無法在片段中設置RecycleView適配器

Question

我有這樣的片段

...

public class Dashboard extends Fragment{
    private RecyclerView mTopSellersListView;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.main_dashboard, container, false);
        mTopSellersListView = (RecyclerView) view.findViewById(R.id.topSellersListView);
        return view;
    }

    public void setTopSellersListView(MyRecycleAdapter adapter){
        mTopSellersListView.setHasFixedSize(true);
        mTopSellersListView.setAdapter(adapter);
        mTopSellersListView.setLayoutManager(new LinearLayoutManager(getActivity()));
        mTopSellersListView.addItemDecoration(new DividerItemDecoration(getActivity(), LinearLayoutManager.VERTICAL));
        mTopSellersListView.setItemAnimator(new DefaultItemAnimator());
    }
}

我總共有4個片段，可以使用此方法通過底部欄在MainActivity中切換所有片段，當用戶點擊菜單時，它將用另一個片段替換當前片段（默認值：儀表板）：

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mDashboardFragment = new Dashboard();
        mOrdersFragment = new Orders();
        mProductsFragment = new Products();
        mSettingFragment = new Setting();
        settingMenu(savedInstanceState);
}

...

public void selectMenu(String menu){
    Fragment fr = null;
    switch (menu) {
        case "Dashboard":
            fr = mDashboardFragment;
            break;
        case "Orders":
            fr = mOrdersFragment;
            break;
        case "Products":
            fr = mProductsFragment;
            break;
        case "Setting":
            fr = mSettingFragment;
            break;
    }
    FragmentManager fm = getFragmentManager();
    FragmentTransaction fragmentTransaction = fm.beginTransaction();
    fragmentTransaction.replace(R.id.fragment, fr);
    fragmentTransaction.addToBackStack(null);
    fragmentTransaction.commit();
}

我在另一個類（不是活動類）中訪問setTopSellersListView（）

MainActivity.mDashboardFragment.setTopSellersListView(mProductAdapter);

並在mTopSellersListView.setHasFixedSize（true）處獲得了NullPointerExceptions

Answer 1

首先設置您的layoutManager而不是使用setHasFizedSize（true）。因為layoutManager決定了recyclerView的大小。

Answer 2

我已經通過在Fragment的onStart（）中調用setTopSellersListView（）修復了它，並且效果很好