我的数据来自 FireStore 到一个自定义类对象中，当我用一个 Toast 在for循环中，我可以显示所有我想要的数据，但我传递给适配器的列表是空的。
我试着找出它是空的原因，但没有任何效果。
这是我的主类，我的适配器类是这样的：
products.whereEqualTo("IDliv","kITQ8wiPshsnWqHDlP5D").addSnapshotListener(new EventListener<QuerySnapshot>() {
@Override
public void onEvent(@Nullable QuerySnapshot documentSnapshots, @Nullable FirebaseFirestoreException e) {
assert documentSnapshots != null;
for (DocumentChange document : documentSnapshots.getDocumentChanges()) {
generalObject obj=document.getDocument().toObject(generalObject.class);
for(int i=0;i<obj.getproducts().size();i++){
String[] body;
body=obj.getproducts().get(i).toString().split("\\+");
ProductModel p = new ProductModel(body[0].toString(), body[1].toString(), body[2].toString());
prod.add(p);
}
}
}
});
if(prod.size()>0) {
adapter = new ProductAdapter(prod);
RecyclerView recview = findViewById(R.id.items_recycler_view);
recview.setHasFixedSize(true);
recview.setLayoutManager(new LinearLayoutManager(this));
recview.setAdapter(adapter);
}else{
Toast.makeText(getApplicationContext(),"this list is empty",Toast.LENGTH_LONG).show();
}
}
而我的适配器类是这样的:
public class ProductAdapter extends RecyclerView.Adapter<ProductAdapter.ViewHolder> {
private ArrayList<ProductModel> products;
public ProductAdapter(ArrayList<ProductModel> product) {
this.products = product;
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View v = (View) LayoutInflater.from(parent.getContext()).inflate(R.layout.adapter_product, parent, false);
return new ViewHolder(v);
}
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
ProductModel prod = products.get(position);
holder.name.setText(prod.getGetProductName());
holder.description.setText(prod.getProductMarque());
holder.qty.setText(prod.getProductQte());
}
@Override
public int getItemCount() {
if (products != null) {
return products.size();
} else {
return 0;
}
}
public static class ViewHolder extends RecyclerView.ViewHolder {
public final View view;
public final TextView name;
public final TextView description;
public final TextView qty;
public ViewHolder(View view) {
super(view);
this.view = view;
name = view.findViewById(R.id.productsName);
description = view.findViewById(R.id.marque);
qty=view.findViewById(R.id.quantity);
}
}
}
你知道是什么问题吗？
你需要添加 notifyDataSetChanged() 时，事件回调结束。
@Override
public void onEvent(@Nullable QuerySnapshot documentSnapshots, @Nullable FirebaseFirestoreException e) {
assert documentSnapshots != null;
for (DocumentChange document : documentSnapshots.getDocumentChanges()) {
generalObject obj=document.getDocument().toObject(generalObject.class);
for(int i=0;i<obj.getproducts().size();i++){
String[] body;
body=obj.getproducts().get(i).toString().split("\\+");
ProductModel p = new ProductModel(body[0].toString(), body[1].toString(), body[2].toString());
prod.add(p);
}
adapter.notifyDataSetChanged(); // <<<<<< here is the change
}
另一件事： if(prod.size()>0) 条件太早了，因为它不会匹配，因为数据是在后台线程上接收的，所以这个条件永远不会满足。把这部分改成。
adapter = new ProductAdapter(prod);
RecyclerView recview = findViewById(R.id.items_recycler_view);
recview.setHasFixedSize(true);
recview.setLayoutManager(new LinearLayoutManager(this));
recview.setAdapter(adapter);
if (prod.size()==0) {
Toast.makeText(getApplicationContext(),"this list is empty",Toast.LENGTH_LONG).show();
}
你从Firebase发出的查询是异步进行的 所以在你实例化适配器后，查询数据就会回来并被添加到产品列表中了
你的if语句没有被满足，因为产品列表实际上是空的，因为那段代码在查询返回之前被执行了。
// This is false here because this block is getting executed before
// the Firebase query returns the data. However your not seeing the
// toast, because you are passing the wrong context. Toast takes
// an activity context, not application context.
if(prod.size()>0) {
adapter = new ProductAdapter(prod);
RecyclerView recview = findViewById(R.id.items_recycler_view);
recview.setHasFixedSize(true);
recview.setLayoutManager(new LinearLayoutManager(this));
recview.setAdapter(adapter);
}else{
Toast.makeText(getApplicationContext(),"this list is empty",Toast.LENGTH_LONG).show();
}
试着修改一下你的代码来创建适配器，然后在查询返回后再添加数据。
adapter = new ProductAdapter();
RecyclerView recview = findViewById(R.id.items_recycler_view);
recview.setHasFixedSize(true);
recview.setLayoutManager(new LinearLayoutManager(this));
recview.setAdapter(adapter);
products.whereEqualTo("IDliv","kITQ8wiPshsnWqHDlP5D").addSnapshotListener(new EventListener<QuerySnapshot>() {
@Override
public void onEvent(@Nullable QuerySnapshot documentSnapshots, @Nullable FirebaseFirestoreException e) {
assert documentSnapshots != null;
for (DocumentChange document : documentSnapshots.getDocumentChanges()) {
generalObject obj=document.getDocument().toObject(generalObject.class);
for(int i=0;i<obj.getproducts().size();i++){
String[] body;
body=obj.getproducts().get(i).toString().split("\\+");
ProductModel p = new ProductModel(body[0].toString(), body[1].toString(), body[2].toString());
prodList.add(p);
}
// Tell the adapter we have new data that we want to add
adapter.addNewData(prodList)
}
}
});
然后稍微修改一下你的适配器
public class ProductAdapter extends RecyclerView.Adapter<ProductAdapter.ViewHolder> {
private ArrayList<ProductModel> products;
public ProductAdapter() {
this.products = new ArrayList<ProductModel>();
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View v = (View) LayoutInflater.from(parent.getContext()).inflate(R.layout.adapter_product, parent, false);
return new ViewHolder(v);
}
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
ProductModel prod = products.get(position);
holder.name.setText(prod.getGetProductName());
holder.description.setText(prod.getProductMarque());
holder.qty.setText(prod.getProductQte());
}
@Override
public int getItemCount() {
if (products != null) {
return products.size();
} else {
return 0;
}
}
public void addNewData(data: List<ProductModel>) {
this.products.clear();
this.products.addAll(data);
notifyDatasetChanged(); //This will tell the adapter we have new data and to re-inflate the views
}
}