Python 在QgraphicsView中拖放'；t工作（PyQt）

我为一些按钮创建了一个自定义类。这些是一个“可拖动”按钮，其名称表明，这些按钮可以相互拖放（取决于是否设置了allowDrag属性），然后执行操作。 这些拖拽按钮的代码已发布在此处：

显然，当按钮在QWidget中时效果很好，但是当它们被添加到QGraphicsView的场景中时（我也制作了一个自定义类），drop事件就不起作用了。我得到了一个

QGraphicsItem:：ungrabMouse:而不是一个鼠标抓取器

警告

这是自定义图形视图的代码：

from PyQt4 import QtGui, QtCore

class WiringGraphicsView(QtGui.QGraphicsView):
    #Initializer method
    def __init__(self, parent = None,  scene=None):
        QtGui.QGraphicsView.__init__(self, scene, parent)
    #Set Accept Drops property true
        self.setAcceptDrops(True)

    #This method creates a line between two widgets
    def paintWire(self, start_widget,  end_widget):
        #Size and Position of both widgets
        _start = start_widget.geometry()
        _end = end_widget.geometry()
        #Creates a Brush object with Red color 
        brush = QtGui.QBrush(QtGui.QColor(255, 0, 0) )
        #Creates Pen object with specified brush
        pen = QtGui.QPen(brush, 2)
        #Create a Line object between two widgets
        line = QtGui.QGraphicsLineItem(_start.x() + _start.width() / 2, _start.y() + _start.height() / 2, _end.x() + _end.width() / 2, _end.y() + _end.height() / 2)
        #Set the Pen for the Line
        line.setPen(pen)
        #Add this line item to the scene.
        self.scene().addItem( line )

这里是自定义按钮和图形视图所在的代码：

from PyQt4.QtGui import *
from PyQt4.QtCore import *
from dragbutton import DragButton
from wiringgraphicsview import WiringGraphicsView
import icons_rc

app = QApplication([])

scene = QGraphicsScene()

menu = QMenu()

# put a button into the scene and move it
button1 = DragButton('Button 1')
button1.setText("")
button1.setDefault(False)
button1.setAutoDefault(True)
#button1.setMouseTracking(True)
button1.setAllowDrag(True) #Allow Drag n Drop of DragButton
button1.setGeometry(QRect(50, 50, 51, 31)) #Set dimensions of it
#Set icon of button1
icon = QIcon()
icon.addPixmap(QPixmap(":/audio-input-line.png"), QIcon.Normal, QIcon.Off)
button1.setIcon(icon)
button1.setFlat(True)
button1.setMenu(menu)
#Create a QGraphicsProxyWidget adding the widget to scene
scene_button1 = scene.addWidget(button1)
#move the button on the scene
r1 = scene_button1.geometry()
r1.moveTo(-100, -50)

# put another button into the scene
button2 = DragButton('Button 2')
button2.setText("")
#This button shoudn't be dragged, it is just for dropping.
button2.setAllowDrag(False)
button2.setAcceptDrops(True)
icon = QIcon()
icon.addPixmap(QPixmap(":/input_small.png"), QIcon.Normal, QIcon.Off)
button2.setIcon(icon)
#button2.setMouseTracking(True)
#button2.setGeometry(QRect(270, 150, 41, 31))
scene_button2 = scene.addWidget(button2)
scene_button2.setAcceptDrops(True)
r2 = scene_button2.geometry()

# Create the view using the scene
view = WiringGraphicsView(None, scene)
view.resize(300, 200)
view.show()
#and paint a wire between those buttons
view.paintWire(button1, button2)
app.exec_()

另外：如果我想先将按钮嵌入到水平或垂直布局中（使其有序），然后再嵌入到QgraphicsView中，那会怎么样呢

编辑：我已经发现，可以像其他小部件一样，将布局及其子按钮添加到图形场景中。 我仍然不知道为什么我在dragbutton类中实现的drag n drop在QGraphicscene/QgraphicsView中不起作用。 我读过的大多数文档都谈到实现拖放逻辑，但都是在QgraphicsItem类中实现的。 基于QGraphicsItem创建一个新类是一个好主意，但此时我要回答以下问题：

