bottomNavigation：ReselectedListener：试图调用虚拟方法的空对象引用

Question

我使用底部的导航在我的布局，但是当我尝试在我的主要活动写一个关于点击它的onCreate它给了我一个例外：

试图在空对象上调用虚拟方法参考 private BottomNavigationView bottomNavigationView;

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_nav); 

    super.onCreate(savedInstanceState); 
    bottomNavigationView.setOnNavigationItemReselectedListener(new BottomNavigationView.OnNavigationItemReselectedListener() { 
     @Override 
     public void onNavigationItemReselected(@NonNull MenuItem item) { 

     } 
    }); 

Answer 1

改变这种

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

    bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_nav); 
    bottomNavigationView.setOnNavigationItemReselectedListener(new BottomNavigationView.OnNavigationItemReselectedListener() { 
     @Override 
     public void onNavigationItemReselected(@NonNull MenuItem item) { 

     } 
    });