空对象引用上的'void android.support.v4.widget.DrawerLayout.addDrawerListener（android.support.v4.widget.DrawerLayout $ DrawerListener）'

Question

我正在为我的应用程序创建一个导航栏，然后我在这里遇到这个问题，有人可以告诉我在哪里修复它吗？我是新来的！！ 我已经从布局到mainactivity设置了相同的ID，但是没有用

在空对象引用上'避免android.support.v4.widget.DrawerLayout.addDrawerListener（android.support.v4.widget.DrawerLayout $ DrawerListener）'

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //NavigationBar

    drawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
    actionBarDrawerToggle = new ActionBarDrawerToggle(this,drawerLayout,R.string.Open,R.string.Close);
    actionBarDrawerToggle.setDrawerIndicatorEnabled(true);


    drawerLayout.addDrawerListener(actionBarDrawerToggle);
    actionBarDrawerToggle.syncState();

    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    final NavigationView navView = (NavigationView)findViewById(R.id.nav_view);
    navView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
        @Override public boolean onNavigationItemSelected(@NonNull MenuItem item)
        {
            int  id = item.getItemId();

            if ( id == R.id.huongdan)
            {
                Toast.makeText(MainActivity.this,"Coming soon", Toast.LENGTH_SHORT).show();

            }
            else if ( id == R.id.banggia)
            {
                Toast.makeText(MainActivity.this,"Coming soon", Toast.LENGTH_SHORT).show();

            }
            else if ( id == R.id.thongtin)
            {
                Toast.makeText(MainActivity.this,"Coming soon", Toast.LENGTH_SHORT).show();

            }



            return true;
        }
    });