如何使用不同的 Firebase 数据库名称查询数据？

Question

Here's an example of a Firebase database that I've given as an example. Here I want to do the "+90 505 696 1234" value phone number with the value of the text to query and sort the value with the recycler view. I only managed to do that. But not in the way I want. This phone number will have two or more values. You can see this in the database.

"+90 505 696 1234": "A" and "+90 505 696 1234": "AA". I want to see this data when I question this number. But I can't create the CategoryItem class because my database name will be variable. I don't know how to do it. There will not be a fixed database name. Users will query different numbers. How do I create a CategoryItem class for this? I would be glad if you help. Sorry for my bad English.

My Firebase Database

{
  "ContactPhoneNumbers" : {
    "-LcaHYcsoGA-VT8yvgGf" : {
      "+90 505 696 1234" : "A",
      "+90 506 854 2345" : "B",
      "+90 530 408 3456" : "C",
      "+90 535 966 4567" : "D",
      "+90 536 782 5678" : "E",
      "+90 546 934 67 89" : "F",
      "+905304080001" : "G",
      "+905316910002" : "H",
      "+905359660003" : "I",
      "+905367820004" : "J",
      "+905425420005" : "K",
      "+905469340006" : "L",
      "05056960007" : "M"
    },
    "-LcaH_gtgarJwbY5-C08" : {
      "+90 505 696 1234" : "AA",
      "+90 506 854 2345" : "BB",
      "+90 530 408 3456" : "CAC",
      "+90 535 966 4567" : "AAA",
      "+90 536 782 5678" : "CAB",
      "+90 546 934 67 89" : "BB",
      "+905304080001" : "A",
      "+905316910002" : "BBB",
      "+905359660003" : "DDD",
      "+905367820004" : "EEE",
      "+905425420005" : "FFF",
      "+905469340006" : "L",
      "05056960007" : "M"
    }
  }
}

My Activity

public class MainActivity extends AppCompatActivity {

    EditText Search_Edit_Text;
    Button Search_Button;
    RecyclerView Search_Contact_List;

    DatabaseReference mUserDatabase;

    FirebaseRecyclerOptions<CategoryItem> options,options2;
    FirebaseRecyclerAdapter<CategoryItem,CategoryViewHolder> adapter;

    Query firebaseSearchQuery,asd;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        mUserDatabase = FirebaseDatabase.getInstance().getReference().child("ContactPhoneNumbers");


        Search_Edit_Text = (EditText) findViewById(R.id.Search_Edit_Text);
        Search_Button = (Button) findViewById(R.id.Search_Button);

        Search_Contact_List = (RecyclerView) findViewById(R.id.Search_Contact_List);
        Search_Contact_List.setHasFixedSize(true);
        GridLayoutManager gridLayoutManager = new GridLayoutManager(getBaseContext(),2);
        Search_Contact_List.setLayoutManager(gridLayoutManager);




        Search_Button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                String searchText = Search_Edit_Text.getText().toString().trim();

                firebaseUserSearch(searchText);
            }
        });

 }

    private void firebaseUserSearch(final String searchText) {


        firebaseSearchQuery = mUserDatabase.orderByChild(searchText).startAt("").endAt("" + "\uf8ff");

        options2 = new FirebaseRecyclerOptions.Builder<CategoryItem>()
                .setQuery(firebaseSearchQuery,CategoryItem.class)
                .build();

        adapter = new FirebaseRecyclerAdapter<CategoryItem, CategoryViewHolder>(options2) {
            @Override
            protected void onBindViewHolder(@NonNull final CategoryViewHolder holder, int position, @NonNull final CategoryItem model) {

                Toast.makeText(MainActivity.this, model.getName(), Toast.LENGTH_SHORT).show();
            }


            @NonNull
            @Override
            public CategoryViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {

                View itemView = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.list_layout,parent,false);
                return new CategoryViewHolder(itemView);

            }
        };

        setCategory();
    }

    private void setCategory() {

        adapter.startListening();
        Search_Contact_List.setAdapter(adapter);
    }
}

My CategoryItem

This code is completely an example. When I write the name "string" as string, I need to create a name in the phone numbers. Idont want this. I want to see the value of the corresponding phone number.

public class CategoryItem {

    public String name ;

    public CategoryItem() {

    }

    public CategoryItem(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

Answer 1

You can't do that. it's impossible to get a specific key without knowing it's name. Are you using keys to index the data? if so maybe don't do that and just store a index in the node so you can set a final title.

