如何在 QT 中使用标志作为自定义小部件属性类型？

Question

我无法将标志用作 QT 自定义小部件属性类型。预期的属性未显示在 QT Designer 属性编辑器上。

代码如下：

#ifndef SVBASICDEMO_H
#define SVBASICDEMO_H

#include <QString>
#include <QtUiPlugin/QDesignerExportWidget>
#include <QWidget>
#include <QLabel>
#include "svbasicwidget.h"

QT_BEGIN_NAMESPACE

namespace Company {
namespace Product {
namespace Widget {
namespace Basic {
class QDESIGNER_WIDGET_EXPORT SvBasicDemo : public SvBasicWidget
{
    Q_OBJECT
        Q_FLAGS(SvBasicDemo::AccessTypes)
        Q_PROPERTY(QString url_prop MEMBER url_prop NOTIFY propertyChange)
        Q_PROPERTY(Priority enum_prop MEMBER enum_prop NOTIFY propertyChange)
        Q_PROPERTY(AccessTypes flag_prop MEMBER flag_prop NOTIFY propertyChange)
        Q_PROPERTY(Qt::Alignment flag_prop_2 MEMBER flag_prop_2 NOTIFY propertyChange)

    Q_SIGNALS:
    void propertyChange();

    public slots:
    //更新属性的槽
    void updateProperty();

public:
    SvBasicDemo(QWidget *parent = 0);
    virtual void refresh_binding_cb();
    virtual QString help_info() const;

    enum Priority { High, Low, VeryHigh, VeryLow };
    Q_ENUM(Priority)

    enum AccessType { Read = 0x1, Write = 0x2 };

    Q_DECLARE_FLAGS(AccessTypes, AccessType)

private:
    QString url_prop;
    Priority enum_prop;
    AccessTypes flag_prop;
    Qt::Alignment flag_prop_2;
    QLabel label;
};

Q_DECLARE_OPERATORS_FOR_FLAGS(SvBasicDemo::AccessTypes)

}
}
}
}

QT_END_NAMESPACE
#endif

qt designer 属性编辑器中的结果如下图所示：

您可以看到属性 enum_prop（使用自定义枚举）和 flag_prop_2（使用内置标志 Qt::Alignment）按预期工作。但是属性 flag_prop 不见了。

我研究了"%QT_ROOT%\Qt5.6.0.6\msvc2013\include\QtWidgets\qgraphicsview.h"中的代码。没有搞清楚为什么。

谁能给我一些提示，说明为什么它没有按预期工作？提前致谢。

Answer 1

你有没有添加 Q_DECLARE_FLAGS macro? See also the correct usage of Q_FLAGS()

这是 WindowsStateFlags 定义的示例：

class MyClass
{
public:
    enum Option {
        NoOptions = 0x0,
        ShowTabs = 0x1,
        ShowAll = 0x2,
        SqueezeBlank = 0x4
    };
    Q_DECLARE_FLAGS(Options, Option)
    Q_FLAGS(Options)
    ...
};

Q_DECLARE_OPERATORS_FOR_FLAGS(MyClass::Option)

您必须添加属性宏和可调用函数才能获取当前选项：

Q_PROPERTY(Option option READ getOption())
Q_INVOKABLE Option getOption() const;

并注册元类型 qRegisterMetaType 或 Q_DECLARE_METATYPE():

Q_DECLARE_METATYPE(MyClass::Option);

Answer 2

经过多次尝试，终于解决了这个问题。重点是：

MEMBER 关键字似乎不适用于 Q_FLAGS 属性;

Q_DECLARE_OPERATORS_FOR_FLAGS宏必须在全局命名空间中使用；

namespace Company {

    namespace Product {
    namespace Widget {
    namespace Basic {
    class QDESIGNER_WIDGET_EXPORT SvBasicDemo : public SvBasicWidget
    {
        Q_OBJECT
            Q_FLAGS(AccessTypes)
            Q_PROPERTY(QString url_prop MEMBER url_prop NOTIFY propertyChange)
            Q_PROPERTY(Priority enum_prop MEMBER enum_prop NOTIFY propertyChange)
            // Q_PROPERTY(AccessTypes flag_prop MEMBER flag_prop NOTIFY propertyChange) // Cannot use MEMBER here, otherwise, the property will not show on qt designer property editor. I don't know why.
            Q_PROPERTY(AccessTypes flag_prop READ getAccessTypes WRITE setAccessTypes)
            Q_PROPERTY(Qt::Alignment flag_prop_3 MEMBER flag_prop_2 NOTIFY propertyChange)

    Q_SIGNALS:
    void propertyChange();

    public slots:
    void updateProperty();

public:
    SvBasicDemo(QWidget *parent = 0);
    virtual void refresh_binding_cb();
    virtual QString help_info() const;

    enum Priority { High, Low, VeryHigh, VeryLow };
    Q_ENUM(Priority)

    enum AccessType { None = 0x0, Read = 0x1, Write = 0x2 };
    Q_DECLARE_FLAGS(AccessTypes, AccessType)

    inline AccessTypes getAccessTypes() const
    {
        return flag_prop;
    }
    inline void setAccessTypes(AccessTypes features)
    {
        flag_prop = features;
    }

private:
    QString url_prop;
    Priority enum_prop;
    AccessTypes flag_prop;
    Qt::Alignment flag_prop_2;
    QLabel label;
};
}
}
}
}
// must use this macro outside namespace
Q_DECLARE_OPERATORS_FOR_FLAGS(Company::Product::Widget::Basic::SvBasicDemo::AccessTypes)

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