使用QWebEngineView显示html时如何获取verticalScrollBar的最大值和当前值

Question

我试图在Maya（Python 2.7.11和Maya Qt 5.6.1。和PySide2）中创建UI，在该UI中，“确定”按钮显示为灰色，直到用户滚动到底部。 我可以通过从verticalScrollBar抓取值和最大值来轻松实现QTextEdit的功能，但在QWebEngineView或QWebEnginePage中似乎找不到类似的对象。 有任何想法吗？

Answer 1

如果要从DOM中获取一些信息，则必须使用javascript进行处理，在这种情况下，我们将创建一个具有所需信息的对象，并将其导出到HTML，以便每次滚动状态更改时，被更新。

from PySide2 import QtCore, QtWidgets, QtWebEngineWidgets, QtWebChannel
from jinja2 import Template

class Element(QtCore.QObject):
    def __init__(self, name, parent=None):
        super(Element, self).__init__(parent)
        self._name = name

    @property
    def name(self):
        return self._name

    def script(self):
        return ''

class YScrollBarListener(Element):
    valueChanged = QtCore.Signal(int)
    maximumChanged = QtCore.Signal(int)

    def __init__(self, name, parent=None):
        super(YScrollBarListener, self).__init__(name, parent)
        self._value = -1
        self._maximum = -1

    @QtCore.Property(int, notify=valueChanged)
    def value(self):
        return self._value

    @QtCore.Property(int, notify=maximumChanged)
    def maximum(self):
        return self._maximum

    def script(self):
        _script = '''
        window.addEventListener("scroll", function(event){
            {{name}}.update_value(this.scrollY);
            // https://stackoverflow.com/a/43571388/6622587
            var scrollMaxY = window.scrollMaxY || (document.documentElement.scrollHeight - document.documentElement.clientHeight)
            {{name}}.update_maximum(scrollMaxY)
        });
        '''
        return Template(_script).render(name=self.name)

    @QtCore.Slot(int)
    def update_value(self, value):
        if self._value != value:
            self._value = value
            self.valueChanged.emit(value)

    @QtCore.Slot(int)
    def update_maximum(self, maximum):
        if self._maximum != maximum:
            self._maximum = maximum
            self.maximumChanged.emit(maximum)

class WebEnginePage(QtWebEngineWidgets.QWebEnginePage):
    def __init__(self, *args, **kwargs):
        super(WebEnginePage, self).__init__(*args, **kwargs)
        self.loadFinished.connect(self.onLoadFinished)
        self._objects = []

    def add_object(self, obj):
        self._objects.append(obj)

    @QtCore.Slot(bool)
    def onLoadFinished(self, ok):
        print("Finished loading: ", ok)
        if ok:
            self.load_qwebchannel()
            self.add_objects()

    def load_qwebchannel(self):
        file = QtCore.QFile(":/qtwebchannel/qwebchannel.js")
        if file.open(QtCore.QIODevice.ReadOnly):
            content = file.readAll()
            file.close()
            self.runJavaScript(content.data().decode())
        if self.webChannel() is None:
            channel = QtWebChannel.QWebChannel(self)
            self.setWebChannel(channel)

    def add_objects(self):
        if self.webChannel() is not None:
            objects = {obj.name : obj for obj in self._objects}
            self.webChannel().registerObjects(objects)
            _script = '''
            {% for obj in objects %}
            var {{obj}};
            {% endfor %}
            new QWebChannel(qt.webChannelTransport, function (channel) {
            {% for obj in objects %}
                {{obj}} = channel.objects.{{obj}};
            {% endfor %}
            }); 
            '''
            self.runJavaScript(Template(_script).render(objects=objects.keys()))
            for obj in self._objects:
                if isinstance(obj, Element):
                    self.runJavaScript(obj.script())

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

        self._scrollbar_listener = YScrollBarListener("y_scrollbar_listener", self)
        self._scrollbar_listener.valueChanged.connect(self.on_y_value_changed)
        view = QtWebEngineWidgets.QWebEngineView()
        page = WebEnginePage(view)
        page.add_object(self._scrollbar_listener)
        view.setPage(page)

        view.load(QtCore.QUrl("https://stackoverflow.com/questions/43282899"))

        self._button = QtWidgets.QPushButton("button")
        progressbar = QtWidgets.QProgressBar(maximum=100)
        view.loadProgress.connect(progressbar.setValue)

        lay = QtWidgets.QVBoxLayout(self)
        lay.addWidget(view)
        lay.addWidget(self._button)
        lay.addWidget(progressbar)

        self.resize(640, 480)

    def on_y_value_changed(self, value):
        self._button.setEnabled(self._scrollbar_listener.maximum != value)


if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    app.setStyle('fusion')
    app.setStyleSheet('''
    QPushButton
    {
        background-color: #2E8B57;
    }
    QPushButton:disabled
    {
        background-color: #FFFAFA;
    }
    ''')
    w = Widget()
    w.show()
    sys.exit(app.exec_())