使用导航抽屉与其他活动

我如何选择当我正在进行一项活动时，再次按下按钮上的抽屉，让我进入同一活动时，它将关闭抽屉？ 有任何选项可以检查我现在是否在特定活动中？ 这是我的抽屉主页：

公共类Main_Page扩展AppCompatActivity实现NavigationView.OnNavigationItemSelectedListener {

@Override保护无效onCreate（Bundle savedInstanceState）{

super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main__page);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
        this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();

NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);

}

@Override public void onBackPressed（）{DrawerLayout drawer =（DrawerLayout）findViewById（R.id.drawer_layout）; （drawer.isDrawerOpen（GravityCompat.START））{drawer.closeDrawer（GravityCompat.START）; } else {super.onBackPressed（）; }

}

@SuppressWarnings（“StatementWithEmptyBody”）@Override public boolean onNavigationItemSelected（MenuItem item）{Intent Home = new Intent（Main_Page.this，Main_Page.class）; 意图设置=新意图（Main_Page.this，Settings.class）; int id = item.getItemId（）;

if (id == R.id.Main_App)
    startActivity(Home);
else if (id== R.id.nav_Settings)
    startActivity(Settings);
else if (id == R.id.Nav_Log_Out) {
            super.onBackPressed();
}

DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;

}}