QDial：如何将 int 值传递给需要 const char* 的 Qfile？

Question

Problem is already described in title: I'm using a QDial to set contrast level of a LCD 7" display (connected to an embedded Linux Single Board Computer).

Simple way to do this is to send on terminal an "echo" instruction. I send it as a QFile:

QFile ContrLCD("/sys/class/backlight/backlight/brightness");

and I need to send the level writing in this QFile

ContrLCD.write("number");

Problem is QDial manage int variable, while QFile requires const char* to send number corresponding to contrast.

How to do this?

Answer 1

BacklightController::setBrightness(int brightness) // slot
{
    QFile f{"/sys/class/backlight/backlight/brightness"};
    if (!f.open(QIODevice::WriteOnly)) return;
    QTextStream stream{&f};
    stream << brightness;
}

Answer 2

This example is taken from the documentation for QFile :

 QFile file("out.txt"); if (!file.open(QIODevice::WriteOnly | QIODevice::Text)) return; QTextStream out(&file); out << "The magic number is: " << 49 << "\\n";

Seems like you can use a QTextStream to write formatted output to a QFile . I did not use it myself, so there might be other ways, but for formatted output of numbers this seems to be the right tool.