Technique to Avoid, #2: Directly Manipulating Settings
Strictly speaking this one isn't evil, since this is a change in behavior that we made to Android itself. But we made it because some developers were doing naughty things: a number of apps were changing system settings silently without even notifying the user. For instance, some apps turn on GPS without asking the user, and others might turn on data roaming.
As a result, applications can no longer directly manipulate the values of certain system Settings, even if they previously had permission to do so. For instance, apps can no longer directly turn on or off GPS. These apps won't crash, but the APIs in question now have no effect, and do nothing. Instead, apps will need to issue an Intent to launch the appropriate Settings configuration screen, so that the user can change these settings manually. For details, see the android.provider.Settings.Secure class, which you can find in the 1.5_pre SDK documentation (and later). Note that only Settings that were moved to the Settings.Secure class are affected. Other, less sensitive, settings will continue to have the same behavior as in Android 1.1.