c++ - 如何与 Sailfish Silica/QML 中的 Slider 的值进行交互？

Question

我似乎完全迷失在 QML 中的表单声明中。我有一个正确设置了 Q_PROPERTies 的 C++ 对象，我可以访问 QML 中该类的对象，并且我想在 QML 中使用 slider 。如何使 Slider 的值更新对象中属性的信息，反之亦然？

Answer 1

如果它与常规 QML 类似，则以下方法可行。

上下文属性

使用明确的 Binding或使用 Slider的 valueChanged 信号:

#include <QGuiApplication>
#include <QtQml>

class Object : public QObject
{
    Q_OBJECT
    Q_PROPERTY(qreal value READ value WRITE setValue NOTIFY valueChanged)
public:
    explicit Object(QObject *parent = 0) :
        QObject(parent),
        mValue(0)
    {
    }

    qreal value() const {
        return mValue;
    }

    void setValue(qreal value) {
        if (value != mValue) {
            mValue = value;
            emit valueChanged();
        }
    }
signals:
    qreal valueChanged();
private:
    qreal mValue;
};

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    Object object;

    QQmlApplicationEngine engine;
    engine.rootContext()->setContextProperty("object", &object);
    engine.load(QUrl(QStringLiteral("qrc:///main.qml")));

    return app.exec();
}

#include "main.moc"

ma​​in.qml:

import QtQuick 2.3
import QtQuick.Controls 1.2

ApplicationWindow {
    width: 400
    height: 400
    visible: true

    Binding {
        target: object
        property: "value"
        value: slider.value
    }

    Slider {
        id: slider
        // You can also react to the valueChanged signal of Slider:
        //onValueChanged: object.value = value
    }
}

注册的QML类型

使用简单的绑定(bind):

#include <QGuiApplication>
#include <QtQml>

class Object : public QObject
{
    Q_OBJECT
    Q_PROPERTY(qreal value READ value WRITE setValue NOTIFY valueChanged)
public:
    explicit Object(QObject *parent = 0) :
        QObject(parent),
        mValue(0)
    {
    }

    qreal value() const {
        return mValue;
    }

    void setValue(qreal value) {
        if (value != mValue) {
            mValue = value;
            emit valueChanged();
        }
    }
signals:
    qreal valueChanged();
private:
    qreal mValue;
};

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    qmlRegisterType<Object>("Test", 1, 0, "Object");

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:///main.qml")));

    return app.exec();
}

#include "main.moc"

ma​​in.qml:

import QtQuick 2.3
import QtQuick.Controls 1.2

import Test 1.0

ApplicationWindow {
    width: 400
    height: 400
    visible: true

    Object {
        id: object
        value: slider.value
        onValueChanged: print(value)
    }

    Slider {
        id: slider
    }
}