Answer 2

I've played around with this a bit. Because you are using dynamic keys, there is no efficient way to use orderByChild() to get the result you desire without having to download the entire "ContactPhoneNumbers" node to the client device and then performing the sort and filter. The alternative is to keep an index of the contacts.

orderByChild()

This is only useful for small datasets. Do not rely on it for when "ContactPhoneNumbers" gets larger as it will drive up your costs. Each time this is called, your contacts database will be downloaded in it's entirety.

String phoneSearchText = "+90 530 408 3456";
Query q = mUserDatabase.orderByChild(phoneSearchText).startAt("");

Indexing

When your data relies on dynamic keys, you have implement a custom index implementation rather than use the RTDB's built-in indexing system (see indexing data ).

You can build and maintain the index either on the client (cheaper) or server side (easier to maintain).

For the sake of security and maintainability, I'll include some modified code for a server-side implementation built on Cloud Functions for Firebase .

This code will generate the following index which can be queried for a phone number and contain all the different variants. Any changes made to the "ContactPhoneNumbers" tree will be mirrored to this index automatically. You should secure this index from being changeable by client devices.

{
  "ContactPhoneNumbersIndex": {
    "+90 505 696 1234": {
      "-LcaHYcsoGA-VT8yvgGf": "A",
      "-LcaH_gtgarJwbY5-C08": "AA"
    },
    "+90 506 854 2345": {
      "-LcaHYcsoGA-VT8yvgGf": "B",
      "-LcaH_gtgarJwbY5-C08": "BB"
    },
    "+90 530 408 3456": {
      "-LcaHYcsoGA-VT8yvgGf": "C",
      "-LcaH_gtgarJwbY5-C08": "CAC"
    },
    "+90 535 966 4567": {
      "-LcaHYcsoGA-VT8yvgGf": "D",
      "-LcaH_gtgarJwbY5-C08": "AAA"
    },
    "+90 536 782 5678": {
      "-LcaHYcsoGA-VT8yvgGf": "E",
      "-LcaH_gtgarJwbY5-C08": "CAB"
    },
    "+90 546 934 67 89": {
      "-LcaHYcsoGA-VT8yvgGf": "F",
      "-LcaH_gtgarJwbY5-C08": "BB"
    },
    "+905304080001": {
      "-LcaHYcsoGA-VT8yvgGf": "G",
      "-LcaH_gtgarJwbY5-C08": "A"
    },
    "+905316910002": {
      "-LcaHYcsoGA-VT8yvgGf": "H",
      "-LcaH_gtgarJwbY5-C08": "BBB"
    },
    "+905359660003": {
      "-LcaHYcsoGA-VT8yvgGf": "I",
      "-LcaH_gtgarJwbY5-C08": "DDD"
    },
    "+905367820004": {
      "-LcaHYcsoGA-VT8yvgGf": "J",
      "-LcaH_gtgarJwbY5-C08": "EEE"
    },
    "+905425420005": {
      "-LcaHYcsoGA-VT8yvgGf": "K",
      "-LcaH_gtgarJwbY5-C08": "FFF"
    },
    "+905469340006": {
      "-LcaHYcsoGA-VT8yvgGf": "L",
      "-LcaH_gtgarJwbY5-C08": "L"
    },
    "05056960007": {
      "-LcaHYcsoGA-VT8yvgGf": "M",
      "-LcaH_gtgarJwbY5-C08": "M"
    }
  }
}

Because of your use of push IDs in your database structure, the functions written below operate at the level containing the push IDs, performing operations on whole groups rather than individual entries. You can read the documentation for functions here and watch some Firecasts on the subject.

// Import and initialize Cloud Functions and Admin SDKs
const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

const ADMIN_DB_REF_PHONE_NUMBER_INDEX = admin.database().ref('/ContactPhoneNumbersIndex');

// Add entirely new contact groups to index
exports.contactGroups_created = functions.database.ref('/ContactPhoneNumbers/{groupPushId}')
    .onCreate((snapshot, context) => {
      const groupId = context.params.groupPushId;

      // prepare atomic write
      const pendingUpdates = {};

      const contactsMap = snapshot.val();

      for (const phone in contactsMap) {
        if (contactsMap.hasOwnProperty(phone)) {
          let name = contactsMap[phone];

          // add data to update
          pendingUpdates[`${phone}/${groupId}`] = name;
        }
      }

      // commit the update to the index
      return ADMIN_DB_REF_PHONE_NUMBER_INDEX.update(pendingUpdates);
    });

