如何获取指定objectName的QObject

作者 qyvlik

如下QML代码，设置了一个 objectName 为 YOUR_OBJECT_NAME 的 QML 对象，现在需要在 c++ 代码中获取到他。

//~ main.qml
import QtQuick 2.0
import QtQuick.Controls 2.0

ApplicationWindow {
    visible: true

    QtObject {
        objectName: "YOUR_OBJECT_NAME"
    }
}

如下 c++ 代码，试图通过 findChild 函数来获取 objectName 为 YOUR_OBJECT_NAME 的 QML 对象，但是却返回空。

QQmlApplicationEngine engine;
engine.load("main.qml");

QList<QObject*> rootObjects = engine.rootObjects();

QObject* root = Q_NULLPTR;
foreach (QObject* iter, rootObjects) {
    if (iter->objectName() == "root") {
        root = iter;
        break;
    }
}

QObject* YOUR_OBJECT_NAME = root->findChild<QObject*>("YOUR_OBJECT_NAME", Qt::FindDirectChildrenOnly);
qDebug() << "YOUR_OBJECT_NAME:" << YOUR_OBJECT_NAME;

在仔细阅读代码，以及测试，发现，上诉代码 root->findChild 只能获取到父类为 Item 的对象；父类为 QtObject 的对象，其父亲为 Window::contentItem 或者 ApplicationWindow::contentItem。这里给出通过 objectName 获取 QML 对象的代码：

QObject *findClindByObjectNameFromQmlEngine(QQmlApplicationEngine *qmlEngine, QString objectName)
{
    if (qmlEngine == Q_NULLPTR) {
        return Q_NULLPTR;
    }

    QList<QObject*> rootObjects = qmlEngine->rootObjects();
    QObject* child = Q_NULLPTR;

    foreach (QObject* iter, rootObjects) {
        if (iter->inherits("QQuickItem")) {
            child = iter->findChild<QObject*>(objectName);
            break;
        }

        child = iter->findChild<QObject*>(objectName);
        if (child != Q_NULLPTR) {
            break;
        }

        QObject* contentItem = iter->property("contentItem").value<QObject*>();
        if (contentItem != Q_NULLPTR) {
            child = contentItem->findChild<QObject*>(objectName);
            break;
        }
    }
    return child;
}