Every subclass of Fragment must be public and have a public, nullary constructor. The Android framework will reflectively instantiate them after a configuration change, such as screen rotation, and if the class is not instantiable by Class#newInstance(), an InstantiationException will be thrown.

In addition, it is strongly recommended that subclasses not have other constructors with parameters, since these constructors will not be called when the fragment is re-instantiated; instead, arguments should be supplied with setArguments(Bundle) and retrieved with getArguments().

For more information, please see the documentation for Fragment.

This check is an adaptation of the ValidFragment rule of Android Lint.