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BrainSwitch
Asked:2020-11-23 14:30:11 +0000 UTC2020-11-23 14:30:11 +0000 UTC

在 QGraphicsScene 中绘制动态矩形

  • 772

在应用程序窗口中，应根据在桌面上选择东西时如何形成矩形的原理，用鼠标绘制一个矩形。

问题是矩形被绘制在错误的位置。

我还想在移动鼠标光标时更改矩形的大小，而不是mouseMoveEvent在每个事件上删除并创建一个矩形。

编码：

import sys

from PyQt5.QtWidgets import QWidget, QVBoxLayout, QGraphicsScene, QGraphicsView, QApplication


class CustomGraphicsView(QGraphicsView):
    def __init__(self, scene):
        super().__init__(scene)
        self.x = 0
        self.y = 0
        self.rect = None

    def mousePressEvent(self, QMouseEvent):
        self.x = QMouseEvent.pos().x()
        self.y =  QMouseEvent.pos().y()

    def mouseMoveEvent(self, QMouseEvent):
        new_x = QMouseEvent.pos().x()
        new_y =  QMouseEvent.pos().y()
        if self.rect != None:
            self.scene().removeItem(self.rect)
        self.rect = self.scene().addRect(self.x, self.y,  new_x - self.x, new_y - self.y)

    def mouseReleaseEvent(self, QMouseEvent):
        self.scene().removeItem(self.rect)


class MainWindow(QWidget):
    def __init__(self):
        super().__init__()
        self.init_UI()

    def init_UI(self):
        vbox = QVBoxLayout()
        self.setLayout(vbox)
        self.graphics_scene = QGraphicsScene(self)
        graphics_view = CustomGraphicsView(self.graphics_scene)
        vbox.addWidget(graphics_view)


if __name__ == '__main__':
    application = QApplication(sys.argv)
    main_window = MainWindow()
    main_window.setGeometry(100,100,600,600)
    main_window.show()

    sys.exit(application.exec_())
python

2 个回答

  1. Best Answer

    作为一种选择：

    import sys
from PyQt5.QtWidgets import (QWidget, QVBoxLayout, QGraphicsScene, QGraphicsView, 
                             QMainWindow, QApplication, QGraphicsRectItem, QGraphicsItem)
from PyQt5.QtCore    import QRectF, QPointF, Qt
from PyQt5.QtGui     import QTransform

class GraphicsScene(QGraphicsScene):
    def __init__(self, parent=None):
        super(GraphicsScene, self).__init__(QRectF(-500, -500, 1000, 1000), parent)

        self._start = QPointF()
        self._current_rect_item = None

    def mousePressEvent(self, event):
        if self.itemAt(event.scenePos(), QTransform()) is None:
            self._current_rect_item = QGraphicsRectItem()
            self._current_rect_item.setBrush(Qt.blue)  
            self._current_rect_item.setFlag(QGraphicsItem.ItemIsMovable, True)
            self.addItem(self._current_rect_item)
            self._start = event.scenePos()
            r = QRectF(self._start, self._start)
            self._current_rect_item.setRect(r)
        super(GraphicsScene, self).mousePressEvent(event)

    def mouseMoveEvent(self, event):
        if self._current_rect_item is not None:
            r = QRectF(self._start, event.scenePos()).normalized()
            self._current_rect_item.setRect(r)
        super(GraphicsScene, self).mouseMoveEvent(event)

    def mouseReleaseEvent(self, event):
        self._current_rect_item = None
        super(GraphicsScene, self).mouseReleaseEvent(event)

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

        scene = GraphicsScene(self)
        view  = QGraphicsView(scene)
        self.setCentralWidget(view)

if __name__ == '__main__':
    application = QApplication(sys.argv)
    main_window = MainWindow()
    main_window.setGeometry(100,100,600,600)
    main_window.show()
    sys.exit(application.exec_())

    在此处输入图像描述

    • 2

  2. 单击鼠标按钮时突出显示+释放时消失：

    from PyQt5.QtWidgets import (
    QGraphicsScene, QGraphicsView, QMainWindow, QApplication, QGraphicsRectItem
)
from PyQt5.QtCore import QRectF, QPointF
from PyQt5.QtGui import QColor, QPainter

class GraphicsScene(QGraphicsScene):
    def __init__(self):
        super().__init__()

        self._pos = QPointF()
        self._current_item = None

        # Полупрозрачный цвет
        self._item_color = QColor(0, 0, 255, 128)

    def mousePressEvent(self, event):
        super().mousePressEvent(event)

        self._pos = event.scenePos()

        self._current_item = QGraphicsRectItem()
        self._current_item.setBrush(self._item_color)

        self.addItem(self._current_item)
        self._current_item.setRect(QRectF(self._pos, self._pos))

    def mouseMoveEvent(self, event):
        super().mouseMoveEvent(event)

        if self._current_item:
            rect = QRectF(self._pos, event.scenePos()).normalized()
            self._current_item.setRect(rect)

    def mouseReleaseEvent(self, event):
        super().mouseReleaseEvent(event)

        # Убираем после отпускания кнопки мыши
        self.removeItem(self._current_item)
        self._current_item = None


class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        scene_rect = QRectF(0, 0, 500, 500)

        self.scene = GraphicsScene()

        self.view = QGraphicsView(self.scene)
        self.view.setRenderHint(QPainter.Antialiasing)
        self.view.setSceneRect(scene_rect)

        self.scene.addRect(0, 0, 200, 100)
        self.scene.addEllipse(100, 50, 200, 200)
        self.scene.addText("Hello World!").setPos(300, 300)

        self.setCentralWidget(self.view)


if __name__ == '__main__':
    app = QApplication([])

    mw = MainWindow()
    mw.resize(600, 600)
    mw.show()

    app.exec()

    截屏：

    在此处输入图像描述

    • 2

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