用已知的QMetaType::Type到QVariant反序列化QVariant

Question

我有一个包含变量原始数据的QByteArray。

描述变量的QMetaType::Type是已知的。

我想将这个变量反序列化为一个QVariant

有以下投入：

QByteArray bytes; // Consider it initialized
QMetaType::Type type; // Same

到目前为止，我的尝试并没有奏效：

QVariant var{bytes};
var.convert(type); // Does not work, apparently QVariant expects bytes to be a string representation of the variable

QDataStream ds(bytes, QIODevice::ReadOnly);
QVariant var;
ds >> var; // Does not work because bytes does not come from the serialization of a QVariant (especially, it lacks type information)

我不能更改输入或输出类型：

输入必须是QMetaType::Type.

• The类型，而QMetaType::Type.

• The输出必须是QVariant

类型

例子：

//Inputs
QByteArray bytes = { 0x12, 0x34, 0x56, 0x78 };
QMetaType::Type type = QMetaType::UInt; // Suppose the size of unsigned int is 4 bytes (could be 2)
// Note: this is an example, in pratice I have to manage many types, including double

//Expected output:
QVariant var = deserialize(bytes, type);
// var.type() == QMetaType::UInt
// var.toUInt() == 305419896 (== 0x12345678)

Answer 1

面对同样的问题，我使用提供的类型id直接通过QByteArray的data()方法从QByteArray构建data()：

QByteArray bytes; // Consider it initialized
QMetaType::Type type; // Same
QVariant result(type.id(),bytes.data());

如果构造失败，您将得到一个无效的QVariant，但到目前为止，对于我的类型，它工作得很好。

Answer 2

您可以将其写入unsigned int，然后将其转换为QVariant

    const char data[] = { 0x12, 0x34, 0x56, 0x78 };
    QByteArray bytes { QByteArray::fromRawData( data, 4) };

    QDataStream s {&bytes, QIODevice::ReadOnly};
    //write out the data to uint
    unsigned int x{};
    s >> x;

    //create a Qvariant from it
    QVariant var{x};

    qDebug () << "x: " << x;                       //305419896
    qDebug () << "variant: " << var;               //QVariant(uint, 305419896)
    qDebug () << "variant uint: " << var.toUInt(); //305419896

或者，您也可以直接构造一个QVariant。

    auto v = QVariant(bytes.toHex().toUInt());
    //auto v = QVariant(bytes.toUInt());            //this will not work
    qDebug () << "Bytes to uint; " << v.toUInt(); //305419896