python - 在 PyQt5 中实现 Canvas

Question

我一直在尝试学习使用 PyQt5。

我想在“菜单栏”下方实现一个 Canvas

class gui(QDialog):
    def __init__(self, parent=None):
        super(gui, self).__init__(parent)
        self.createTopLayout()
        self.painter = canvas(self)
        mainLayout = QGridLayout()
        mainLayout.addLayout(self.topLayout, 0, 0, 1, 2)
        mainLayout.addWidget(self.painter, 1, 0, 6, 2)
        self.setLayout(mainLayout)

    def createTopLayout(self):
        self.topLayout = QHBoxLayout()
        button1 = QPushButton("b1")
        button2 = QPushButton("b2")
        button3 = QPushButton("b3")
        styleComboBox = QComboBox()
        styleComboBox.addItems(QStyleFactory.keys())
        styleLabel = QLabel("&Style:")
        styleLabel.setBuddy(styleComboBox)
        self.topLayout.addWidget(styleLabel)
        self.topLayout.addWidget(styleComboBox)
        self.topLayout.addStretch(1)
        self.topLayout.addWidget(button1)
        self.topLayout.addWidget(button2)
        self.topLayout.addWidget(button3)

我的 Canvas 定义为

class canvas(QMainWindow):
    def __init__(self, parent=None):
        super(canvas, self).__init__(parent)
        self.setGeometry(100, 100, 1000, 700)

    def paintEvent(self, e):
        cir = circle() #circle class creates a circle with random center and radius both between 0 to 100
        painter = QPainter(self)
        painter.setPen(QPen(Qt.red, 1, Qt.SolidLine))
        painter.drawEllipse(self, cir.center.x, cir.center.y, cir.radius, cir.radius)

但对我来说， Canvas 根本不渲染，更不用说椭圆了。

Answer 1

您不应该使用 QMainWindow 作为 Canvas ，而应使用 QWidget。另一方面，如果您使用布局，setGeometry 将不起作用，因为后者处理几何图形，而是建立固定的大小和足够的边距。另一方面，建议类的名称以大写字母开头，考虑到上述解决方案是:

class Canvas(<b>QWidget</b>):
    def __init__(self, parent=None):
        super(Canvas, self).__init__(parent)
        <b>self.setFixedSize(1000, 700)
        self.setContentsMargins(100, 100, 100, 100)</b>

    def paintEvent(self, e):
        # ...