输出除法结果，包括小数点后的数字-Qt

Question

I am sorry if it's already answered in here, but I couldn't find the exact solution I am looking for.

I am trying to output the result of a division of two variable which is continuously changing. The result may vary from 0.00 to 100.12314235234523 (not exactly this specific, I just wanted to give you an idea). I want to print the result only 2 digits after the decimal point, if there is nothing after decimal, it should print 2 zeroes after decimal.

For example:

10 / 5 = 2.00

23 / 6 = 3.83

I don't need to round up the result for example, if the output is: 73.4869999, I don't need it to be 73.49, 73.48 is fine with me.

What I have written so far is:

packet_loss[2]->setText(QString("%1%2%3").arg(((data.packet_loss_tx) * 100) / data.packets_tx).
                                          arg(locale.decimalPoint()).
                                          arg((((data.packet_loss_tx) * 100) % data.packets_tx), 2, 10, QChar('0')));

But this prints all the values after the decimal point. I can divide this part arg((((data.packet_loss_tx) * 100) % data.packets_tx) with 10, 100 or 1000 to reduce the number of decimals after the decimal point but this is a variable which changes every seconds. So if the output is 3 digits after decimal and I divide it by 10, I will get proper output, but the next value may be 5 digits after decimal and division by 10 will give me 4 digits after decimal. I want the final output to show only 2 digits after decimal.

Answer 1

You could try to use QString::number() function with specific formatting options (two digits precision). For example:

auto s = QString::number(100.12914235234523, 'f', 2); // Gives "100.13"

Besides, if you use floating point numbers, it's better to multiply them with floating point numbers too. Ie you need to perform your calculations using 100.0 instead of integer value 100.