PyQt5：當屬性值改變時通知

Question

首先，請看下面給出的代碼示例。 例如，當QGraphicsView的屬性self.markup_points的值發生更改時，如何訪問QPushButton上的.setDisabled(...) ？ 我如何使用 pyqt 信號或...使用單例來實現這一點？

class ImageView(QtWidgets.QGraphicsView):
    def __init__(self, parent):
        super(ImageView, self).__init__(parent)
        self.markup_points = []
        ...
        ...

    def set_image(self, pixmap):
        foo()

    def mousePressEvent(self, event):
        foo()
        self.markup_points.append(QtCore.QPointF(bar()))
        super(ImageView, self).mousePressEvent(event)
    ...

    def keyPressEvent(self, event):
        key = event.key()
        modifiers = int(event.modifiers())
        if (modifiers and modifiers & MOD_MASK == modifiers and
                key > 0 and key != QtCore.Qt.Key_Control and key != QtCore.Qt.Key_Meta):
            if key == 88:
                self.remove_point()

    def remove_point(self):
        if len(self.markup_points):
            self.markup_points.pop()
    ...

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self):
        super(MainWindow, self).__init__()
        self.setupUi(self)
        ...
        self.imageView = ImageView()
        self.btnLoad.clicked.connect(self._load_combination)
        self.btnSkip.clicked.connect(self._skip_combination)
        self.btnSave.clicked.connect(self._save_objects)
        # qpushbutton that I want to access later
        self.btnRemove.clicked.connect(self.imageView.remove_point)
    ...
    def event_if_something_is_changed_in_image_view(self):
        self.btnRemove.setDisabled(True)

Answer 1

為什么你認為單例是解決方案？ 單例是一種反模式，因此應該避免使用，並且僅在某些情況下是必要的，此外它與通知更改無關，因此丟棄它。

解決方案是創建一個在發生變化時發出的信號，並將其連接到接收通知的插槽：

class ImageView(QtWidgets.QGraphicsView):
    markupPointsChanged = QtCore.pyqtSignal(list) # <---

    def __init__(self, parent):
        super(ImageView, self).__init__(parent)
        self.markup_points = []
        # ...

    def mousePressEvent(self, event):
        foo()
        self.append_point(QtCore.QPointF(bar()))
        super(ImageView, self).mousePressEvent(event)

    def keyPressEvent(self, event):
        key = event.key()
        modifiers = int(event.modifiers())
        if (modifiers and modifiers & MOD_MASK == modifiers and
                key > 0 and key not in (QtCore.Qt.Key_Control, QtCore.Qt.Key_Meta)):
            if key == QtCore.Qt.Key_X:
                self.remove_point()

    def append_point(self, p):
        self.markup_points.append(p)
        self.markupPointsChanged.emit(self.markup_points)  # <---

    def remove_point(self):
        if self.markup_points:
            self.markup_points.pop()
        self.markupPointsChanged.emit(self.markup_points) # <---
    # ...

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self):
        super(MainWindow, self).__init__()
        self.setupUi(self)
        # ...
        self.imageView = ImageView()
        self.btnLoad.clicked.connect(self._load_combination)
        self.btnSkip.clicked.connect(self._skip_combination)
        self.btnSave.clicked.connect(self._save_objects)
        self.btnRemove.clicked.connect(self.imageView.remove_point)
        self.imageView.markupPointsChanged.connect(self.on_markupPointsChanged) # <---

    @QtCore.pyqtSlot(list)
    def on_markupPointsChanged(self, points):
        print(points)
        self.btnRemove.setDisabled(True)