Qt的QVariant类

Posted 2021-01-05 manual-linux

QStandardItemModel类中的函数

bool setData(const QModelIndex &index, const QVariant &value, int role = Qt::EditRole) Q_DECL_OVERRIDE;

中有一个QVariant类型变量。

QVariant类类似于C++联合(union)数据类型，它不仅能够保存很多Qt类型的值，包括QColor,QBrush,QFont,QPen,QString和QSize等，也能够存放Qt的容器类型的值。Qt的很多功能都是建立在QVariant基础上的，如Qt的对象属性及数据库功能等。

DEMO

#include "widget.h"
#include <QDebug>
#include <QVariant>
#include <QColor>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    QVariant v(709);
    qDebug()<<v.toInt();
    QVariant w("how are you!");
    qDebug()<<w.toString();
    //声明一个QMap变量map,使用字符串作为键,QVariant变量作为值
    QMap<QString,QVariant>map;
    map["int"]=709;
    map["double"]=709.709;
    map["string"]="how are you!";  //输入字符串
    map["color"]=QColor(255,0,0);
    //调用相应的转换函数并输出
    qDebug()<<map["int"]<<map["int"].toInt();
    qDebug()<<map["double"]<<map["double"].toDouble();
    qDebug()<<map["string"]<<map["string"].toString();
    qDebug()<<map["color"]<<map["color"].value<QColor>();
    QStringList sl;  //创建一个字符串列表
    sl<<"A"<<"B"<<"C"<<"D";
    QVariant slv(sl);  //将该列表保存在一个QVariant变量中
    //QVariant::type()函数返回存储在QVariant变量中的值的数据类型。
    if(slv.type() == QVariant::StringList)
    {
        QStringList list=slv.toStringList();
        for(int i=0;i<list.size();++i)
        {
            qDebug()<<list.at(i);  //输出列表内容
        }
    }

}

Widget::~Widget()
{

}

运行结果

Qt的常用QVariant::type枚举类型变量

        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