java.lang.IllegalStateException: Required view 'nav' with ID 2131558567 for field

java.lang.IllegalStateException: Required view 'nav' with ID 2131558567 for field 'mAHBottomNavigation' was not found. If this view is optional add '@Nullable' (fields) or '@Optional' (methods) annotation.

原因：BaseActivity忘记加这一行：this.setContentView(this.getLayoutId());

    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        // 设置不能横屏，防止生命周期的改变        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_NOSENSOR);        this.setContentView(this.getLayoutId());//缺少这一行        ButterKnife.bind(this);//绑定ButterKnife        mContext = this;        this.initView();        this.initData();        this.initEvent();        Timber.tag(TAG).i("-->onCreate()");    }    /**     * 获取布局id     *     * @return     */    protected abstract int getLayoutId();