QQmlApplicationEngine 列表索引超出范围问题

Question

我正在尝试运行来自这个 website 的最后 2 个示例并以 root = engine.rootObjects()[0] # type: QObject IndexError: list index out of range 两个示例的错误（根布局的信号连接）（其他 qml 文件的信号连接）

如果有帮助，我将所有示例文件放在同一目录级别并将导入语句更改为 Pyside6（来自 PySide6.QtCore...）而不是 PySide2。如果它更容易看到，我还添加了我的代码版本：

main.py:

import sys

from PySide6.QtCore import *
from PySide6.QtQml import QQmlApplicationEngine
from PySide6.QtWidgets import QApplication


def say(s):
    print(s)


if __name__ == '__main__':
    app = QApplication()
    engine = QQmlApplicationEngine()
    engine.load(QUrl.fromLocalFile('main.qml'))
    # Get the root object.
    root = engine.rootObjects()[0]  # type: QObject
    # Find the target object. Since our target object is Window, which is the root object. So use it directly.
    target_view = root
    # Bind signal.
    target_view.say.connect(say)  # The former one is the signal of qml, and the latter one is from Python
    # say() method.
    
    sys.exit(app.exec())

main.qml:

import QtQuick 2.14
import QtQuick.Controls 2.14
import QtQuick.Window 2.12

Window {
    visible: true
    width: 600; height: 400

    signal say(string s)

    Button {
        text: "hello"
        onClicked: say(text)
    }
}

Answer 1

错误的可能原因是：

.qml 的路径不正确，因此未加载.qml。
.qml 的加载并不像您假设的那样同步。
.qml 有一些错误（例如语法）

综合以上，解决方案是：

import os
import sys
from pathlib import Path

from PySide6.QtCore import QCoreApplication, Qt, QUrl
from PySide6.QtQml import QQmlApplicationEngine
from PySide6.QtWidgets import QApplication

CURRENT_DIRECTORY = Path(__file__).resolve().parent


def say(s):
    print(s)


if __name__ == "__main__":
    app = QApplication()
    engine = QQmlApplicationEngine()
    filename = os.fspath(CURRENT_DIRECTORY / "main.qml")
    url = QUrl.fromLocalFile(filename)

    def handle_object_created(obj, obj_url):
        if obj is None and url == obj_url:
            QCoreApplication.exit(-1)
        else:
            root = engine.rootObjects()[0]
            target_view = root
            target_view.say.connect(say)

    engine.objectCreated.connect(handle_object_created, Qt.QueuedConnection)
    engine.load(url)

    sys.exit(app.exec())

但无论如何我不喜欢使用 rootObjects 而是导出 QObject:

import os
import sys
from pathlib import Path

from PySide6.QtCore import QCoreApplication, QObject, Qt, QUrl, Signal
from PySide6.QtQml import QQmlApplicationEngine
from PySide6.QtWidgets import QApplication

CURRENT_DIRECTORY = Path(__file__).resolve().parent


class Helper(QObject):
    say = Signal(str)


def say(s):
    print(s)


if __name__ == "__main__":
    app = QApplication()
    engine = QQmlApplicationEngine()

    helper = Helper()
    helper.say.connect(say)

    engine.rootContext().setContextProperty("helper", helper)

    filename = os.fspath(CURRENT_DIRECTORY / "main.qml")
    url = QUrl.fromLocalFile(filename)

    def handle_object_created(obj, obj_url):
        if obj is None and url == obj_url:
            QCoreApplication.exit(-1)

    engine.objectCreated.connect(handle_object_created, Qt.QueuedConnection)
    engine.load(url)

    sys.exit(app.exec())

import QtQuick 2.14
import QtQuick.Controls 2.14
import QtQuick.Window 2.12

Window {
    visible: true
    width: 600
    height: 400

    Button {
        text: "hello"
        onClicked: helper.say(text)
    }

}

QQmlApplicationEngine 列表索引超出范围问题

QQmlApplicationEngine list index out of range issue

qt

qml

pyside