import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.preference.PreferenceManager;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.preference.PreferenceManager;
public class PreferenceActivity extends AppCompatActivity
implements SharedPreferences.OnSharedPreferenceChangeListener {
public class PreferenceActivity extends AppCompatActivity
implements SharedPreferences.OnSharedPreferenceChangeListener {