在 PyQt5 中获取滚动条缩略图的 size/width？

Question

比如说，你有一个 PyQt5 滚动条：

我想以编程方式找到滚动条的宽度 "thumb"（编辑：在 http://pyqt.sourceforge.net/Docs/PyQt4/qscrollbar.html 中称为 "slider"），以及它的位置；我猜一开始像素是 "natural" 单位。

从上图中，我猜想 start 始终为 0 - 但我能否获取 left、right、width（虽然，如果我们有 left 和 right，width 是平凡的 right-left）； end 以像素为单位？

我知道存在 QScrollBar 的 .value()、pageStep() 和 singleStep()，但我无法确定它们是否与上述尺寸（以像素为单位）相关.

（如果滚动条需要 PyQt5 示例，请参见我在 Have tabs keep focus on mousewheel over them in a PyQt5 scrollarea? 中发布的代码）

Answer 1

在这种情况下，您必须使用QStyle() 的subControlRect() 方法来获取您可以从中获取所需信息的矩形。

在下面的示例中，我创建了 QScrollBar 的自定义 class，每当滑块的位置发生变化或 QScrollBar 的大小时，它都会通过信号发出该信息。

from PyQt5 import QtCore, QtGui, QtWidgets

class Scrollbar(QtWidgets.QScrollBar):
    geometryChanged = QtCore.pyqtSignal(int, int, int, int, int)

    def __init__(self, parent=None):
        super(Scrollbar, self).__init__(parent)
        self.sliderMoved.connect(self.calculate_geometry)

    def resizeEvent(self, event):
        self.calculate_geometry()
        super(Scrollbar, self).resizeEvent(event)

    def calculate_geometry(self):
        opt = QtWidgets.QStyleOptionSlider()
        self.initStyleOption(opt)
        gr = self.style().subControlRect(QtWidgets.QStyle.CC_ScrollBar, opt,
            QtWidgets.QStyle.SC_ScrollBarGroove, self)
        sr = self.style().subControlRect(QtWidgets.QStyle.CC_ScrollBar, opt,
            QtWidgets.QStyle.SC_ScrollBarSlider, self)

        start = gr.left() if self.orientation() == QtCore.Qt.Horizontal else gr.top()
        left = sr.left() if self.orientation() == QtCore.Qt.Horizontal else sr.top()
        right = sr.right() if self.orientation() == QtCore.Qt.Horizontal else sr.bottom()
        width = sr.width() if self.orientation() == QtCore.Qt.Horizontal else sr.height()
        end = gr.right() if self.orientation() == QtCore.Qt.Horizontal else gr.bottom()
        self.geometryChanged.emit(start, left, width, right, end)

class Widget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(Widget, self).__init__(parent)

        hlayv = QtWidgets.QHBoxLayout()
        hlayv.addWidget(QtWidgets.QLabel("start: "))
        self._start_label_v = QtWidgets.QLabel()
        hlayv.addWidget(self._start_label_v)
        hlayv.addWidget(QtWidgets.QLabel("left: "))
        self._left_label_v = QtWidgets.QLabel()
        hlayv.addWidget(self._left_label_v)
        hlayv.addWidget(QtWidgets.QLabel("width: "))
        self._width_label_v = QtWidgets.QLabel()
        hlayv.addWidget(self._width_label_v)
        hlayv.addWidget(QtWidgets.QLabel("right: "))
        self._right_label_v = QtWidgets.QLabel()
        hlayv.addWidget(self._right_label_v)
        hlayv.addWidget(QtWidgets.QLabel("end: "))
        self._end_label_v = QtWidgets.QLabel()
        hlayv.addWidget(self._end_label_v)

        hlayh = QtWidgets.QHBoxLayout()
        hlayh.addWidget(QtWidgets.QLabel("start: "))
        self._start_label_h = QtWidgets.QLabel()
        hlayh.addWidget(self._start_label_h)
        hlayh.addWidget(QtWidgets.QLabel("left: "))
        self._left_label_h = QtWidgets.QLabel()
        hlayh.addWidget(self._left_label_h)
        hlayh.addWidget(QtWidgets.QLabel("width: "))
        self._width_label_h = QtWidgets.QLabel()
        hlayh.addWidget(self._width_label_h)
        hlayh.addWidget(QtWidgets.QLabel("right: "))
        self._right_label_h = QtWidgets.QLabel()
        hlayh.addWidget(self._right_label_h)
        hlayh.addWidget(QtWidgets.QLabel("end: "))
        self._end_label_h = QtWidgets.QLabel()
        hlayh.addWidget(self._end_label_h)

        self.scrollarea = QtWidgets.QScrollArea()
        content_widget = QtWidgets.QLabel()
        content_widget.setStyleSheet('''background-color : red;''')
        content_widget.setFixedSize(1000, 1000)
        self.scrollarea.setWidget(content_widget)
        hscrollbar = Scrollbar()
        hscrollbar.geometryChanged.connect(self.on_vertical_geometryChanged)
        self.scrollarea.setHorizontalScrollBar(hscrollbar)
        self.scrollarea.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)

        vscrollbar =Scrollbar()
        self.scrollarea.setVerticalScrollBar(vscrollbar)
        vscrollbar.geometryChanged.connect(self.on_horizontal_geometryChanged)
        self.scrollarea.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)

        vlay = QtWidgets.QVBoxLayout(self)
        vlay.addWidget(QtWidgets.QLabel("<b>Vertical: </b>"))
        vlay.addLayout(hlayv)
        vlay.addWidget(QtWidgets.QLabel("<b>Horizontal: </b>"))
        vlay.addLayout(hlayh)
        vlay.addWidget(self.scrollarea)

    @QtCore.pyqtSlot(int, int, int, int, int)
    def on_vertical_geometryChanged(self, start, left, width, right, end):
        self._start_label_v.setNum(start)
        self._left_label_v.setNum(left)
        self._width_label_v.setNum(width)
        self._right_label_v.setNum(right)
        self._end_label_v.setNum(end)

    QtCore.pyqtSlot(int, int, int, int, int)
    def on_horizontal_geometryChanged(self, start, left, width, right, end):
        self._start_label_h.setNum(start)
        self._left_label_h.setNum(left)
        self._width_label_h.setNum(width)
        self._right_label_h.setNum(right)
        self._end_label_h.setNum(end)

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

在 PyQt5 中获取滚动条缩略图的 size/width？

Getting the size/width of a scrollbar thumb in PyQt5?

python

pyqt

pyqt5

qscrollbar