• 我想如何重新实现按钮行为？单击“效果”、“属性”和添加QMenu的可能性？当我使用

  addWidget

  将QButton或自定义拖动按钮添加到场景中时，这已经起作用了
• 布局如何？我无法将QgraphicsItem添加到布局中，然后再将布局添加到场景中！当这些项目位于场景/视图中时，是否有方法将其按顺序排列

编辑2：我在另一篇文章中包含了“DragButton”类的代码，因为它与这个问题相关

from PyQt4 import QtGui, QtCore

class DragButton(QtGui.QPushButton):

def __init__(self, parent):
     super(DragButton,  self).__init__(parent)
     self.allowDrag = True

def setAllowDrag(self, allowDrag):
    if type(allowDrag) == bool:
       self.allowDrag = allowDrag
    else:
        raise TypeError("You have to set a boolean type")

def mouseMoveEvent(self, e):
    if e.buttons() != QtCore.Qt.RightButton:
        return

    if self.allowDrag == True:
        # write the relative cursor position to mime data
        mimeData = QtCore.QMimeData()
        # simple string with 'x,y'
        mimeData.setText('%d,%d' % (e.x(), e.y()))
        print mimeData.text()

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

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

        # make a QDrag
        drag = QtGui.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_(QtCore.Qt.LinkAction | QtCore.Qt.MoveAction) == QtCore.Qt.LinkAction:
            print 'linked'
        else:
            print 'moved'

def mousePressEvent(self, e):
    QtGui.QPushButton.mousePressEvent(self, e)
    if e.button() == QtCore.Qt.LeftButton:
        print 'press'
        #AQUI DEBO IMPLEMENTAR EL MENU CONTEXTUAL

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())
    print e.pos()
        #e.source().move(e.pos()-QtCore.QPoint(x, y))
        # set the drop action as LinkAction
    e.setDropAction(QtCore.Qt.LinkAction)
    # tell the QDrag we accepted it
    e.accept()

---

该解决方案似乎需要子类

qgraphicscene

将放置事件显式传递到放置坐标处的

QGraphicsItem

。此外，

QGraphicsProxyWidget

似乎不会将放置事件传递给子小部件。同样，您需要子类化

QGraphicsProxyWidget

并手动实例化这个类，添加小部件，然后使用

scene.addItem（）

将实例手动添加到场景中

注意：您可能知道，但是您必须先与小部件交互（例如，单击它），才能开始拖放。大概这可以通过将

mouseMoveEvent

从场景传递到代理，然后传递到小部件来解决

注2：我不知道为什么要花这么多的精力才能做到这一点。我确实觉得我可能错过了什么。报告说：

QGraphicsProxyWidget支持QWidget的所有核心功能，包括选项卡焦点、键盘输入、拖放和弹出窗口

但是如果没有子类化，我就无法使它工作

相关子类实现：

class MyScene(QGraphicsScene):
    def dragEnterEvent(self, e):
        e.acceptProposedAction()

    def dropEvent(self, e):
        # find item at these coordinates
        item = self.itemAt(e.scenePos())
        if item.setAcceptDrops == True: 
            # pass on event to item at the coordinates
            try:
               item.dropEvent(e)
            except RuntimeError: 
                pass #This will supress a Runtime Error generated when dropping into a widget with no MyProxy        

    def dragMoveEvent(self, e):
        e.acceptProposedAction()

class MyProxy(QGraphicsProxyWidget):    
    def dragEnterEvent(self, e):
        e.acceptProposedAction()

    def dropEvent(self, e):
        # pass drop event to child widget
        return self.widget().dropEvent(e)        

    def dragMoveEvent(self, e):
        e.acceptProposedAction()

修改的应用程序代码：

scene = MyScene()
...
my_proxy = MyProxy()
my_proxy.setWidget(button2)
my_proxy.setAcceptDrops(True)
scene.addItem(my_proxy)
...

