使用QWebEngineView显示html时如何获取verticalScrollBar的最大值和当前值 [英] How can I get the maximum and current value of the verticalScrollBar when displaying html with QWebEngineView

问题描述

我正在尝试在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中获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?

I'm attempting to create a UI in Maya (Python 2.7.11 and Maya Qt 5.6.1. and PySide2) where the OK button is grayed out until the user scrolls to the bottom. I can do this easily with QTextEdit by grabbing the value and maximum from the verticalScrollBar but I can't seem to find similar objects in QWebEngineView or QWebEnginePage. Any Ideas?

推荐答案

如果您想从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内容的对象信息并将其导出到HTML，以便每次滚动状态更改时都会对其进行更新.

In the case you want to get some information from the DOM you have to do it with javascript, in this case we will create an object that will have the required information and export it to the HTML so that each time the scroll status changes it will be updated.

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_())

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