从c++中与Repeater中委托的QML组件进行交互

Question

我无法从c++访问中继器中的委托QML组件。请在下面找到代码。谢谢。

main.cpp

#include <QApplication>
#include <QDebug>
#include <QQuickView>
#include <QQuickItem>
int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QQuickView view;
    view.setSource(QUrl(QStringLiteral("qrc:/Main.qml")));
    view.show();
    QQuickItem *object = view.rootObject();
    QObject *rectangle = object->findChild<QObject*>("rect1");
    if (!rectangle)
    qDebug() << "MyError: rectangle was not found";
    app.exec();
}

Main.qml

import QtQuick 2.4
Row {
    Repeater {
        model: 3
        Rectangle {
            width: 50; height: 50
            color: index %2 ? "black" : "white"
            objectName: "rect" + index
        }
    }
}

控制台输出

:

MyError: rectangle was not found

Answer 1

我在c++中实现了自己的递归函数模板'findChild'函数。'

template <class T>
SearchType findChild(QQuickItem* object, const QString& objectName)
{
        QList<QQuickItem*> children = object->childItems();
        foreach (QQuickItem* item, children)
        {
            if (QQmlProperty::read(item, "objectName").toString() == objectName)
                return item;
            T child = findChild<QQuickItem*>(item, objectName);
            if (child)
                return child;
    }
    return nullptr;
}

并将其称为默认函数。

QQuickItem *object = view.rootObject();
QQuickItem *rectangle = findChild<QQuickItem*>(object, "rect1");
if (rectangle)
{
    qDebug() << rectangle;
    qDebug() << rectangle->objectName();
} 

并得到输出:

QQuickRectangle(0x2222b40, name="rect1", parent=0x22245b0, geometry=50,0 50x50)
"rect1"

Answer 2

如果您调用object->dumpObjectTree()，您将看到类似以下控制台输出的内容:

QQuickRow:: 
QQuickRepeater:: 
    QQmlComponent::

如您所见，对象树不包含作为专用对象的矩形。在我对QML方面的有限理解中，有另一个树包含所有可见的QML项目/组件。您至少可以通过qml中的'children'属性访问它们。为了显示这一点，我将qml文件更改为:

Main.qml:

Row {
    id: row
    Repeater {
        model: 3
        Rectangle {
            width: 50; height: 50
            color: index %2 ? "black" : "white"
            objectName: "rect" + index
        }
    }
    Component.onCompleted: {
        console.log(row.children[0].objectName);
        console.log(row.children[1].objectName);
        console.log(row.children[2].objectName);
    }
}

输出如下:

qml: rect0
qml: rect1
qml: rect2
MyError: rectangle was not found

当然，直接可访问性和索引取决于您的附加项目/组件。从这里开始，您可以编写自己的递归'findChild'函数并将结果对象公开给c++。下面是如何描述的:http://doc.qt.io/qt-5/qtqml-cppintegration-interactqmlfromcpp.html

例如，您可以在qml中像这样实现'findChild':

function findChild(propertyName, propertyValue) {
    return findChildRecursivly(row, propertyName, propertyValue)
}

这个qml函数可以像

一样从c++中调用

QVariant result;
QMetaObject::invokeMethod(object, "findChild",
                          Q_RETURN_ARG(QVariant, result),
                          Q_ARG(QVariant, "objectName"),
                          Q_ARG(QVariant, "rect1"));
rectangle = result.value<QObject *>();

加上以下代码行:

if (!rectangle)
{
    qDebug() << "MyError: rectangle was not found";
}
else
{
    qDebug() << rectangle;
    qDebug() << rectangle->objectName();
}

得到以下输出:

QQuickRectangle(0x1c1beef, name = "rect1")
"rect1"