qt double转字符串保留指定位小数并去掉多余的0

分3步

1. 转保留n位小数字符串
2. 字符串转回double
3. 转字符串去掉多余0

QString::number(QString::asprintf("%.2f", number).toDouble(), 'f', QLocale::FloatingPointShortest);
//12 -> 12
//12.3 -> 12.3
//12.3456 -> 12.35