Android中的刷新片段

Question

我有一个在应用程序启动时不包含任何内容的片段，但在加载数据后，它应该显示加载的数据。我在实现 DataLoadedListener 的函数 onDataLoaded 中的 MainActivity 中加载所有数据。加载数据后，函数通过函数调用 (initializeAdapter()) 将数据 (ArrayList) 作为参数发送。然后，函数 initializeAdapter() 获取它并初始化定制的适配器（适配器是一个全局对象，在 initializeAdapter() 中初始化并在 onCreateView() 中使用）。

我想我应该在数据加载完毕并初始化适配器之后刷新片段视图，但我不知道该怎么做。我尝试了很多方法，但都没有成功。

MainActivity中调用initializeAdapter()的onDataLoaded函数

    @Override
    public void onDataLoaded(List<Grad> gradovi, List<Ponuda> ponude) {

    Spinner spinnerGradovi = (Spinner) findViewById(R.id.gradovi_spinner);
    ArrayAdapter<String> adapterGradovi;
    List<String> listaGradova = new ArrayList<>();
    ArrayList<Ponuda> ponudaArrayList = new ArrayList<Ponuda>();

    ponudaLista = ponude;
    gradLista = gradovi;

    for(Grad grad : gradovi ){
        listaGradova.add(grad.getNaziv());
    }

    for(Ponuda ponuda : ponude){
        ponudaArrayList.add(ponuda);
    }


    adapterGradovi = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, listaGradova);

    spinnerGradovi.setAdapter(adapterGradovi);

    Fragment fragmentGet = svePonudeFragment;

    ((SvePonudeFragment)fragmentGet).initializeAdapter(ponudaArrayList);
}

这是一个片段

public class SvePonudeFragment extends Fragment {

private RecyclerView rv;
RVAdapter adapter;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.sve_ponude_fragment, container, false);

    rv = (RecyclerView) rootView.findViewById(R.id.rv);

    LinearLayoutManager llm = new LinearLayoutManager(getActivity());
    rv.setLayoutManager(llm);

    rv.setAdapter(adapter);

    return rootView;
}


public void initializeAdapter(List<Ponuda> preuzetePonude){

    adapter = new RVAdapter(preuzetePonude);

    //this isn't working
    /*FragmentManager manager = getActivity().getSupportFragmentManager();
    android.support.v4.app.FragmentTransaction ft = manager.beginTransaction();
    ft.detach(this).attach(this).commit();*/

    //this is not working, neither
    Fragment frg = getFragmentManager().findFragmentByTag("sve_ponude_fragment_tag");
    final android.support.v4.app.FragmentTransaction ft = getFragmentManager().beginTransaction();
    ft.detach(frg);
    ft.attach(frg);
    ft.commit();
}

}

我也对如何制作一个空的适配器感兴趣，如果数据还没有加载，它会加载？并且在加载数据时填写另一个适配器并使用它。

Answer 1

在设置之前初始化适配器。如果你有兴趣改变你的方法，我可以给出建议：为你的片段创建一个构造函数，你可以传递 ArrayList。 OnCreate 或 OnCreateView 您可以初始化适配器并将列表传递到其中。在设置适配器 notifyDataChanges 并检查是否有数据后，请在传递数据时和传递数据之前使用一些 Logs。不要直接责怪适配器或片段控制你的数据。此外，我建议您使用 Fragments + RecyclerView 进行更多研究。我发布了一个您可以查看的示例，但数据会加载到片段中。

public class CategoryFragment extends Fragment {

//Class Tag
private static final String TAG = CategoryFragment.class.getSimpleName();
//Fragments base context
private Context mContext;
//RecyclerView widget
private RecyclerView mRecyclerView;
//RecyclerView's Layout Manager
private RecyclerView.LayoutManager mLayourManager;
//RecyclerView's Adapter
private CategoryFragmentAdapter mCategoryFragmentAdapter;
//Category Data List
private ArrayList<Category> mCategoryList;
//Interface object
onCategoryItemClick mCallBackCategory;

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    //Instantiate base context
    mContext = context;
    //Instantiate interface
    mCallBackCategory = (onCategoryItemClick)getActivity();
}

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //Instantiate Category List
    mCategoryList = new ArrayList<Category>();
}

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    super.onCreateView(inflater, container, savedInstanceState);
    //Custom fragment view instantiating
    View view_fragment_category = inflater.inflate(R.layout.fragment_items, container, false);
    //Instantiating Fragment's recycler view
    mRecyclerView = (RecyclerView) view_fragment_category.findViewById(R.id.recycle_categories);
    //Instantiate RecycleView's Layout Manager: LinearLayoutManager is one of the default
    mLayourManager = new LinearLayoutManager(mContext);
    //Setting layout manager for recycler view
    mRecyclerView.setLayoutManager(mLayourManager);
    //Retrieve data from server, populate the category data list and set the RecyclerView's adapter
    getCategories();
    //Instantiate the adapter and push the data
    mCategoryFragmentAdapter = new CategoryFragmentAdapter(mContext, mCategoryList);

    //RecyclerView item click listener
    mCategoryFragmentAdapter.SetOnItemClickListener(new CategoryFragmentAdapter.OnItemClickListener() {

        @Override
        public void onItemClick(View v , int position) {
            //Test display
            //Toast.makeText(mContext, mCategoryList.get(position).getId(),Toast.LENGTH_LONG).show();

            //Push to Activity method with clicked item ID
            mCallBackCategory.proceedToProducts(mCategoryList.get(position).getId());

        }
    });

    return view_fragment_category;
}