如何查询集合以获取特定文档? [英] How to query a collection to get specific documents?
问题描述
我将通过一个示例开始解释我的问题，我有两个名为Users and Foods的根集合.在用户"集合中，包含带有用户信息(例如名称，图像和年龄)的文档.在foodsCollection中，包含带有食物名称"，成分"和图像"等字段的文档.现在，我想让用户按用户的意愿为食物添加书签.因此，我在名为Bookmark的用户文档中创建了另一个集合，并将 Food文档的ID 保存在Bookmark集合的文档中.现在，我想使用保存的食品文档ID获得唯一的带有书签的文档.我将写数据结构以进一步理解.
I'll start to explain my issue using an example, I have 2 root collections named Users and Foods. In Users collection, contains documents with User information such as Name, Image, and Age. In foodsCollection, contains documents with Fields such as Food_name, Ingredients, and Image. Now I want to let the users bookmark foods as user wish.Therefore I create one more collection in a user document named Bookmark and saved the Food document's Id in the Bookmark collection's documents. Now I want to get the only Bookmarked Document using saved food document Ids. I ll write my data structure for further understanding.
Foods(Collection) ----1ztEzZLkTp5XOZzsoYRL(Feilds--Name,Image,Ingradents,Document_Id)
----4Q6k0MifwEyoLs8rgZbs(Feilds--Name,Image,Ingradents,Document_Id)
----870BEaDFMkMWTi4VaXmh(Feilds--Name,Image,Ingradents,Document_Id)
[...]
Users(Collection)----User1(Document)----Bookmarks(Collection)----RandomId("Bookmarked_Doc_Id" - 1ztEzZLkTp5XOZzsoYRL)
----RandomId("Bookmarked_Doc_Id" - 870BEaDFMkMWTi4VaXmh)
----User2(Document)----Bookmarks(Collection)----RandomId("Bookmarked_Doc_Id" - 1ztEzZLkTp5XOZzsoYRL)
[...]
现在我想使用Bookmarked_Doc_Id获取Food Collection的文档数据
Now I want to get the Food collection's document data using Bookmarked_Doc_Id
例如，当User1单击书签"选项卡时，他可以看到2个具有名称，图像和渐变的书签.
For example, When User1 clicks bookmark tab, he can see 2 bookmarks with its name,image and ingradents.
如何归档?
rootRef.collection("Users").document(USER_ID).collection("Bookmarks").get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
@Override
public void onComplete(@NonNull Task<QuerySnapshot> task) {
if (task.isSuccessful()){
for (DocumentSnapshot document : task.getResult()){
if (document.exists()){
String getDocuments = document.get("Bookmark_Document_Id").toString();
loadBookmarks(getDocuments);
Log.d(TAG, "onComplete: "+" "+getDocuments);
}
}
}
}
});
private void loadBookmarks(String getDocuments) {
Query query = FirebaseFirestore.getInstance().collection("Foods").whereEqualTo("Document_Id",getDocuments);
PagedList.Config config = new PagedList.Config.Builder()
.setEnablePlaceholders(false)
.setPrefetchDistance(2)
.setInitialLoadSizeHint(2)
.setPageSize(3)
.build();
FirestorePagingOptions<FoodItems> options = new FirestorePagingOptions.Builder<FoodItems>()
.setQuery(query, config, FoodItems.class)
.build();
food_items_recycle_adapter = new Food_Items_Recycle_Adapter(options, progressIndicator,null);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
recyclerView.setAdapter(food_items_recycle_adapter);
food_items_recycle_adapter.notifyDataSetChanged();
food_items_recycle_adapter.startListening();
}
此代码仅向我显示最新添加的书签，而不显示所有书签.
This code only shows me the latest added bookmark instead of showing all bookmarks.
推荐答案
最后，我解决了我的问题，这就是我想要的:)
Finally, I solve my problem and this is what I wanted :)
enter code here final FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
if (user!=null){
String USER_ID = user.getUid();
rootRef.collection("Users").document(USER_ID).collection("Bookmarks")
.addSnapshotListener(new EventListener<QuerySnapshot>() {
@Override
public void onEvent(@Nullable QuerySnapshot value, @Nullable FirebaseFirestoreException error) {
if (error!=null){
Log.w(TAG, "Listen failed.", error);
return;
}
List<String> foodlist = new ArrayList<>();
assert value != null;
for (QueryDocumentSnapshot doc : value) {
if (doc.get("Bookmark_Document_Id") != null) {
foodlist.add(doc.getString("Bookmark_Document_Id"));
Log.d(TAG, "Food items are: " + foodlist);
Query query = rootRef.collection("Recipes").document("Food_Recipe").collection("Powder_Recipe").whereIn("Document_Id",foodlist);
PagedList.Config config = new PagedList.Config.Builder()
.setEnablePlaceholders(false)
.setPrefetchDistance(2)
.setInitialLoadSizeHint(2)
.setPageSize(3)
.build();
FirestorePagingOptions<FoodItems> options = new FirestorePagingOptions.Builder<FoodItems>()
.setQuery(query, config, FoodItems.class)
.build();
food_items_recycle_adapter = new Food_Items_Recycle_Adapter(options, progressIndicator,null);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
recyclerView.setAdapter(food_items_recycle_adapter);
food_items_recycle_adapter.notifyDataSetChanged();
food_items_recycle_adapter.startListening();
}else {
Log.d(TAG, "onEvent: this is nulll");
}
}
}
});
}
谢谢 @s_o_m_m_y_e_e ，您试图解决我的问题.应该有很多方法可以对此进行存档，但这可以按我的意愿进行工作.
Thank you @s_o_m_m_y_e_e, you tried to solve my issue. There are should be many ways to archive this, but this is working as I wanted.
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