QString格式化的几种用法：补零/进制转换/保留小数位等

QString QString::arg(long a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char(' ')) const

QString QString::arg(int a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char(' ')) const

1、QString格式化arg前面自动补0

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int seconds = m_calc.elapsed() / 1000;
int hour = int(seconds / 3600);
int min = int((seconds - hour * 3600) / 60);
int sec = seconds % 60;

//QString格式化arg前面自动补0
QString str = QString("%1:%2:%3").arg(hour, 2, 10, QLatin1Char('0')).arg(min, 2, 10, QLatin1Char('0')).arg(sec, 2, 10, QLatin1Char('0'));
QStringList list;
list << tr("%1").arg(hour) << tr("%1").arg(min) << tr("%1").arg(sec);

int val = 16;
//0f
QString str = QString("%1").arg(val & 0xFF, 2, 16, QLatin1Char('0'));

//0016
QString str = QString("%1").arg(val, 4, 10, QLatin1Char('0'));
//4代表宽度，10表示10进制，空位补零

2、进制转换

1 2	QString ss = QString("十进制64转为十六进制%1").arg(64, 0, 16); //0代表宽度，16表示16进制，空位补零

3、数字转QString，并保留小数点位数

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//整数转QString
int num1=123;
QString str1 = QString::number(num1);
qDebug()<<"str1:"<<str1<<endl;

//小数转QString,保留两位小数
double num2 = 123.456789;
QString str2=QString::number(num2,'f',2);
qDebug()<<"str2:"<<str2<<endl;

4、数字转QString，使用asprintf

1 2	ui->comboBox_pulse->addItem(QString::asprintf("%d", PULSE_LOW)); ui->lineEdit_x->setText(QString::asprintf("%.3f", m_stuMotionPos.X));

5、QString中的arg还可以对浮点类型的数字按照一定的精度来转换

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

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Format Meaning
e format as [-]9.9e[+|-]999
E format as [-]9.9E[+|-]999
f format as [-]9.9
g use e or f format, whichever is the most concise
G use E or f format, whichever is the most concise

QString ss = QString("delta %1").arg(123.45678, 0, 'g', 6);

结果是ss="delta 123.456"。浮点类型格式化为只显示六位有效数字，并且是采用四舍五入的方式。

6、QString/string/wstring的转换

QString::fromStdString()

QString::fromStdWString()

str.toStdString()

QObject::tr("位置超出范围").toStdWString()