是否有一个QString
函数接受一个int并将其输出为QString
?
Use QString::number()
:
int i = 42;
QString s = QString::number(i);
And if you want to put it into string within some text context, forget about +
operator. Simply do:
// Qt 5 + C++11
auto i = 13;
auto printable = QStringLiteral("My magic number is %1. That's all!").arg(i);
// Qt 5
int i = 13;
QString printable = QStringLiteral("My magic number is %1. That's all!").arg(i);
// Qt 4
int i = 13;
QString printable = QString::fromLatin1("My magic number is %1. That's all!").arg(i);
Moreover to convert whatever you want, you can use QVariant
. For an int
to a QString
you get:
QVariant(3).toString();
A float
to a string
or a string
to a float
:
QVariant(3.2).toString();
QVariant("5.2").toFloat();
Yet another option is to use QTextStream and the <<
operator in much the same way as you would use cout
in C++:
QPoint point(5,1);
QString str;
QTextStream(&str) << "Mouse click: (" << point.x() << ", " << point.y() << ").";
// OUTPUT:
// Mouse click: (5, 1).
Because operator <<()
has been overloaded, you can use it for multiple types, not just int
. QString::arg()
is overloaded, for example arg(int a1, int a2)
, but there is no arg(int a1, QString a2)
, so using QTextStream()
and operator <<
is convenient when formatting longer strings with mixed types.
Caution: You might be tempted to use the sprintf()
facility to mimic C style printf()
statements, but it is recommended to use QTextStream
or arg()
because they support Unicode string
s.
I always use QString::setNum()
.
int i = 10;
double d = 10.75;
QString str;
str.setNum(i);
str.setNum(d);
setNum()
is overloaded in many ways. See QString
class reference.
In it's simplest form, use the answer of Georg Fritzsche
For a bit advanced, you can use this,
QString QString::arg ( int a, int fieldWidth = 0, int base = 10, const QChar & fillChar = QLatin1Char( ' ' ) ) const
Get the documentation and an example here ..
如果您需要支持区域设置的数字格式,请改用 QLocale::toString。
为了完整起见,您可以使用标准库并执行QString qstr = QString::fromStdString(std::to_string(42));
QLocale has a handy way of converting numbers. It's not much more typing than the accepted answer, but is more useful in the case of floats; so I like to do both this way. Here's for an int:
int i = 42;
QString s = QLocale::toString(i);
and here's for a float:
float f=42.5;
QString s = QLocale::toString(f, 1);
the last argument is the number of decimal places. You can also insert a char format argument such as 'f' or 'e' for the second parameter. The advantage of this, is if your program is then run in a locale where a comma is used as a decimal "point", it will automatically print it that way. It's not included in something like <QCoreApplication>
, so you'll have to do an #include <QLocale>
somewhere, of course. It really comes into its own in formatting currency strings.
You could write:
QString s = QString::number(42.5, 'f', 1);
but according to the help "Unlike QLocale::toString(), this function does not honor the user's locale settings."
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