I am working on a Qt application running on embedded Linux. I am pretty new to this Qt business since I have just started it a month back, so understand that I'm not that object-oriented ... :P
I have the Qt applications running on my target running Linux. The Qt documentation http://doc.qt.io/archives/qt-4.7/qt-embedded-pointer.html says that we have to enable touchscreen, USB keyboard, keypad, etc. by exporting certain variables. Namely,
export QWS_MOUSE_PROTO=tslib:/dev/input/event1
export QWS_KEYBOARD="linuxinput:/dev/input/event0 usb:/dev/input/event2"
well, as you can guess, first line sets the mouse device in QT as touchscreen. "tslib" is the touchscreen library, and the "event1" is the node representing the touchscreen. Similarly, second line is for on-board keypad (event0), and USB keyboard (event2).
Now, the touchscreen work very well. But the problem is with either keyboard. If I do not export the second variable, namely QWS_KEYBOARD , then the application runs fine. But if I do export the second variable, the application goes into stopped state (SIGSTOP) as soon as it is launched. This is evident from ps output. I can not make it work with SIGCONT.
I am going to try and reconfigure Qt from source. Any thoughts are welcome.
Can not believe this but setting the QWS_KEYBOARD variable as null solved the problem. Found it in the Qt developer FAQ http://developer.qt.nokia.com/faq/answer/why_doesnt_my_keyboard_work_after_i_have_done_an_export_qws_keyboard_dev_tt
export QWS_KEYBOARD=""
Well, it did not completely solve the problem since I still have to include the native keypad along with the USB keyboard.
Anyway, I am able to move to fields using the arrow/TAB keys. Text input works well. Although CAPS-LOCK and NUM-LOCK do not seem to work. SHIFT works. I am able to terminate the application by Ctrl+Alt+Bkspce. So, for the time being, I am able to input text at least.
Will post if any improvements.
来源：https://stackoverflow.com/questions/7471951/keyboard-input-in-qt