QtCore.QDataStream(itemData, QtCore.QIODevice.ReadOnly)

            text = QtCore.QByteArray()
            offset = QtCore.QPoint()
            dataStream >> text >> offset

            newLabel = MyLabel(self)
            newLabel.setText(event.mimeData().text())
            newLabel.move(event.pos() - offset)
            newLabel.show()

            if event.source() in self.children():
                event.setDropAction(QtCore.Qt.MoveAction)
                event.accept()

            else:
                event.acceptProposedAction()

        else:
            event.ignore()

class MyWindow(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MyWindow, self).__init__(parent)

        self.myFrame = MyFrame(self)

        self.setCentralWidget(self.myFrame)

if __name__ == "__main__":
    import sys

    app = QtGui.QApplication(sys.argv)
    app.setApplicationName('MyWindow')

    main = MyWindow()
    main.resize(333, 333)
    main.move(app.desktop().screen().rect().center() - main.rect().center())
    main.show()

    sys.exit(app.exec_())