我正在Android中使用Firestore。在我的片段中，我有一个recyclerview，可以从Firestore中获取数据，但是在首次启动应用程序时，recyclerview是空的，但是当我移至另一个片段并返回时，它会加载数据。
这是我的适配器类
public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.ViewHolder> {
private List<ProductPost> product_list;
FirebaseFirestore firebaseFirestore;
FirebaseAuth auth;
private TextView cartCount;
private Context context;
private int previousPosition = 0;
private int itemInCart;
//pass textview and value of item in cart to constructor
public RecyclerAdapter (Context context, List<ProductPost> product_list, TextView cartCount, int itemInCart){
this.cartCount = cartCount;
this.product_list = product_list;
this.itemInCart = itemInCart;
this.context = context;
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.single_main, parent, false);
context = parent.getContext();
firebaseFirestore = FirebaseFirestore.getInstance();
auth = FirebaseAuth.getInstance();
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull final ViewHolder holder, @SuppressLint("RecyclerView") int position) {
holder.setIsRecyclable(false);
final String productID = product_list.get(position).ProductID;
String image_uri = product_list.get(position).getImage();
holder.retrieveImage(image_uri);
//if user is authenticated, count number of document and attach the size to the view (floating button)
if(auth.getCurrentUser() != null){
final String currentUser = auth.getCurrentUser().getUid();
firebaseFirestore.collection(currentUser).get()
.addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
@Override
public void onComplete(@NonNull Task<QuerySnapshot> task) {
int count = 0;
for (final QueryDocumentSnapshot document : task.getResult()){
count += Integer.parseInt(document.getString("qty"));
cartCount.setText(Integer.toString(count));
}
}
});
}
holder.postImage.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(final View view) {
holder.bookProgress.setVisibility(View.VISIBLE);
firebaseFirestore.collection("All_Books").document(productID)
.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
@Override
public void onComplete(@NonNull Task<DocumentSnapshot> task) {
if(task.isSuccessful()){
DocumentSnapshot documentSnapshot = task.getResult();
if(documentSnapshot != null){
String display_price = documentSnapshot.getString("book_price");
String display_name = documentSnapshot.getString("Name");
String display_title = documentSnapshot.getString("book_title");
String display_category = documentSnapshot.getString("category");
String display_image = documentSnapshot.getString("image");
String display_store = documentSnapshot.getString("store_name");
String display_description = documentSnapshot.getString("description");
Intent intent = new Intent().setClass(view.getContext(), BookDetails.class);
intent.putExtra("price", display_price);
intent.putExtra("name", display_name);
intent.putExtra("title", display_title);
intent.putExtra("image", display_image);
intent.putExtra("store", display_store);
intent.putExtra("category", display_category);
intent.putExtra("desc", display_description);
intent.putExtra("product_id", productID);
view.getContext().startActivity(intent);
}else{
holder.bookProgress.setVisibility(View.INVISIBLE);
Toast.makeText(context, "This book is finished in the store!", Toast.LENGTH_LONG).show();
}
}else{
String error = Objects.requireNonNull(task.getException()).getMessage();
Toast.makeText(context, error, Toast.LENGTH_LONG).show();
holder.bookProgress.setVisibility(View.INVISIBLE);
}
}
});
}
});
}
@Override
public int getItemCount() {
return product_list.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
private View mview;
private ImageView postImage;
private ProgressBar bookProgress;
TextView mainText;
private ViewHolder(View itemView) {
super(itemView);
mview = itemView;
postImage = mview.findViewById(R.id.product);
bookProgress = mview.findViewById(R.id.bookProgress);
mainText = mview.findViewById(R.id.mainText);
}
private void retrieveImage(String downloadUri){
postImage = mview.findViewById(R.id.product);
Glide.with(context).load(downloadUri).listener(new RequestListener<Drawable>() {
@Override
public boolean onLoadFailed(@android.support.annotation.Nullable GlideException e, Object model, Target<Drawable> target, boolean isFirstResource) {
mainText.setVisibility(View.GONE);
return false;
}
@Override
public boolean onResourceReady(Drawable resource, Object model, Target<Drawable> target, DataSource dataSource, boolean isFirstResource) {
mainText.setVisibility(View.GONE);
return false;
}
})
.into(postImage);
}
}
}
我的片段类
Query.addSnapshotListener(new EventListener<QuerySnapshot>() {
@Override
public void onEvent(@Nullable QuerySnapshot queryDocumentSnapshots, @Nullable FirebaseFirestoreException e) {
if (e != null) {
return;
}
if(queryDocumentSnapshots != null && !queryDocumentSnapshots.isEmpty()){
for (DocumentChange doc : queryDocumentSnapshots.getDocumentChanges()) {
if (doc.getType() == DocumentChange.Type.ADDED) {
String productID = doc.getDocument().getId();
ProductPost productPost = doc.getDocument().toObject(ProductPost.class).withId(productID);
product_list.add(productPost);
productRecyclerAdapter.notifyDataSetChanged();
}
}
}
我希望片段在第一次启动时按预期加载。需要帮助...谢谢。
答案 0 :(得分：0)
您是第一次在哪里设置适配器的？因为您应该在列表中获得元素后执行此操作
if (doc.getType() == DocumentChange.Type.ADDED) {
String productID = doc.getDocument().getId();
ProductPost productPost = doc.getDocument().toObject(ProductPost.class).withId(productID);
product_list.add(productPost);
//set your adapter here first
productRecyclerAdapter.notifyDataSetChanged();
}