布局更改时调整QGraphicsScene的大小

Question

我在PySide2中使用了QGraphicsScene，我想在调整场景大小时调整其内容的大小。我可以在调整主窗口大小时触发调整大小，但是我不知道当窗口内容更改时如何触发大小调整。

这是一个小示例，其中有一个图形场景和两个按钮。在场景中是一个仅应触摸边缘的圆。当我单击其中一个按钮时，它显示或隐藏了另一个按钮。

import sys

from PySide2.QtGui import QResizeEvent
from PySide2.QtWidgets import (QPushButton, QApplication, QVBoxLayout, QDialog,
                               QSizePolicy, QGraphicsScene, QGraphicsView)


class Form(QDialog):

    def __init__(self, parent=None):
        super(Form, self).__init__(parent)
        # Create widgets
        self.scene = QGraphicsScene()
        self.circle = self.scene.addEllipse(0, 0, 10, 10)
        self.extra = QGraphicsView(self.scene)
        self.extra.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.Expanding)
        self.button1 = QPushButton("Button 1")
        self.button2 = QPushButton("Button 2")
        # Create layout and add widgets
        layout = QVBoxLayout()
        layout.addWidget(self.extra)
        layout.addWidget(self.button1)
        layout.addWidget(self.button2)
        # Set dialog layout
        self.setLayout(layout)
        # Add button signal to greetings slot
        self.button1.clicked.connect(self.on_click1)
        self.button2.clicked.connect(self.on_click2)

    def on_click1(self):
        self.button2.setVisible(not self.button2.isVisible())
        self.resizeEvent()

    def on_click2(self):
        self.button1.setVisible(not self.button1.isVisible())
        self.resizeEvent()

    def resizeEvent(self, event: QResizeEvent = None):
        size = self.extra.maximumViewportSize()
        target_size = min(size.width(), size.height()) - 1
        self.circle.setRect((size.width() - target_size) // 2,
                            (size.height() - target_size) // 2,
                            target_size,
                            target_size)
        self.extra.scene().setSceneRect(0, 0, size.width(), size.height())


if __name__ == '__main__':
    # Create the Qt Application
    app = QApplication(sys.argv)
    # Create and show the form
    form = Form()
    form.show()
    # Run the main Qt loop
    sys.exit(app.exec_())

当调整主窗口的大小以及按钮之一消失或重新出现时，将调整场景的大小。当主窗口调整大小时，圆圈会调整其大小，但按钮更改时不会调整。

当按钮更改时，如何处理调整大小？我想让圆圈在调整大小时仅碰触显示器的边缘。

Answer 1

问题是我正在处理主窗口的调整大小，而不是图形视图。创建一个QGraphicsView的新子类，并在那里处理resize事件。它将同时捕获两种调整大小事件。

import sys

from PySide2.QtGui import QResizeEvent
from PySide2.QtWidgets import (QPushButton, QApplication, QVBoxLayout, QDialog,
                               QSizePolicy, QGraphicsScene, QGraphicsView, QWidget)


class ResizingView(QGraphicsView):
    def __init__(self, parent: QWidget = None):
        super().__init__(parent)
        self.setScene(QGraphicsScene())
        self.circle = self.scene().addEllipse(0, 0, 1, 1)

    def resizeEvent(self, event: QResizeEvent):
        super().resizeEvent(event)
        size = event.size()
        target_size = min(size.width(), size.height()) - 1
        x = (size.width() - target_size) // 2
        y = (size.height() - target_size) // 2
        self.circle.setRect(x, y, target_size, target_size)
        self.setSceneRect(0, 0, size.width(), size.height())


class Form(QDialog):

    def __init__(self, parent=None):
        super(Form, self).__init__(parent)
        # Create widgets
        self.extra = ResizingView()
        self.extra.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.Expanding)
        self.button1 = QPushButton("Button 1")
        self.button2 = QPushButton("Button 2")
        # Create layout and add widgets
        layout = QVBoxLayout()
        layout.addWidget(self.extra)
        layout.addWidget(self.button1)
        layout.addWidget(self.button2)
        # Set dialog layout
        self.setLayout(layout)
        # Add button signal to greetings slot
        self.button1.clicked.connect(self.on_click1)
        self.button2.clicked.connect(self.on_click2)

    def on_click1(self):
        self.button2.setVisible(not self.button2.isVisible())

    def on_click2(self):
        self.button1.setVisible(not self.button1.isVisible())


if __name__ == '__main__':
    # Create the Qt Application
    app = QApplication(sys.argv)
    # Create and show the form
    form = Form()
    form.show()
    # Run the main Qt loop
    sys.exit(app.exec_())

如果您不想将所有调整大小逻辑都移到图形视图中，请在您的子类上创建一个新信号，并将其连接到应该处理调整大小事件的任何类上的插槽。如果仍然无法解决问题，请检查您是否在图形视图上调用setSceneRect()。

如果您不喜欢重新计算所有内容的大小，则可能更喜欢使用fitInView() method缩放所有内容的简单方法。这当然更容易，但是我更喜欢使用完整的尺寸计算集可以得到的更好的控制。这是使用fitInView()的示例。

import sys

from PySide2.QtCore import Qt
from PySide2.QtGui import QResizeEvent, QColor
from PySide2.QtWidgets import (QPushButton, QApplication, QVBoxLayout, QDialog,
                               QSizePolicy, QGraphicsScene, QGraphicsView, QWidget)


class ResizingView(QGraphicsView):
    def __init__(self, parent: QWidget = None):
        super().__init__(scene=QGraphicsScene(), parent=parent)
        self.circle = self.scene().addEllipse(1, 1, 98, 98)
        self.scene().addSimpleText('Centre').setPos(50, 50)
        self.scene().setBackgroundBrush(QColor('green'))
        self.scene().setSceneRect(0, 0, 100, 100)

    def resizeEvent(self, event: QResizeEvent):
        self.fitInView(0, 0, 100, 100, Qt.KeepAspectRatio)
        super().resizeEvent(event)


class Form(QDialog):

    def __init__(self, parent=None):
        super(Form, self).__init__(parent)
        # Create widgets
        self.extra = ResizingView()
        self.extra.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.Expanding)
        self.button1 = QPushButton("Button 1")
        self.button2 = QPushButton("Button 2")
        # Create layout and add widgets
        layout = QVBoxLayout()
        layout.addWidget(self.extra)
        layout.addWidget(self.button1)
        layout.addWidget(self.button2)
        # Set dialog layout
        self.setLayout(layout)
        # Add button signal to greetings slot
        self.button1.clicked.connect(self.on_click1)
        self.button2.clicked.connect(self.on_click2)

    def on_click1(self):
        self.button2.setVisible(not self.button2.isVisible())

    def on_click2(self):
        self.button1.setVisible(not self.button1.isVisible())


if __name__ == '__main__':
    # Create the Qt Application
    app = QApplication(sys.argv)
    # Create and show the form
    form = Form()
    form.show()
    # Run the main Qt loop
    sys.exit(app.exec_())

无论哪种方式，关键是要继承QGraphicsView的子类并处理其resizeEvent()而不是主表单中的那个。