com.google.firebase.database.Query类的使用及代码示例

x33g5p2x  于2022-01-28 转载在 其他  
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本文整理了Java中com.google.firebase.database.Query类的一些代码示例，展示了Query类的具体用法。这些代码示例主要来源于Github/Stackoverflow/Maven等平台，是从一些精选项目中提取出来的代码，具有较强的参考意义，能在一定程度帮忙到你。Query类的具体详情如下：
包路径：com.google.firebase.database.Query
类名称：Query

Query介绍

[英]The Query class (and its subclass, DatabaseReference) are used for reading data. Listeners are attached, and they will be triggered when the corresponding data changes.

Instances of Query are obtained by calling startAt(), endAt(), or limit() on a DatabaseReference.
[中]查询类（及其子类DatabaseReference）用于读取数据。侦听器已附加，当相应的数据更改时，它们将被触发。
查询实例是通过调用数据库引用上的startAt（）、endAt（）或limit（）获得的。

代码示例

代码示例来源：origin: chat-sdk/chat-sdk-android

query = query.startAt(startTimestamp, Keys.Date);
query = query.orderByChild(Keys.Date).limitToLast(ChatSDK.config().messageHistoryDownloadLimit);
ChildEventListener listener = query.addChildEventListener(new FirebaseEventListener().onChildAdded((snapshot, s, hasValue) -> {
  if (hasValue) {

代码示例来源：origin: chat-sdk/chat-sdk-android

.endAt(endDate.getTime() - 1, Keys.Date)
    .limitToLast(numberOfMessages + 1);
query.addListenerForSingleValueEvent(new FirebaseEventListener().onValue((snapshot, hasValue) -> {
  if(hasValue) {
    List<Message> messages = new ArrayList<Message>();

代码示例来源：origin: chat-sdk/chat-sdk-android

private void removeListener () {
  if(cel != null) {
    ref.removeEventListener(cel);
  }
  if(vel != null) {
    ref.removeEventListener(vel);
  }
}

代码示例来源：origin: chat-sdk/chat-sdk-android

public Observable<Message> messageRemovedOn() {
    return Observable.create(e -> {

      Query query = FirebasePaths.threadMessagesRef(model.getEntityID());

      query = query.orderByChild(Keys.Date);
      query = query.limitToLast(ChatSDK.config().messageDeletionListenerLimit);

      ChildEventListener removedListener = query.addChildEventListener(new FirebaseEventListener().onChildRemoved((snapshot, hasValue) -> {
        if(hasValue) {
          MessageWrapper message = new MessageWrapper(snapshot);
          this.model.removeMessage(message.getModel());
//                    updateLastMessage().subscribe(new CrashReportingCompletableObserver());
          e.onNext(message.getModel());
        }
      }));
      FirebaseReferenceManager.shared().addRef(query, removedListener);
    });
  }

代码示例来源：origin: chat-sdk/chat-sdk-android

.startAt(value)
    .limitToFirst(limit);
query.keepSynced(true);
query.addListenerForSingleValueEvent(new FirebaseEventListener().onValue((snapshot, hasValue) -> {
  if (hasValue) {
    Object valueObject = snapshot.getValue();

代码示例来源：origin: FrangSierra/RxFirebase

@Override
  public void subscribe(final FlowableEmitter<DataSnapshot> emitter) throws Exception {
    final ValueEventListener valueEventListener = new ValueEventListener() {
      @Override
      public void onDataChange(DataSnapshot dataSnapshot) {
        emitter.onNext(dataSnapshot);
      }
      @Override
      public void onCancelled(final DatabaseError error) {
        if (!emitter.isCancelled())
          emitter.onError(new RxFirebaseDataException(error));
      }
    };
    emitter.setCancellable(new Cancellable() {
      @Override
      public void cancel() throws Exception {
        query.removeEventListener(valueEventListener);
      }
    });
    query.addValueEventListener(valueEventListener);
  }
}, strategy);

代码示例来源：origin: FrangSierra/RxFirebase

query.addChildEventListener(childEventListener);

代码示例来源：origin: Stoick001/SnapchatClone

private void listenForData() {
  DatabaseReference usersDB = FirebaseDatabase.getInstance().getReference().child("users");
  Query query = usersDB.orderByChild("username").startAt(mInput.getText().toString()).endAt(mInput.getText().toString() + "\uf8ff");
  query.addChildEventListener(new ChildEventListener() {
    @Override
    public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {

代码示例来源：origin: firebase/firebase-admin-java

/**
 * Create a query constrained to only return the child node with the given key and value. Note
 * that there is at most one such child as keys are unique.
 *
 * @param value The value to query for
 * @param key The name of the child
 * @return A query with the new constraint
 */
public Query equalTo(boolean value, String key) {
 validateEqualToCall();
 return this.startAt(value, key).endAt(value, key);
}

代码示例来源：origin: thinkmobiles/Android-MVP-vs-MVVM-Samples

public final void getCheckInByEmail(final String _email, final OnLoadCallback<CheckIn> loadCallback) {
  mDatabaseCheckIn.orderByChild("email").equalTo(_email).addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
      long count = dataSnapshot.getChildrenCount();
      Log.d(TAG, TABLE_CHECK_IN + " | MyCheckIns | Count is: " + count);
      final List<CheckIn> checkIns = new ArrayList<CheckIn>();
      for (final DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
        final CheckIn checkIn = dataSnapshot1.getValue(CheckIn.class);
        checkIns.add(checkIn);
        Log.d(TAG, TABLE_CHECK_IN + " | MyCheckIns | Value " + checkIn.checkInMessage);
      }
      loadCallback.onDataChange(checkIns);
    }
    @Override
    public void onCancelled(DatabaseError databaseError) {
      Log.d(TAG, TABLE_CHECK_IN + " | MyCheckIns | Failed to read: ", databaseError.toException());
      loadCallback.onCancelled();
    }
  });
}

