Android Studio Project Main.java public class Main extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener { private DrawerLayout mDrawerLayout ; ExpandableListAdapter mMenuAdapter ; ExpandableListView expandableList ; List<ExpandedMenuModel> listDataHeader ; HashMap<ExpandedMenuModel, List<String>> listDataChild ; @Override protected void onCreate(Bundle savedInstanceState) { super .onCreate(savedInstanceState); setContentView(R.layout. main ); Toolbar toolbar = (Toolbar) findViewById(R.id. toolbar ); // Toolbar Action setSupportActionBar(toolbar); FloatingActionButton fab = (FloatingActionButton) findViewById(R.id. fab ); fab.setOnClickListener( new View.OnClickListener() { @Override public void onClick(View view) { Snackbar. make (view, "Replace with your own action" , Snackbar. LENG...