信号 QscrollArea

Question

我想知道是否有可能在每次调整窗口大小时有信号或其他东西知道滚动何时可用以及何时不再可用？import sysfrom PyQt5.QtCore import *from PyQt5.QtWidgets import *class Widget(QWidget):    def __init__(self, parent= None):        super(Widget, self).__init__()        widget = QWidget()        layout = QVBoxLayout(self)        for _ in range(10):            btn = QPushButton()            layout.addWidget(btn)        widget.setLayout(layout)        scroll = QScrollArea()        scroll.setVerticalScrollBarPolicy(Qt.ScrollBarAsNeeded)        scroll.setWidget(widget)        vLayout = QVBoxLayout(self)        vLayout.addWidget(scroll)        self.setLayout(vLayout)if __name__ == '__main__':    app = QApplication(sys.argv)    dialog = Widget()    dialog.show()    app.exec_()

Answer 1

由于 QScrollBar 通常仅在其范围最大值大于 0 时才可见，因此您可以只检查该值。

class Widget(QWidget):

    def __init__(self, parent= None):

        # ....

        # note that the scroll area is now an instance member

        self.scroll = QScrollArea()

        self.scroll.setVerticalScrollBarPolicy(Qt.ScrollBarAsNeeded)

        self.scroll.setWidget(widget)

        self.scroll.verticalScrollBar().rangeChanged.connect(self.checkScrollBarRange)

        vLayout = QVBoxLayout(self)

        vLayout.addWidget(self.scroll)

        self.setLayout(vLayout)

        # the next is important when resizing the widget containing the scroll area

        self.scroll.installEventFilter(self)

    def eventFilter(self, source, event):

        if source == self.scroll and event.type() == QEvent.Resize:

            self.checkScrollBarRange()

        return super().eventFilter(source, event)

    def checkScrollBarRange(self):

        if (self.scroll.verticalScrollBarPolicy() != Qt.ScrollBarAlwaysOff and

            self.scroll.verticalScrollBar().maximum()):

                print('vertical scroll bar IS visible')

        else:

            print('vertical scroll bar NOT visible')