代码示例来源：origin: akshayejh/Lapit---Android-Firebase-Chat-App

Query messageQuery = messageRef.orderByKey().endAt(mLastKey).limitToLast(10);
messageQuery.addChildEventListener(new ChildEventListener() {
  @Override
  public void onChildAdded(DataSnapshot dataSnapshot, String s) {

代码示例来源：origin: UdacityAndroidDevScholarship/quiz-app

@Override
public void fetchResources(int startFrom, int limit, Callback<List<Resource>> callback) {
  ValueEventListener listener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot snapshot) {
      if (snapshot != null) {
        List<Resource> resources = new ArrayList<>();
        for (DataSnapshot childSnapshot : snapshot.getChildren()) {
          Resource resource = childSnapshot.getValue(Resource.class);
          resources.add(resource);
        }
        callback.onReponse(resources);
      }
    }
    @Override
    public void onCancelled(DatabaseError databaseError) {
      callback.onError();
    }
  };
  Query resourcesQuery = mResourcesRef.orderByChild(KEY_TIMESTAMP);
  if (limit > 0) {
    resourcesQuery.limitToFirst(limit);
  }
  resourcesQuery.addValueEventListener(listener);
  mValueListeners.add(listener);
}

代码示例来源：origin: firebase/firebase-admin-java

/**
 * Create a query constrained to only return child nodes with a value less than or equal to the
 * given value, using the given orderBy directive or priority as default.
 *
 * @param value The value to end at, inclusive
 * @return A Query with the new constraint
 * @since 2.0
 */
public Query endAt(boolean value) {
 return endAt(value, null);
}

代码示例来源：origin: TomGrill/gdx-firebase

@Override
public void addListenerForSingleValueEvent(final ValueEventListener listener) {
  query.addListenerForSingleValueEvent(new com.google.firebase.database.ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
      listener.onDataChange(new DesktopDataSnapshot(dataSnapshot));
    }
    @Override
    public void onCancelled(DatabaseError databaseError) {
      listener.onCancelled(new DesktopDatabaseError(databaseError));
    }
  });
}

代码示例来源：origin: firebase/snippets-android

private void queryRecentScores() {
  scoresRef.orderByValue().limitToLast(4).addChildEventListener(new ChildEventListener() {
    @Override
    public void onChildAdded(@NonNull DataSnapshot snapshot, String previousChild) {
  scoresRef.orderByValue().limitToLast(2).addChildEventListener(new ChildEventListener() {
    @Override
    public void onChildAdded(@NonNull DataSnapshot snapshot, String previousChild) {

代码示例来源：origin: hieuapp/android-firebase-chat

mapQuery.get(id).addChildEventListener(mapChildListener.get(id));
  mapMark.put(id, true);
} else {
  mapQuery.get(id).removeEventListener(mapChildListener.get(id));
  mapQuery.get(id).addChildEventListener(mapChildListener.get(id));
  mapMark.put(id, true);

代码示例来源：origin: firebase/firebase-admin-java

/**
 * Create a query constrained to only return child nodes with a value greater than or equal to the
 * given value, using the given orderBy directive or priority as default.
 *
 * @param value The value to start at, inclusive
 * @return A Query with the new constraint
 */
public Query startAt(String value) {
 return startAt(value, null);
}

代码示例来源：origin: firebase/quickstart-java

public void doRun() throws JobInterruptException {
  DatabaseReference ref = FirebaseDatabase.getInstance().getReference();
  // Top 5 Posts in the database, ordered by stars
  // [START top_posts_query]
  Query topPostsQuery = ref.child("posts").orderByChild("starCount").limitToLast(5);
  // [END top_posts_query]
  // All Users
  final DatabaseReference allUsersRef = ref.child("users");
  topPostsQuery.addListenerForSingleValueEvent(new ValueEventListener() {
    public void onDataChange(final DataSnapshot topPostsSnapshot) {
      allUsersRef.addListenerForSingleValueEvent(new ValueEventListener() {
        public void onDataChange(DataSnapshot allUsersSnapshot) {
          // Get users and posts as lists
          Map<String,User> users = allUsersSnapshot.getValue(new GenericTypeIndicator<Map<String, User>>() {});
          List<Post> posts = topPostsSnapshot.getValue(new GenericTypeIndicator<List<Post>>() {});
          // Send email to all users about the top 5 posts
          MyEmailer.sendWeeklyEmail(users, posts);
        }
        public void onCancelled(DatabaseError databaseError) {
          System.out.println("WeeklyEmailJob: could not get all users");
          System.out.println("WeeklyEmailJob: " + databaseError.getMessage());
        }
      });
    }
    public void onCancelled(DatabaseError databaseError) {
      System.out.println("WeeklyEmailJob: could not get top posts");
      System.out.println("WeeklyEmailJob: " + databaseError.getMessage());
    }
  });
}

代码示例来源：origin: dragosholban/AndroidMyInstagramApp

Query likesQuery = database.child("likes").orderByChild("imageId").equalTo(image.key);
likesQuery.addChildEventListener(new ChildEventListener() {
  @Override
  public void onChildAdded(DataSnapshot dataSnapshot, String s) {

代码示例来源：origin: dragosholban/AndroidMyInstagramApp

Query imagesQuery = database.child("images").orderByKey().limitToFirst(100);
imagesQuery.addChildEventListener(new ChildEventListener() {
  @Override
  public void onChildAdded(DataSnapshot dataSnapshot, String s) {

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