将格式化的文本显示为QTextEdit，就像在C的printf中一样

Question

I would like to display a double in qttextedit. For example, if i have

double f = 0.0;

and I do

ui.textEdit->insertPlainText("f = "+ QString::number(f ));

I get

f =0

I would like to show

f = 0.000

with as many decimal places as I want..

Anyway to do that..

Answer 1

I can not test it right now, but I would try ui.textEdit->insertPlainText(QString("f = %1").arg(f, 5, 'g', -1, QLatin1Char('0')));

See this for more details.

Answer 2

You have at least two Qt options:

1) QString & QString::sprintf ( const char * cformat, ... )

QString result;
double f = 0.000;
result.sprintf("%.3f", f);
ui.textEdit->insertPlainText(result);

2) QString QString::arg ( double a, int fieldWidth = 0, char format = 'g', int precision = -1, const QChar & fillChar = QLatin1Char( ' ' ) ) const

double f = 0.000;
QTextStream standardOutput(stdout);
standardOutput << QStringLiteral("f = %1").arg(f, 0, 'f', 3) << "\n";

Here you can find my test code that is easy to run in order to verify.

main.cpp

#include <QString>
#include <QTextStream>

int main()
{
    QString result;
    double f = 0.000;
    result.sprintf("%.3f", f);
    QTextStream standardOutput(stdout);
    standardOutput << QStringLiteral("f = %1").arg(f, 0, 'f', 3) << "\n";
    standardOutput << "f = " << result << "\n";
    return 0;
}

main.pro

TEMPLATE = app
TARGET = main
QT = core
SOURCES += main.cpp

Build and Run

qmake && make && ./main

Output

f = 0.000
f = 0.000