如何计算父子中的子数

Question

database rules

my database

我在 firebase 数据库中写入数据时遇到问题它必须使用方法 postId() 为数据提供一个 ID 有时它会给我一个正确的 ID，而另一次它会给我一个错误的 ID 或创建了一个 ID 中的更新数据

所有用户的 id 必须如此 post

[用户 1]

postId1

postId2

postId3

postId4

postId5

.

postId100000

[用户 2]

postId1

postId2

postId3

postId4

postId5 .

.

postId100000

................................................ .........

        if (auth.getCurrentUser() != null) {


            mDatabase.child("AdUsersINFO").child(auth.getCurrentUser().getUid()).child(POSTID).setValue(adver,
                    new DatabaseReference.CompletionListener() {
                        @Override
                        public void onComplete(DatabaseError databaseError, DatabaseReference databaseReference) {
                            if (databaseError == null) {


                                Toast.makeText(getContext(), "Data is saved successfully", Toast.LENGTH_LONG).show();

                            } else {

                                Toast.makeText(getContext(), "Data isn,t saved , please try again", Toast.LENGTH_LONG).show();
                            }

                        }
                    });

            mAdUserDatabse = FirebaseDatabase.getInstance().getReference().child("AdUsersINFO").child(auth.getCurrentUser().getUid()).child(POSTID);
            mAdUserDatabse.addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {

                    mAdUserDatabse.child("userid").setValue(auth.getCurrentUser().getUid());
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });


        }

私有无效postId() {

    DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference().child("AdUsersINFO");
    rootRef.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {
            if (snapshot.hasChild(auth.getCurrentUser().getUid())) {
                // run some code

                mAdUserDatabse = FirebaseDatabase.getInstance().getReference().child("AdUsersINFO");
                mAdUserDatabse.addListenerForSingleValueEvent(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        for (DataSnapshot snap : dataSnapshot.getChildren()) {
                            Log.e(snap.getKey(), snap.getChildrenCount() + "");

                            if (snap.getChildrenCount() != 0) {

                                postId = "postId" + String.valueOf(snap.getChildrenCount() + 1);
                                SharedPreferencesUtils.setStringPreference(getActivity(), "postId", postId);

                            } else {
                                postId = "postId" + String.valueOf(1);
                                SharedPreferencesUtils.setStringPreference(getActivity(), "postId", postId);
                            }


                        }

                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {

                    }
                });
            } else {
                postId = "postId" + String.valueOf(1);
                SharedPreferencesUtils.setStringPreference(getActivity(), "postId", postId);
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

}

请救救我的命

Answer 1

你是运行一个循环并一次又一次地覆盖 postId 的值，因此 postId 等于最后一个 child 的计数。所以你总是得到最后一个用户的 postId 计数。

所以再看一遍

for (DataSnapshot snap : dataSnapshot.getChildren()) {
                        Log.e(snap.getKey(), snap.getChildrenCount() + "");

                        if (snap.getChildrenCount() != 0) {

                            postId = "postId" + String.valueOf(snap.getChildrenCount() + 1);
                            SharedPreferencesUtils.setStringPreference(getActivity(), "postId", postId);

                        } else {
                            postId = "postId" + String.valueOf(1);
                            SharedPreferencesUtils.setStringPreference(getActivity(), "postId", postId);
                        }


                    }

考虑为每个用户的 postId 使用单独的密钥，或者制作一个函数来为一个用户获取密钥，类似这样

public void getPostId(String userId) {
    final String postId = "post";
    DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference().child("AdUsersINFO").child(userId);
    rootRef.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {
            long c = snapshot.getChildrenCount();
            if(c==) postId = postId+"1";
            else postId = postId+ c+1;
        },

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
};

如何计算父子中的子数

how to get count of child inside the parent child

java

android

children

firebase-realtime-database