我最终使用了下面两个函数来解决这个问题。在这里发布，以防将来其他人也有类似的问题。
browseFragment是Fragment类中的示例变量，这些方法是该类的一部分。

private final int maxHookIntoFocusTries = 5;
private int hookIntoFocusTries = 0;

private void initFocusManagement() {
    View view = browseFragment.getView();
    Handler handler = new Handler();
    if(view == null){
        //Wait for the view to be added
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                initFocusManagement();
            }
        };
        handler.postDelayed(runnable, 250);
    }
    if ( view instanceof ViewGroup) {
        boolean found = hookIntoFocusSearch((ViewGroup) view);
        if ( found ){
            Timber.d("Successfully fixed focus");   //This is just a log
        }else if(hookIntoFocusTries < maxHookIntoFocusTries){
            //Allow multiple attempts to hook into the focus system
            //I want to say this was needed for when the browse fragment was
            //created but the child content hadn't been populated yet.
            //Been a while since I've messed with this code though
            hookIntoFocusTries++;
            handler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    initFocusManagement();
                }
            }, 250);
        }
    }

}

private boolean hookIntoFocusSearch(ViewGroup vg) {
    boolean found = false;
    for ( int i=0; i<vg.getChildCount(); i++ ) {
        View view = vg.getChildAt(i);
        if ( view instanceof BrowseFrameLayout) {
            BrowseFrameLayout bfl = (BrowseFrameLayout)view;
            bfl.setOnFocusSearchListener(new BrowseFrameLayout.OnFocusSearchListener() {
                @Override
                public View onFocusSearch(View focused, int direction) {
                    if ( direction == View.FOCUS_UP ) {
                        return searchButton;
                    } else {
                        return null;
                    }
                }
            });
            found = true;
            break;
        } else if ( view instanceof ViewGroup ) {
            boolean foundInRecurse = hookIntoFocusSearch((ViewGroup)view);
            if ( foundInRecurse ) {
                found = true;
                break;
            }
        }
    }
    return found;
}

编辑：更新代码以包含重试处理程序

我也有过和你一样的问题，受你的代码启发，我做了一些调整。
在我扩展的BrowseFragment中，我有这个方法：

public void workaroundFocus(){
    if(getView() != null) {
        View viewToFocus  = getActivity().findViewById(R.id.view_to_focus);
        BrowseFrameLayout browseFrameLayout = getView().findViewById(android.support.v17.leanback.R.id.browse_frame);
        browseFrameLayout.setOnFocusSearchListener((focused, direction) -> {
            if (direction == View.FOCUS_UP) {
                return viewToFocus;
            }
            else {
                return null;
            }
        });
    }
}

然后：

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    workaroundFocus();
    /*
      Rest of code
    */
}

这样就不需要使用处理程序和计时器。

- I was also facing the same issue as I was not able to navigate from Left to right but when I press the Right arrow button but the focus moved to downside views instead of right side views. 

 - I achieve it using setOnKeyListener and the code snipped as mentioned below:

 - in the below, img_mygame is in focus and I want to move focus to the right side which is img_controller.

 
 img_mygame.setOnKeyListener((view, keyCode, event) -> {
            if (keyCode == KeyEvent.KEYCODE_DPAD_RIGHT) {
                img_controller.requestFocus();
                img_mygame.setNextFocusRightId(R.id.img_controller);
                return true;
            }

            return false;
        });