领券联盟主Activity实现fragment，我在新BActivity中也复制了一样的方法实现fragment，新创建了intent跳转想要从B跳转到A显示，但是一直报错空指针。

public class RealMainAc extends AppCompatActivity  {



    @BindView(R.id.real_main_navigation_bar)
    public BottomNavigationView mNavigationView;

    private Button reserve;
    private Button button;

    private RealHomeFragment rRealHomeFragment;
    private RecommendFragment rRecommendFragment;
    private MessageFragment rMessageFragment;
    private UserFragment rUserFragment;
    private Unbinder rBind;

    private FragmentManager rFm;
    // private final String tag = "";


    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (rBind!=null) {
            rBind.unbind();
        }


    }

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

        rBind = ButterKnife.bind(this);
        reserve =(Button) findViewById(R.id.reservation);
        button = (Button) findViewById(R.id.button2) ;
         initListener();
         initFragment();
        //reserve.setOnClickListener(this);



    }





    private void initFragment() {
        rRealHomeFragment = new RealHomeFragment();
        rRecommendFragment = new RecommendFragment();
        rMessageFragment = new MessageFragment();
        rUserFragment  = new UserFragment();
        rFm = getSupportFragmentManager();
        switchFragment(rRealHomeFragment);


    }

    //  private void initView(){

    //    HomeFragment homeFragment = new HomeFragment();
    //    mfm= getSupportFragmentManager();
    //   FragmentTransaction transaction = mfm.beginTransaction();
    //   transaction.add(R.id.main_page_container,homeFragment);

    // transaction.commit();

// }



    private  void initListener(){
        mNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(  @Nullable MenuItem item) {

                if(item.getItemId() == R.id.real_home){
                    //Log.d(tag,"切换到首页");
                    LogUtils.d(this,"切换到首页");
                    switchFragment(rRealHomeFragment);
                }else if(item.getItemId() == R.id.real_select){
                    LogUtils.i(this,"切换到推荐");
                    switchFragment(rRecommendFragment);
                }else if(item.getItemId() == R.id.real_message){
                    LogUtils.d(this,"切换到消息");
                    switchFragment(rMessageFragment);
                }else if(item.getItemId() == R.id.real_search){
                    LogUtils.d(this,"切换到搜索");
                    switchFragment(rUserFragment);
                }

                return true;
            }
        });
        reserve.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick( View v) {

                Intent intent = new Intent( RealMainAc.this,ui.activity.RealMainAc.class); //跳转到页面1
                startActivity(intent);
            }
        });
    }

    private void switchFragment(BaseFragment targetFragment) {
        FragmentTransaction fragmentTransaction= rFm.beginTransaction();
        fragmentTransaction.replace(R.id.real_home_container,targetFragment);
        fragmentTransaction.commit();

    }



}

报错空指针