如何从 QMainWindow 绘制 QGraphicsView

Question

下面显示的 QgraphicsView 和 QMainWindow 的当前设计 class 是我在不同软件中的设计示例。

我必须向 QGraphicsView 添加滚动条。原版软件所有的鼠标事件都在QMainWindow中处理。

问题：通过QMainWindow在QGraphicsView上绘图的方法是什么？

import sys

from PyQt4 import QtGui
from PyQt4 import QtCore

class Window(QtGui.QGraphicsView):

  def __init__(self, parent=None):

        QtGui.QGraphicsView.__init__(self, parent)
        self.scene = QtGui.QGraphicsScene(self)
        self.scene.setBackgroundBrush(QtGui.QBrush(QtCore.Qt.darkGray, QtCore.Qt.SolidPattern))
        self.setScene(self.scene)

        #self.setDragMode(QtGui.QGraphicsView.ScrollHandDrag)
        self.setTransformationAnchor(QtGui.QGraphicsView.AnchorUnderMouse)
        #self.viewport().setCursor(QtCore.Qt.CrossCursor)
        self.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)
        self.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)

        print "sdsads"


  def mousePressEvent(self, ev):
        item = QtGui.QGraphicsTextItem("")
        item.setPos(ev.x(), ev.y())
        self.scene.addItem(item)

        print "ev.x() ", ev.x()


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

        QtGui.QMainWindow.__init__(self, parent)
        centralwidget = Window()
        self.setCentralWidget(centralwidget) 

        centralwidget.scene.addPixmap(QtGui.QPixmap("exit.png"))



app = QtGui.QApplication(sys.argv)
GUI = CityscapesLabelTool()
GUI.show()
sys.exit(app.exec_())

Answer 1

在QGraphicsView中，向场景中添加项目是正常的，例如，如果你想绘制一个多边形，你必须使用QGraphicsPolygonItem，如果你想获得正确的点，你必须使用 QGraphicsScene 而不是 QGraphicsView.

在下面的示例中，您可以通过单击鼠标左键指定多边形点，然后单击鼠标右键完成绘制。

import sys

from PyQt4 import QtCore, QtGui

class GraphicsScene(QtGui.QGraphicsScene):
    def __init__(self, *args, **kwargs):
        QtGui.QGraphicsScene.__init__(self, *args, **kwargs)
        self.polygon = None

    def mousePressEvent(self, ev):
        if ev.button() == QtCore.Qt.RightButton:
            self.polygon << ev.scenePos()
            item = QtGui.QGraphicsPolygonItem(self.polygon)
            item.setPen(QtGui.QPen(QtCore.Qt.red))
            item.setBrush(QtGui.QBrush(QtCore.Qt.red))
            self.addItem(item)
            # or
            # self.addPolygon(self.polygon, QtGui.QPen(QtCore.Qt.red), QtGui.QBrush(QtCore.Qt.red))
            self.polygon = None

        else:
            if self.polygon is None:
                self.polygon = QtGui.QPolygonF()
            self.polygon << ev.scenePos()

class Window(QtGui.QGraphicsView):
    def __init__(self, parent=None):
        QtGui.QGraphicsView.__init__(self, parent)
        self.scene =GraphicsScene(QtCore.QRectF(0, 0, 640, 480), self)
        self.scene.setBackgroundBrush(QtGui.QBrush(QtCore.Qt.darkGray, QtCore.Qt.SolidPattern))
        self.setScene(self.scene)
        #self.setDragMode(QtGui.QGraphicsView.ScrollHandDrag)
        self.setTransformationAnchor(QtGui.QGraphicsView.AnchorUnderMouse)
        #self.viewport().setCursor(QtCore.Qt.CrossCursor)
        self.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)
        self.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)


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

        QtGui.QMainWindow.__init__(self, parent)
        centralwidget = Window()
        self.setCentralWidget(centralwidget) 

        centralwidget.scene.addPixmap(QtGui.QPixmap("exit.png"))


app = QtGui.QApplication(sys.argv)
GUI = CityscapesLabelTool()
GUI.show()
sys.exit(app.exec_())

输出：

你有一个 XY problem，你正在寻找主要问题的解决方案，但不知道它是正确的，根据你的评论，你的主要问题是添加 QScrollBar 到 QMainWindow，在那个元素中你想画图，所以没有必要使用 QGraphicsView 而是 QScrollArea.

import sys

from PyQt4 import QtCore, QtGui


class Window(QtGui.QWidget):
    def __init__(self, parent=None):
        QtGui.QWidget.__init__(self, parent)
        self.polygon = None
        self.setFixedSize(640, 480)
        self.pixmap = None

    def mousePressEvent(self, ev):
        if self.polygon is None:
            self.polygon = QtGui.QPolygon()
        self.polygon << ev.pos()
        self.update()

    def paintEvent(self, ev):
        painter = QtGui.QPainter(self)
        painter.fillRect(self.rect(), QtGui.QBrush(QtCore.Qt.darkGray, QtCore.Qt.SolidPattern))
        painter.drawPixmap(QtCore.QPoint(0, 0), QtGui.QPixmap("exit.png"))
        if self.polygon is not None:
            painter.setPen(QtCore.Qt.blue)
            painter.drawPolyline(self.polygon)



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

        QtGui.QMainWindow.__init__(self, parent)
        scroll = QtGui.QScrollArea()

        scroll.setBackgroundRole(QtGui.QPalette.Dark)
        scroll.setWidget(Window())
        scroll.setWidgetResizable(True)
        self.setCentralWidget(scroll)



app = QtGui.QApplication(sys.argv)
GUI = CityscapesLabelTool()
GUI.show()
sys.exit(app.exec_())

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