定义自定义属性组

Question

如何在qml中定义自定义属性组，等于锚属性?

使用例子:

Item {
  anchors {
    leftMargin: 5
    rightMargin: 5
  }
}

Answer 1

恐怕这并不像你想象的那么简单。

据我所知，你有两个选择:

1。-遵循@BaCaRoZzo提供的链接中的建议，并实现自己的对象类型。

2。用c++编写一个更复杂的QML类型，并在你的QML文件中使用它。或多或少是@folibis指出的观点。例子:

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QtQml>
#include "customitem.h"
int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);
    qmlRegisterType<CustomItem>("CustomItem", 1,0, "CustomItem");
    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    return app.exec();
}

customitem.h

#ifndef CUSTOMITEM_H
#define CUSTOMITEM_H
#include <QObject>
class CustomItem: public QObject
{
    Q_OBJECT
    /*
     * Any property that is writable should have an associated NOTIFY signal.
     * Ref: http://doc.qt.io/qt-5/qtqml-cppintegration-exposecppattributes.html#exposing-properties
     */
    Q_PROPERTY(int x READ x WRITE setX NOTIFY xChanged)
    Q_PROPERTY(int y READ y WRITE setY NOTIFY yChanged)

public:
    CustomItem(QObject *parent = 0);
    int x() const;
       void setX(int);
       int y() const;
       void setY(int);
private:
    int m_x;
    int m_y;
signals:
    void xChanged();
    void yChanged();
public slots:
};
#endif // CUSTOMITEM_H

customitem.cpp

#include "customitem.h"
CustomItem::CustomItem(QObject *parent)
: QObject(parent), m_x(0), m_y(0)
{
}
int CustomItem::x() const
{
    return m_x;
}
void CustomItem::setX(int x)
{
    m_x = x;
}
int CustomItem::y() const
{
    return m_y;
}
void CustomItem::setY(int y)
{
    m_y = y;
}

main.qml

import QtQuick 2.5
import QtQuick.Window 2.2
import CustomItem 1.0
Window {
    visible: true
    CustomItem {
        id: customItem
        x: 50
        y: 50
    }
    Rectangle {
        id: rect
        x: customItem.x
        y: customItem.y
        width: 100; height: 100
        color: "red"
    }    
}