完全工作（好吧，当拖放成功时，它会打印出“链接”…这是您之前编写的所有操作）应用程序：

from PyQt4 import QtGui, QtCore

class WiringGraphicsView(QtGui.QGraphicsView):
    #Initializer method
    def __init__(self, parent = None,  scene=None):
        QtGui.QGraphicsView.__init__(self, scene, parent)
    #Set Accept Drops property true
        self.setAcceptDrops(True)

    #This method creates a line between two widgets
    def paintWire(self, start_widget,  end_widget):
        #Size and Position of both widgets
        _start = start_widget.geometry()
        _end = end_widget.geometry()
        #Creates a Brush object with Red color 
        brush = QtGui.QBrush(QtGui.QColor(255, 0, 0) )
        #Creates Pen object with specified brush
        pen = QtGui.QPen(brush, 2)
        #Create a Line object between two widgets
        line = QtGui.QGraphicsLineItem(_start.x() + _start.width() / 2, _start.y() + _start.height() / 2, _end.x() + _end.width() / 2, _end.y() + _end.height() / 2)
        #Set the Pen for the Line
        line.setPen(pen)
        #Add this line item to the scene.
        self.scene().addItem( line )

class DragButton(QtGui.QPushButton):
    def __init__(self, parent):
         super(DragButton,  self).__init__(parent)
         self.allowDrag = True

    def setAllowDrag(self, allowDrag):
        if type(allowDrag) == bool:
           self.allowDrag = allowDrag
        else:
            raise TypeError("You have to set a boolean type")

    def mouseMoveEvent(self, e):
        if e.buttons() != QtCore.Qt.RightButton:
            return QtGui.QPushButton.mouseMoveEvent(self, e)

        if self.allowDrag == True:
            # write the relative cursor position to mime data
            mimeData = QtCore.QMimeData()
            # simple string with 'x,y'
            mimeData.setText('%d,%d' % (e.x(), e.y()))
            # print mimeData.text()

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

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

            # make a QDrag
            drag = QtGui.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_(QtCore.Qt.LinkAction | QtCore.Qt.MoveAction) == QtCore.Qt.LinkAction:
                print 'linked'
            else:
                print 'moved'

        return QtGui.QPushButton.mouseMoveEvent(self, e)

    def mousePressEvent(self, e):

        if e.button() == QtCore.Qt.LeftButton:
            print 'press'
            #AQUI DEBO IMPLEMENTAR EL MENU CONTEXTUAL
        return QtGui.QPushButton.mousePressEvent(self, e)

    def dragEnterEvent(self, e):
        e.accept()
        return QtGui.QPushButton.dragEnterEvent(self, e)

    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())
        print e.pos()
        # e.source().move(e.pos()-QtCore.QPoint(x, y))
            # set the drop action as LinkAction
        e.setDropAction(QtCore.Qt.LinkAction)
        # tell the QDrag we accepted it
        e.accept()

        return QtGui.QPushButton.dropEvent(self, QDropEvent(QPoint(e.pos().x(), e.pos().y()), e.possibleActions(), e.mimeData(), e.buttons(), e.modifiers()))



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

class MyScene(QGraphicsScene):
    def dragEnterEvent(self, e):
        e.acceptProposedAction()

    def dropEvent(self, e):
    # find item at these coordinates
    item = self.itemAt(e.scenePos())
    if item.setAcceptDrops == True:
        # pass on event to item at the coordinates
        try:
           item.dropEvent(e)
        except RuntimeError: 
            pass #This will supress a Runtime Error generated when dropping into a widget with no ProxyWidget      

    def dragMoveEvent(self, e):
        e.acceptProposedAction()

class MyProxy(QGraphicsProxyWidget):    
    def dragEnterEvent(self, e):
        e.acceptProposedAction()

    def dropEvent(self, e):
        # pass drop event to child widget
        return self.widget().dropEvent(e)        

    def dragMoveEvent(self, e):
        e.acceptProposedAction()


app = QApplication([])

scene = MyScene()

menu = QMenu()

