python - 如何使用 PySide2 在 qml 中设置值？

Question

从 PySide2 我想将值写入 qml。该值动态变化。

这里的 PyQt5 示例:How to set values in qml using PyQt5?

main.py:

import sys

from PySide2.QtCore import QObject, Signal, Property, QUrl, QTimer, QDateTime
from PySide2.QtGui import QGuiApplication
from PySide2.QtQml import QQmlApplicationEngine

class Foo(QObject):
    textChanged = Signal()

    def __init__(self, parent=None):
        QObject.__init__(self, parent)
        self._text = ""

    @Property(str, notify=textChanged)
    def text(self):
        return self._text

    @text.setter
    def text(self, value):
        if self._text == value:
            return
        self._text = value
        self.textChanged.emit()


def update_value():
    obj.text = "values from PyQt5 :-D : {}".format(QDateTime.currentDateTime().toString())

if __name__ == "__main__":
    app = QGuiApplication(sys.argv)
    obj = Foo()
    timer = QTimer()
    timer.timeout.connect(update_value)
    timer.start(100)
    engine = QQmlApplicationEngine()
    engine.rootContext().setContextProperty("obj", obj)
    engine.load(QUrl("main.qml"))
    if not engine.rootObjects():
        sys.exit(-1)
    sys.exit(app.exec_())

main.qml:

import QtQuick 2.5
import QtQuick.Window 2.2

Window {
    id: parwin
    visible: true
    width: 640
    height: 480
    Text{
        anchors.fill: parent
        text:  obj.text
    }

}

我遇到错误:

main.qml:11:9: Unable to assign [undefined] to QString
main.qml:11: TypeError: Cannot read property 'text' of null

请告诉我我的错误在哪里？

Answer 1

PySide2 的 setter 似乎有一个 bug，因此它无法正确注册 Property，解决方案是创建一个具有不同名称的 setter 和 getter，并分别使用 Property() 来公开它:

# ...

class Foo(QObject):
    textChanged = Signal()

    def __init__(self, parent=None):
        QObject.__init__(self, parent)
        self._text = ""

    <b>def get_text(self):</b>
        return self._text

    <b>def set_text(self, value):</b>
        if self._text == value:
            return
        self._text = value
        self.textChanged.emit()

    <b>text = Property(str, fget=get_text, fset=set_text, notify=textChanged)</b>

# ...