// Remove deleted contact groups from index
exports.contactGroups_deleted = functions.database.ref('/ContactPhoneNumbers/{groupPushId}')
    .onDelete((snapshot, context) => {
      const groupId = context.params.groupPushId;

      // prepare atomic write
      const pendingUpdates = {};

      const contactsMap = snapshot.val();

      for (const phone in contactsMap) {
        if (contactsMap.hasOwnProperty(phone)) {
          let name = contactsMap[phone];

          // add data to update
          pendingUpdates[`${phone}/${groupId}`] = null; // null will delete data at given location
        }
      }

      // commit the update to the index
      return ADMIN_DB_REF_PHONE_NUMBER_INDEX.update(pendingUpdates);
    });

// Handle contact changes
exports.contactGroups_changed = functions.database.ref('/ContactPhoneNumbers/{groupPushId}')
    .onUpdate((change, context) => {
      const groupId = context.params.groupPushId;

      // prepare atomic write
      const pendingUpdates = {};

      // prepare changes map
      const changeMap = {};

      // add before state to changeMap
      const beforeContactsMap = change.before.val();
      for (const phone in beforeContactsMap) {
        if (beforeContactsMap.hasOwnProperty(phone)) {
          let name = beforeContactsMap[phone];
          changeMap[phone] = { before: name };
        }
      }

      // add after state to changeMap
      const afterContactsMap = change.after.val();
      for (const phone in afterContactsMap) {
        if (afterContactsMap.hasOwnProperty(phone)) {
          let name = afterContactsMap[phone];

          if (changeMap[phone]) {
            changeMap[phone].after = name;
          } else {
            changeMap[phone] = { after: name };
          }
        }
      }

      // look for changes and commit any differences
      for (const phone in changeMap) {
        if (changeMap.hasOwnProperty(phone)) {
          let nameChange = changeMap[phone];

          if (nameChange.before != nameChange.after) {
            // changed
            pendingUpdates[`${phone}/${groupId}`] = nameChange.after || null; // use updated value or fallback to null to delete
          }
        }
      }

      // commit the update to the index
      return ADMIN_DB_REF_PHONE_NUMBER_INDEX.update(pendingUpdates);
    });

Classes

With your database structure, creating a class is a difficult task. One method is to take a step up the node tree and look at the contacts in groups, where you can wrap a class around an internal map of your values or a list of Contact objects.

The example I've given below maintains and interacts with an internal map.

Unfortunately the Firebase SDK doesn't expose a "serialize" method akin to custom compare functions so you will not be able to use this class with SetValue and GetValue directly.

To upload to the database:

ContactGroup mContacts = ...
DatabaseReference groupRef = mContactGroupsReference.push();

mContacts.setId(groupRef.getKey()); // optional
groupRef.SetValue(mContacts.toMap());

To download from the database:

@Override
public void onDataChange(DataSnapshot dataSnapshot) {
  ContactGroup contacts = new ContactGroup(dataSnapshot);
  // or
  ContactGroup contacts = new ContactGroup(dataSnapshot.getKey(), dataSnapshot.getValue());
}

This class is incomplete. There's enough to get the juices flowing but there is plenty of room for improvement.

public class ContactGroup {
  private id = null;
  private Map<String, String> contactMap = new HashMap<>(); // Phone => Name

  public ContactGroup() {
  }

  public ContactGroup(String id, Map<String, Object> contacts) {
    this.id = id;
    if (contacts == null)
      return;
    for (Map.Entry<String, Object> entry : contacts.entrySet()) {
      contactMap.put(entry.getKey(), entry.getValue().toString());
    }
  }

  public ContactGroup(DataSnapshot snapshot) {
    this(snapshot.getKey(), snapshot.getValue());
    // do something else with snapshot? save the ref?
  }

  public void add(String name, String phone) {
    contactMap.put(phone, name);
  }

  public String getNameForPhone(String phone) {
    return contactMap.get(phone);
  }

  public String getPhoneForName(String name) {
    for (Map.Entry<String, String> entry : contactMap.entrySet()) {
      if (entry.getValue() == name)
        return entry.getKey();
    }
    return null;
  }

  public getId() {
    return id;
  }

  public setId() {
    return id;
  }

  @Exclude
  public static ContactGroup fromMap(Map<String, Object> valueMap) {
    return new ContactGroup(null, valueMap);
  }

  @Exclude
  public Map<String, Object> toMap() {
    return new HashMap<String, Object>(contactMap);
  }
}

There's a lot to unpack here (Which is why your question got downvoted, be more specific in the future). Good luck!