<fragment android:name="com.example.android.quakereport.SettingsActivity$EarthquakePreferenceFragment" . . . </fragment>
Here, the (SettingActivity) and the (EarthquakePreferenceFragment) are any classes in java.
Can anyone tell me what is the use if $ in here ???
It means an inner static class. In your example it would be as next:
public class SettingsActivity extends AppCompatActivity {
.... other activity code ....
// Inner class
public static class EarthquakePreferenceFragment extends Fragment {
.......
}
}