I have an app wich litterally have only one setting : turn the contextual help on or off
I am tempted to put this settings in the navigation drawer, with a simple on/off switch.
Is it the right place to put this setting ?
Should I create a setting screen with only one setting ?
If the default is to show the contextual help and then you give the user the option to turn the help off then the first option "put this settings in the navigation drawer, with a simple on/off switch" should work very well. The user was aware that there was contextual help and turned it off.
If you want to go one extra step, after the user selects "turn off contextual help" you can run a little animation that shows the user where he can find it again in order to turn it back on.
All the above is based on the assumption that the user will not want to flip back and forth turning on contextual help; then turning it off; then turning it back on.
I wouldn't create an entire Settings-view, just for a single Switch. Also, placing it in the navigation drawer is a strange place to put it (atleast, I've never seen it before).
If it is possible for your app, and it is clear enough for your users, you could consider placing the Switch in the Actionbar.
