java - 如何查询具有不同 Firebase 数据库名称的数据？

Question

这是我作为示例给出的 Firebase 数据库示例。这里我想做“[phone]”值的电话号码和文本的值一起用recycler视图查询和排序值。我只是设法做到了。但不是我想要的方式。此电话号码将有两个或多个值。您可以在数据库中看到这一点。

“[phone]”：“A”和“[phone]”：“AA”。当我质疑这个数字时，我想看到这个数据。但是我无法创建 CategoryItem 类，因为我的数据库名称是可变的。我不知道该怎么做。不会有固定的数据库名称。用户会查询不同的号码。如何为此创建 CategoryItem 类？

我的 Firebase 数据库

{
  "ContactPhoneNumbers" : {
    "-LcaHYcsoGA-VT8yvgGf" : {
      "[phone]" : "A",
      "[phone]" : "B",
      "[phone]" : "C",
      "[phone]" : "D",
      "[phone]" : "E",
      "[phone]" : "F",
      "[phone]" : "G",
      "[phone]" : "H",
      "[phone]" : "I",
      "[phone]" : "J",
      "[phone]" : "K",
      "[phone]" : "L",
      "05056960007" : "M"
    },
    "-LcaH_gtgarJwbY5-C08" : {
      "[phone]" : "AA",
      "[phone]" : "BB",
      "[phone]" : "CAC",
      "[phone]" : "AAA",
      "[phone]" : "CAB",
      "[phone]" : "BB",
      "[phone]" : "A",
      "[phone]" : "BBB",
      "[phone]" : "DDD",
      "[phone]" : "EEE",
      "[phone]" : "FFF",
      "[phone]" : "L",
      "05056960007" : "M"
    }
  }
}

我的活动

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);
    }
}

我的分类项目

这段代码完全是一个例子。当我将名称“字符串”写为字符串时，我需要在电话号码中创建一个名称。我不想要这个。我想查看对应电话号码的值。

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;
    }

}

标签： javaandroidfirebasefirebase-realtime-database

Answer 1

因为您使用的是动态键，所以没有有效的方法来orderByChild()获得您想要的结果，而无需将整个“ContactPhoneNumbers”节点下载到客户端设备然后执行排序和过滤。另一种方法是保留联系人的索引。

orderByChild()

这仅对小型数据集有用。当“ContactPhoneNumbers”变大时，不要依赖它，因为它会增加您的成本。每次调用时，您的联系人数据库都会被完整下载。

String phoneSearchText = "[phone]";
Query q = mUserDatabase.orderByChild(phoneSearchText).startAt("");

索引

当您的数据依赖于动态键时，您已经实现了自定义索引实现，而不是使用 RTDB 的内置索引系统（请参阅索引数据）。

您可以在客户端（更便宜）或服务器端（更易于维护）构建和维护索引。

为了安全和可维护性，我将包含一些修改后的代码，用于基于Cloud Functions for Firebase构建的服务器端实现。

此代码将生成以下索引，可以查询电话号码并包含所有不同的变体。对“ContactPhoneNumbers”树所做的任何更改都将自动镜像到该索引。您应该保护此索引不被客户端设备更改。

{
  "ContactPhoneNumbersIndex": {
    "[phone]": {
      "-LcaHYcsoGA-VT8yvgGf": "A",
      "-LcaH_gtgarJwbY5-C08": "AA"
    },
    "[phone]": {
      "-LcaHYcsoGA-VT8yvgGf": "B",
      "-LcaH_gtgarJwbY5-C08": "BB"
    },
    "[phone]": {
      "-LcaHYcsoGA-VT8yvgGf": "C",
      "-LcaH_gtgarJwbY5-C08": "CAC"
    },
    "[phone]": {
      "-LcaHYcsoGA-VT8yvgGf": "D",
      "-LcaH_gtgarJwbY5-C08": "AAA"
    },
    "[phone]": {
      "-LcaHYcsoGA-VT8yvgGf": "E",
      "-LcaH_gtgarJwbY5-C08": "CAB"
    },
    "[phone]": {
      "-LcaHYcsoGA-VT8yvgGf": "F",
      "-LcaH_gtgarJwbY5-C08": "BB"
    },
    "[phone]": {
      "-LcaHYcsoGA-VT8yvgGf": "G",
      "-LcaH_gtgarJwbY5-C08": "A"
    },
    "[phone]": {
      "-LcaHYcsoGA-VT8yvgGf": "H",
      "-LcaH_gtgarJwbY5-C08": "BBB"
    },
    "[phone]": {
      "-LcaHYcsoGA-VT8yvgGf": "I",
      "-LcaH_gtgarJwbY5-C08": "DDD"
    },
    "[phone]": {
      "-LcaHYcsoGA-VT8yvgGf": "J",
      "-LcaH_gtgarJwbY5-C08": "EEE"
    },
    "[phone]": {
      "-LcaHYcsoGA-VT8yvgGf": "K",
      "-LcaH_gtgarJwbY5-C08": "FFF"
    },
    "[phone]": {
      "-LcaHYcsoGA-VT8yvgGf": "L",
      "-LcaH_gtgarJwbY5-C08": "L"
    },
    "05056960007": {
      "-LcaHYcsoGA-VT8yvgGf": "M",
      "-LcaH_gtgarJwbY5-C08": "M"
    }
  }
}

由于您在数据库结构中使用推送 ID，下面编写的函数在包含推送 ID 的级别上运行，对整个组而不是单个条目执行操作。您可以在此处阅读函数文档并观看有关该主题的一些Firecast。

// 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);
    });

课程

对于您的数据库结构，创建一个类是一项艰巨的任务。一种方法是上一步查看节点树并查看分组中的联系人，您可以在其中围绕值的内部映射或联系人对象列表包装一个类。

我在下面给出的示例维护内部地图并与之交互。

SetValue不幸的是，Firebase SDK 没有公开类似于自定义比较函数的“序列化”方法，因此您将无法GetValue直接使用此类。

上传到数据库：

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

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

从数据库下载：

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

这堂课不完整。有足够的汁液流动，但还有很大的改进空间。

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);
  }
}