QVariant可以存储的QPolygonF吗？

最新推荐文章于 2024-11-28 15:33:43 发布

原创最新推荐文章于 2024-11-28 15:33:43 发布 · 448 阅读

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本文原创作者：-西门吹雪 MMTS_yang

文章标签：

#QVariant #QPolygon

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本文探讨了如何使用QMetaType在C++中进行类型转换，特别是在处理QPointF等高精度数据时，确保精度并演示了转换过程。重点在于避免精度损失和正确类型判断。

答案：可以
源码如下，构造可以传入Type类型的参数

    enum Type {
        Invalid = QMetaType::UnknownType,
        Bool = QMetaType::Bool,
        Int = QMetaType::Int,
        UInt = QMetaType::UInt,
        LongLong = QMetaType::LongLong,
        ULongLong = QMetaType::ULongLong,
        Double = QMetaType::Double,
        Char = QMetaType::QChar,
        Map = QMetaType::QVariantMap,
        List = QMetaType::QVariantList,
        String = QMetaType::QString,
        StringList = QMetaType::QStringList,
        ByteArray = QMetaType::QByteArray,
        BitArray = QMetaType::QBitArray,
        Date = QMetaType::QDate,
        Time = QMetaType::QTime,
        DateTime = QMetaType::QDateTime,
        Url = QMetaType::QUrl,
        Locale = QMetaType::QLocale,
        Rect = QMetaType::QRect,
        RectF = QMetaType::QRectF,
        Size = QMetaType::QSize,
        SizeF = QMetaType::QSizeF,
        Line = QMetaType::QLine,
        LineF = QMetaType::QLineF,
        Point = QMetaType::QPoint,
        PointF = QMetaType::QPointF,
        RegExp = QMetaType::QRegExp,
        RegularExpression = QMetaType::QRegularExpression,
        Hash = QMetaType::QVariantHash,
        EasingCurve = QMetaType::QEasingCurve,
        Uuid = QMetaType::QUuid,
        ModelIndex = QMetaType::QModelIndex,
        PersistentModelIndex = QMetaType::QPersistentModelIndex,
        LastCoreType = QMetaType::LastCoreType,

        Font = QMetaType::QFont,
        Pixmap = QMetaType::QPixmap,
        Brush = QMetaType::QBrush,
        Color = QMetaType::QColor,
        Palette = QMetaType::QPalette,
        Image = QMetaType::QImage,
        Polygon = QMetaType::QPolygon,
        Region = QMetaType::QRegion,
        Bitmap = QMetaType::QBitmap,
        Cursor = QMetaType::QCursor,
        KeySequence = QMetaType::QKeySequence,
        Pen = QMetaType::QPen,
        TextLength = QMetaType::QTextLength,
        TextFormat = QMetaType::QTextFormat,
        Matrix = QMetaType::QMatrix,
        Transform = QMetaType::QTransform,
        Matrix4x4 = QMetaType::QMatrix4x4,
        Vector2D = QMetaType::QVector2D,
        Vector3D = QMetaType::QVector3D,
        Vector4D = QMetaType::QVector4D,
        Quaternion = QMetaType::QQuaternion,
        PolygonF = QMetaType::QPolygonF,
        Icon = QMetaType::QIcon,
        LastGuiType = QMetaType::LastGuiType,

        SizePolicy = QMetaType::QSizePolicy,

        UserType = QMetaType::User,
        LastType = 0xffffffff // need this so that gcc >= 3.4 allocates 32 bits for Type
    };

    QVariant() Q_DECL_NOTHROW : d() {}
    ~QVariant();
    QVariant(Type type);

那么精度会损失吗？不会

    QVector<QPointF> poss;
    poss.push_back(QPointF(11.999999, 11.009789999));
    poss.push_back(QPointF(22.5677899, 22.00123499));
    poss.push_back(QPointF(33.884455, 33.776655));
    QVariant vecotrPos = QVariant::fromValue(poss);
    //可转换为QVector<QPointF>
    if (vecotrPos.canConvert<QVector<QPointF>>()) {
        QPolygonF pf = vecotrPos.value<QVector<QPointF>>();
        qDebug() << "QVariant to QVector<QPointF>" << pf;
    } else {
        qDebug() << "can not convert QVector<QPointF>";
    }
    //不能转换为QPolygonF
    if (vecotrPos.canConvert<QPolygonF>()) {
        qDebug() << "QVariant to QVector<QPointF>" << vecotrPos.value<QPolygonF>();
    } else {
        qDebug() << "can not convert QPolygonF" << vecotrPos.value<QPolygonF>();
    }

打印如下

QVariant to QVector<QPointF> QPolygonF(QPointF(12,11.0098)QPointF(22.5678,22.0012)QPointF(33.8845,33.7767))
can not convert QPolygonF QPolygonF()