如何从我的 Python 文件中更新 Qml 对象的属性?

A disadvantage of this method is that if the relation of the object with the rootobject is complex(Sometimes objects that are in other QMLs are hard to access with findChild) the part of accessing the object becomes complicated and sometimes impossible so this method will fail. Another problem is that when using the objectName as the main search data there is a high dependency of the Python layer to the QML layer since if the objectName is modified in QML the logic in python would have to be modified. Another disadvantage is that by not managing the life cycle of the QML object it could be eliminated without Python knowing so it would access an incorrect reference causing the application to terminate unexpectedly.

• 创建一个具有相同类型属性的 QObject.
• 使用 setContextProperty 导出到 QML.
• 在 QObject 的属性和 item 的属性之间进行绑定.

ma​​in.qml

import QtQuick 2.11
import QtQuick.Window 2.2
import QtQuick.Controls 2.2

ApplicationWindow {    
    visible: true
    width: Screen.width/2
    height: Screen.height/2
    Rectangle {
        id: rectangle
        x: 187
        y: 92
        width: r_manager.width
        height: r_manager.height
        color: "blue"
    }
}

ma​​in.py

import os
import sys
from PyQt5 import QtCore, QtGui, QtQml
from functools import partial

class RectangleManager(QtCore.QObject):
    widthChanged = QtCore.pyqtSignal(float)
    heightChanged = QtCore.pyqtSignal(float)

    def __init__(self, parent=None):
        super(RectangleManager, self).__init__(parent)
        self._width = 100
        self._height = 100

    @QtCore.pyqtProperty(float, notify=widthChanged)
    def width(self):
        return self._width

    @width.setter
    def width(self, w):
        if self._width != w:
            self._width = w
            self.widthChanged.emit(w)

    @QtCore.pyqtProperty(float, notify=heightChanged)
    def height(self):
        return self._height

    @height.setter
    def height(self, h):
        if self._height != h:
            self._height = h
            self.heightChanged.emit(h)

def testing(r):
    import random
    print("width: {}, height: {}".format(r.width, r.height))
    r.width = random.randint(100, 400)
    r.height = random.randint(100, 400)

def run():
    myApp = QtGui.QGuiApplication(sys.argv)
    myEngine = QtQml.QQmlApplicationEngine()
    manager = RectangleManager()
    myEngine.rootContext().setContextProperty("r_manager", manager)
    directory = os.path.dirname(os.path.abspath(__file__))
    myEngine.load(QtCore.QUrl.fromLocalFile(os.path.join(directory, 'main.qml')))

    if not myEngine.rootObjects():
        return -1
    timer = QtCore.QTimer(interval=500)
    timer.timeout.connect(partial(testing, manager))
    timer.start()
    return myApp.exec_()

if __name__ == "__main__":
    sys.exit(run())

缺点是您必须编写更多代码.优点是对象可以被所有 QML 访问，因为它使用 setContextProperty，另一个优点是如果 QML 对象被删除，它不会产生问题，因为只消除了绑定.最后，通过不使用 objectName，依赖项不存在.