pyqt5 - 调整 QWindow 的大小以适应内容

Question

我的 PyQt5 应用程序的主窗口在自定义画布小部件上方设置了一个文本标签，该小部件显示图像：

from PyQt5 import QtCore, QtGui, QtWidgets


class Canvas(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()
        self.image = None

    def paintEvent(self, event):
        qp = QtGui.QPainter(self)
        if self.image:
            qp.drawImage(0, 0, self.image)


class Window(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()

        self.canvas = Canvas()

        self.label = QtWidgets.QLabel()
        self.label.setText('foobar')
        self.label.setSizePolicy(QtWidgets.QSizePolicy.Expanding,
                                QtWidgets.QSizePolicy.Fixed)

        layout = QtWidgets.QVBoxLayout()
        layout.addWidget(self.label)
        layout.addWidget(self.canvas)
        layout.setSpacing(0)
        layout.setContentsMargins(0, 0, 0, 0)

        content = QtWidgets.QWidget()
        content.setLayout(layout)
        self.setCentralWidget(content)

        self.load_image('a.jpg')

    def load_image(self, filename):
        image = QtGui.QImage(filename)
        self.canvas.image = image
        self.canvas.setFixedSize(image.width(), image.height())
        self.update()

    def keyPressEvent(self, event):
        self.load_image('b.jpg')


if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())

这看起来像这样，这就是我想要的：

当画布更改为显示较小的图像时，我想相应地缩小窗口以适应。但是，它看起来像这样：

如果我手动拖动来调整它的大小，我可以给窗口的最小大小似乎是适合内容的大小，但为什么它不自动调整大小呢？

标签： pyqt5qt5

Answer 1

当设置了固定大小时，它被用作 sizeHint，后者被布局用来设置小部件的大小。所以画布的大小取决于小部件的大小，但你想要相反。您必须将图像大小缩放到窗口大小：

from PyQt5 import QtCore, QtGui, QtWidgets


class Canvas(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.setSizePolicy(
            QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding
        )
        self.image = QtGui.QImage()

    @property
    def image(self):
        return self._image

    @image.setter
    def image(self, image):
        self._image = image
        self.update()

    def paintEvent(self, event):
        qp = QtGui.QPainter(self)
        if not self.image.isNull():
            image = self.image.scaled(
                self.size(), QtCore.Qt.IgnoreAspectRatio, QtCore.Qt.SmoothTransformation
            )
            qp.drawImage(0, 0, image)


class Window(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()

        self.canvas = Canvas()

        self.label = QtWidgets.QLabel("foobar")
        self.label.setSizePolicy(
            QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Fixed
        )

        layout = QtWidgets.QVBoxLayout()
        layout.addWidget(self.label)
        layout.addWidget(self.canvas)
        layout.setSpacing(0)
        layout.setContentsMargins(0, 0, 0, 0)

        content = QtWidgets.QWidget()
        content.setLayout(layout)
        self.setCentralWidget(content)

        self.load_image("a.jpg")

    def load_image(self, filename):
        image = QtGui.QImage(filename)
        self.canvas.image = image

    def keyPressEvent(self, event):
        self.load_image('b.jpg')
        super().keyPressEvent(event)


if __name__ == "__main__":
    import sys

    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())