Question

ProgressBar不会在片段中消失，也不会在RecyclerView中加载项目，当代码位于主要活动的onCreate主体中时，它就可以工作

我正在制作包含ProgressBar和RecyclerView的片段，并从firebase数据库中检索数据，我在onDataChange方法的末尾添加了setVisibility，以便在获取所有数据并将其存储在数组列表中之后，ProgressBar消失

RecyclerView offersRecycler;
ArrayList<offer> offers;

OffersAdapter offersAdapter;

View fragment_layout;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    fragment_layout = inflater.inflate(R.layout.fragment_offers, container, false);

    // Offers RecyclerView
            offersRecycler = fragment_layout.findViewById(R.id.offersRecycler);
            offers = new ArrayList();
            offers_init();
            offersAdapter = new OffersAdapter(offers,getContext());
            offersRecycler.setAdapter(offersAdapter);
            offersRecycler.setLayoutManager(new LinearLayoutManager(getContext()));


    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_offers, container, false);
}


private void offers_init() {
    DatabaseReference db_offers = db_ref().child("offers");

    db_offers.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            try {
                ProgressBar loadingOffers = fragment_layout.findViewById(R.id.loadingOffers);
                loadingOffers.setProgress(10);

                for (DataSnapshot offer_item : dataSnapshot.getChildren()) {

                    String id = offer_item.getKey();
                    String title = offer_item.child("title").getValue().toString();
                    String rating = offer_item.child("rating").getValue().toString();
                    String orders_number = offer_item.child("orders_number").getValue().toString();

                    offer offer_object = new offer(id,title, rating, orders_number);
                    offers.add(offer_object);

                    offersAdapter.notifyDataSetChanged();
                }

                Toast.makeText(getContext(),"title",Toast.LENGTH_LONG).show();
                loadingOffers.setVisibility(View.GONE);

            }catch (Exception ex){
                Toast.makeText(getContext(),ex.getMessage(),Toast.LENGTH_LONG).show();
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {}
    });



}

我希望ProgressBar隐藏并且将数组加载到RecyclerView

Answer 1

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                     Bundle savedInstanceState) {

fragment_layout = inflater.inflate(R.layout.fragment_offers, container, false);

// Offers RecyclerView
        offersRecycler = fragment_layout.findViewById(R.id.offersRecycler);
        offers = new ArrayList();
        offers_init();
        offersAdapter = new OffersAdapter(offers,getContext());
        offersRecycler.setAdapter(offersAdapter);
        offersRecycler.setLayoutManager(new LinearLayoutManager(getContext()));


// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_offers, container, false);
}

^这是您的代码段。您正在做的是-扩大布局fragment_layout = inflater.inflate(R.layout.fragment_offers, container, false)并使用fragment_layout获取RecyclerView的实例。很好。

但是在方法的最后，您要膨胀一个新的布局并返回它。因此，Android框架使用该View而不是fragment_layout来设置Fragment视图。 fragment_layout中的所有视图都不会显示，因为它从未添加到片段中，因此您在RecyclerView中看不到任何更改。

在onCreateView方法的末尾，您应该只返回fragment_layout。

Answer 2

在您的CreateView中，更改

return inflater.inflate(R.layout.fragment_offers, container, false);

作者

return fragment_layout;

您将布局称为init recyclerview，但调用了“空白”布局

此外，请避免在方法或变量名下加下划线，这不是Java约定

为什么片段中的setVisibility不起作用？

2 个答案: