为什么我不能在图形视图上使用鼠标事件（mouseMoveEvent，mouseReleaseEvent）？

Question

我想用python和pyqt5制作裁剪图像工具

下面的代码，我不能使用 mouseMoveEvent 和 mouseReleaseEvent on 图形视图。

但是，我只能在图形视图上使用 mousePressEvent。我检查了有关 QGraphicView 属性的交互。

import sys
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from PIL import Image
from PyQt5 import uic

QApplication.setAttribute(Qt.AA_EnableHighDpiScaling, True)

IS_RESULT = False

CROP_UI = uic.loadUiType("Image_crop_screen.ui")[0]
BRING_IN_IMG_ROUTE = "C:/Users/yoon/Desktop/test/test.jpg"

class MainScreen(QMainWindow, CROP_UI):
    def __init__(self):

        super().__init__()
        self.setupUi(self)

        # Graphic Screen set
        self.img = QGraphicsPixmapItem(QPixmap(BRING_IN_IMG_ROUTE))
        self.scene = QGraphicsScene()

        self.scene.addItem(self.img)
        self.graphicsView.setScene(self.scene)

        self.graphicsView.pencolor = QColor(240, 240, 240)
        self.graphicsView.brushcolor = QColor(255, 255, 255, 0)

        QGV = QGraphicsView()

        self.items = []

        # Full Screen set size
        _WIDTH_ADD = 25
        _HEIGHT_ADD = 25
        self.setGeometry(0, 0, 640 + _WIDTH_ADD, 500 + _HEIGHT_ADD)


    def moveEvent(self, e):

        rect = QRectF(self.rect())
        rect.adjust(0, 0, 0, 0)  # 창 스크롤 바 없애기 위해서 일부 크기 작게 설정

        self.scene.setSceneRect(rect)

    # Draw rectangular while moving mouse
    def mouseMoveEvent(self, e):
        # e.buttons()는 정수형 값을 리턴, e.button()은 move시 Qt.Nobutton 리턴
        print(Qt.LeftButton)
        print(e.buttons())
        print(e)


        if e.buttons() & Qt.LeftButton:
            self.end = e.pos()
            pen = QPen(self.parent().pencolor)
            brush = QBrush(self.parent().brushcolor)
            pen.setWidth(3)

            # 장면에 그려진 이전 선을 제거
            if len(self.items) > 0:
                self.scene.removeItem(self.items[-1])
                del (self.items[-1])

            rect = QRectF(self.start, self.end)
            self.items.append(self.scene.addRect(rect, pen, brush))

    def mousePressEvent(self, e):
        if e.button() == Qt.LeftButton:
            # 시작점 저장
            self.start = e.pos()
            self.end = e.pos()

            print(Qt.LeftButton)
            print(e.buttons())
            print(e)

    def mouseReleaseEvent(self, e):
        print("aaa2")

        if e.button() == Qt.LeftButton:
            global IS_RESULT

            print("ttt2")

            pen = QPen(self.parent().pencolor)
            brush = QBrush(self.parent().brushcolor)

            self.items.clear()
            rect = QRectF(self.start, self.end)
            self.scene.addRect(rect, pen, brush)

            print("(" + str(self.start.x()) + ", " + str(self.start.y()) + "), (" + str(self.end.x()) + ", " + str(
                self.end.y()) + ")")
            area = (self.start.x(), self.start.y(), self.end.x(), self.end.y())



if __name__ == '__main__':
    app = QApplication(sys.argv)
    w = MainScreen()
    w.show()

    sys.exit(app.exec_())

Answer 1

如果您想监听 QGraphicsView 的事件，则不应覆盖另一个小部件的事件，因为某些事件不会被传输。在这种情况下最好使用跟踪鼠标的事件过滤器，在这种情况下应该监控 QGraphicsView 的 viewport() 的事件。

在下面的示例中，我将展示如何使用鼠标创建矩形。

class MainScreen(QMainWindow, CROP_UI):
    def __init__(self):

        super().__init__()
        self.setupUi(self)

        # Graphic Screen set
        self.img = QGraphicsPixmapItem(QPixmap(BRING_IN_IMG_ROUTE))
        self.scene = QGraphicsScene()
        self.scene.addItem(self.img)
        self.graphicsView.setScene(self.scene)

        # Full Screen set size
        _WIDTH_ADD = 25
        _HEIGHT_ADD = 25
        self.setGeometry(0, 0, 640 + _WIDTH_ADD, 500 + _HEIGHT_ADD)

        self.graphicsView.viewport().installEventFilter(self)

        self.current_item = None
        self.start_pos = QPointF()
        self.end_pos = QPointF()

    def eventFilter(self, o, e):
        if self.graphicsView.viewport() is o:
            if e.type() == QEvent.MouseButtonPress:
                if e.buttons() & Qt.LeftButton:
                    print("press")
                    self.start_pos = self.end_pos = self.graphicsView.mapToScene(
                        e.pos()
                    )
                    pen = QPen(QColor(240, 240, 240))
                    pen.setWidth(3)
                    brush = QBrush(QColor(100, 255, 100, 100))
                    self.current_item = self.scene.addRect(QRectF(), pen, brush)
                    self._update_item()
            elif e.type() == QEvent.MouseMove:
                if e.buttons() & Qt.LeftButton and self.current_item is not None:
                    print("move")
                    self.end_pos = self.graphicsView.mapToScene(e.pos())
                    self._update_item()
            elif e.type() == QEvent.MouseButtonRelease:
                print("release")
                self.end_pos = self.graphicsView.mapToScene(e.pos())
                self._update_item()
                self.current_item = None

        return super().eventFilter(o, e)

    def _update_item(self):
        if self.current_item is not None:
            self.current_item.setRect(QRectF(self.start_pos, self.end_pos).normalized())

Answer 2

您必须创建一个类型为 QGraphicView 的类，您将在其中使用鼠标事件

class MyGraphicView(QGraphicsView):
   def __init__():
      super.__init__(self)
      self.myScene = QGraphicsScene()
      self.setScene(self.myScene)
      # the rest code

   def mousePressEvent(self, event):
      ...
   def mouseMoveEvent(self, event):
      ...
   def mouseReleaseEvent(self, event):
      ...