Qt + Excel 返回QVariant type=9 无...
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发布时间：2023-11-06 01:07
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时间：2024-07-28 07:42
struct Player
{
int number;
QString firstName;
QString lastName;
};
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QVariant
能QVariant使用自定义数据类型做需要使用Q_DECLARE_METATYPE()向Qt元系统声明自定义类型列所示：
struct Player
{
...
};
Q_DECLARE_METATYPE(Player);
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作QVariant传递自定义数据类型需要使用QVariant::fromValue()或者qVariantFromValue：
Player player;
object->setProperty("property", QVariant::fromValue(player));
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更便点自定义类型定义QVariant() 类型转换符：
struct Player
{
...
operator QVariant() const
{
return QVariant::fromValue(*this);
}
};
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我便像面使用：
Player player;
object->setProperty("property", player);
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信号槽
于直接连接类型（默认情况直接连接）言使用自定义数据类型做信号参数需要做其其处理像内置数据类型：
connect(sender, SIGNAL(playerCreated(const Player&)), receiver, SLOT(addPlayer(const Player&)));
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跨线程做编译器给警告：
QObject::connect: Cannot queue arguments of type 'Player'
(Make sure 'Player' is registered using qRegisterMetaType().)
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我需要先注册Player：
qRegisterMetaType("Player");
qRegisterMetaType( ); （面错误除非名字刚类名）
connect(sender, SIGNAL(playerCreated(const Player&)), receiver, SLOT(addPlayer(const Player&)));
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QDebug
能：
qDebug() << player;
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：
qDebug() << "Player(" << player.number << "," << player.firstName << "," << player.lastName << ")";
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做呢我需要QDebug<<操作符重载：
inline QDebug operator<<(QDebug debug, const Player& player)
{
debug.nospace() << "Player("
<< player.number << ","
<< player.firstName << ","
<< player.lastName << ")";
return debug.space();
}
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QDataStream
跟面QDebug像我需要重载<<操作符：
inline QDataStream& operator<<(QDataStream& out, const Player& player)
{
out << player.number;
out << player.firstName;
out << player.lastName;
return out;
}
inline QDataStream& operator>>(QDataStream& in, Player& player)
{
in >> player.number;
in >> player.firstName;
in >> player.lastName;
return in;
}
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QSettings
QSettings 用QVariant保存键值用QDataStream序列化自定义数据（参考面variantToString函数）
能QSettings使用自定义数据类型需要让Qt元系统知道类型像面介绍QVariant部另外要提供相应QDataStream操作符必须注册流操作符：
qRegisterMetaTypeStreamOperators("Player");
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处理我像面使用：
QSettings settings;
Player player;
settings.setValue("key", player);
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QSettings settings;
Player player = value("key").value();
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参考：
QString QSettingsPrivate::variantToString(const QVariant &v)
{
QString result;
switch (v.type()) {
case QVariant::Invalid:
result = QLatin1String("@Invalid()");
break;
case QVariant::ByteArray: {
QByteArray a = v.toByteArray();
result = QLatin1String("@ByteArray(");
result += QString::fromLatin1(a.constData(), a.size());
result += QLatin1Char(')');
break;
}
case QVariant::String:
case QVariant::LongLong:
case QVariant::ULongLong:
case QVariant::Int:
case QVariant::UInt:
case QVariant::Bool:
case QVariant::Double:
case QVariant::KeySequence: {
result = v.toString();
if (result.startsWith(QLatin1Char('@')))
result.prepend(QLatin1Char('@'));
break;
}
#ifndef QT_NO_GEOM_VARIANT
case QVariant::Rect: {
QRect r = qvariant_cast(v);
result += QLatin1String("@Rect(");
result += QString::number(r.x());
result += QLatin1Char(' ');
result += QString::number(r.y());
result += QLatin1Char(' ');
result += QString::number(r.width());
result += QLatin1Char(' ');
result += QString::number(r.height());
result += QLatin1Char(')');
break;
}
case QVariant::Size: {
QSize s = qvariant_cast(v);
result += QLatin1String("@Size(");
result += QString::number(s.width());
result += QLatin1Char(' ');
result += QString::number(s.height());
result += QLatin1Char(')');
break;
}
case QVariant::Point: {
QPoint p = qvariant_cast(v);
result += QLatin1String("@Point(");
result += QString::number(p.x());
result += QLatin1Char(' ');
result += QString::number(p.y());
result += QLatin1Char(')');
break;
}
#endif // !QT_NO_GEOM_VARIANT
default: {
#ifndef QT_NO_DATASTREAM
QByteArray a;
{
QDataStream s(&a, QIODevice::WriteOnly);
s.setVersion(QDataStream::Qt_4_0);
s << v;
}
result = QLatin1String("@Variant(");
result += QString::fromLatin1(a.constData(), a.size());
result += QLatin1Char(')');
#else
Q_ASSERT(!"QSettings: Cannot save custom types without QDataStream support");
#endif
break;
}
}
return result;
}
qsetting让保存ini文件能ascii兼容所
我ini文件键值读入 QVariant 需要两步骤：
文件内些字符转义比 "\x1234\t\0"等所需要 unescape
unescape 字符串构造 QVariant
QVariant写入文件：
QVariant 转换字符串
处理字符串特殊字符即 escape
If you store types that QVariant can't convert to QString (e.g., QPoint, QRect, and QSize), Qt uses an @-based syntax to encode the type. For example:
pos = @Point(100 100)
To minimize compatibility issues, any @ that doesn't appear at the first position in the value or that isn't followed by a Qt type (Point, Rect, Size, etc.) is treated as a normal character.
能转化 QString QVariant @-based 编码base(Point, Rect, Size, etc.)
Although backslash is a special character in INI files, most Windows applications don't escape backslashes (\) in file paths:
windir = C:\Windows
QSettings always treats backslash as a special character and provides no API for reading or writing such entries.
反斜杠能用键值
The INI file format has severe restrictions on the syntax of a key. Qt works around this by using % as an escape character in keys. In addition, if you save a top-level setting (a key with no slashes in it, e.g., "someKey"), it will appear in the INI file's "General" section. To avoid overwriting other keys, if you save something using the a key such as "General/someKey", the key will be located in the "%General" section, not in the "General" section.
key用%转义顶层 keyGeneral段General/someKey"%General"段
Following the philosophy that we should be liberal in what we accept and conservative in what we generate, QSettings will accept Latin-1 encoded INI files, but generate pure ASCII files, where non-ASCII values are encoded using standard INI escape sequences. To make the INI files more readable (but potentially less compatible), call setIniCodec().
意思iniasciinon-ASCII全部转移latin-1例外