# put a button into the scene and move it
button1 = DragButton('Button 1')
button1.setText("aaa")
button1.setDefault(False)
button1.setAutoDefault(True)
#button1.setMouseTracking(True)
button1.setAllowDrag(True) #Allow Drag n Drop of DragButton
button1.setGeometry(QRect(50, 50, 51, 31)) #Set dimensions of it
#Set icon of button1
icon = QIcon()
icon.addPixmap(QPixmap(":/audio-input-line.png"), QIcon.Normal, QIcon.Off)
button1.setIcon(icon)
button1.setFlat(True)
button1.setMenu(menu)
#Create a QGraphicsProxyWidget adding the widget to scene
scene_button1 = scene.addWidget(button1)
#move the button on the scene
r1 = scene_button1.geometry()
r1.moveTo(-100, -50)

# put another button into the scene
button2 = DragButton('Button 2')
button2.setText("bbb")
#This button shoudn't be dragged, it is just for dropping.
button2.setAllowDrag(False)
button2.setAcceptDrops(True)
icon = QIcon()
icon.addPixmap(QPixmap(":/input_small.png"), QIcon.Normal, QIcon.Off)
button2.setIcon(icon)
#button2.setMouseTracking(True)
#button2.setGeometry(QRect(270, 150, 41, 31))

# Instantiate our own proxy which forwars drag/drop events to the child widget
my_proxy = MyProxy()
my_proxy.setWidget(button2)
my_proxy.setAcceptDrops(True)
scene.addItem(my_proxy)

# Create the view using the scene
view = WiringGraphicsView(None, scene)
view.resize(300, 200)
view.show()
#and paint a wire between those buttons
view.paintWire(button1, button2)
app.exec_()

---

我试图从所有这些代码片段中拼凑出一个示例，但我无法重现您看到的错误。我不能移动按钮，但它会在终端上打印“移动”和坐标。它不会打印您引用的错误。我不太确定你期望发生什么。您当前的代码中没有任何一个对移动QGraphicscene中的按钮有任何作用…@three_Pinepples至少它应该打印“linked”，并且光标应该在即将放下时改变。当它们在场景中时不会发生。你看到上面按钮代码的链接了吗？又来了：@three_Pinepples我为按钮添加了代码。正如我所说，当它们在布局或小部件中时，它们会按预期工作，但一旦它们被添加到GraphicsCenter中，显然就不起作用。您可以发布/链接到一个在qwidget模式下使用拖动按钮而不使用qgraphicsview/场景的可运行示例吗？这样我就能更好地理解它是如何工作的。@three_Pinepples在这里：我还读了一些关于QGraphicsProxyWidget的引文，这就是为什么我如此困惑的原因，因为我认为只要用

addWidget（）

将按钮添加到场景中就足以获得所有拖放行为。至少你的解决方案像预期的那样有效，谢谢。是的，我同意。我也会这么想。也许其他人会知道为什么…我在玩你的一些代码，我发现我可以像往常一样使用addWidget（）将带有布局和子按钮的QWidget添加到场景中，这很好，因为布局允许我对齐按钮，但这只会将它们带到场景中。正如我们所看到的，drag n drop不起作用，至少我为每个接收drop的按钮实例化了一个代理。所以我做了并且工作了。现在唯一困扰我的是一个异常

异常“unhandled RuntimeError”无法访问非Python创建的对象的受保护函数或信号
，每次我放入包含按钮的QWidget（但不是放在按钮上）时都会引发该异常。哦，我发现，每当我进入一个没有自己代理的对象时，这个值就会升高。