java - 如何通过在 Firebase 中搜索特定节点来添加现有文档中的数据？ (安卓)

Question

有一份文件是学生文件，其中包含类(class)、用户名、状态等学生数据。我想通过搜索 emailid 在现有文档中添加另一个名为 uid 的节点

例如，在包含 emailid 的文档中:“abc@gmail.com”，我想在包含 emailid 的文档中添加 uid:“111032”。

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
        final DatabaseReference studentRef = rootRef.child("STUDENT");

        lg.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                username = un.getText().toString().trim();
                String password= pw.getText().toString().trim();
                lg.setText("Logging in...");
                firebaseAuth.signInWithEmailAndPassword(username, password)
                        .addOnCompleteListener(Welcome.this, new OnCompleteListener<AuthResult>() {
                            @Override
                            public void onComplete(@NonNull Task<AuthResult> task) {
                                if (task.isSuccessful()) {
                                    firebaseAuth = FirebaseAuth.getInstance();
                                    final String current_user_id = firebaseAuth.getCurrentUser().getUid();
                                    //Save UID to database
                                    Query emailAddressQuery = studentRef.orderByChild("emailid").equalTo(username).limitToFirst(1);
                                    ValueEventListener valueEventListener = new ValueEventListener() {
                                        @Override
                                        public void onDataChange(DataSnapshot dataSnapshot) {
                                            for(DataSnapshot ds : dataSnapshot.getChildren()) {
                                                Map<String, Object> uidUpdate = new HashMap<String, Object>();
                                                uidUpdate.put("uid", current_user_id);
                                                ds.getRef().updateChildren(uidUpdate);
                                            }
                                        }

                                        @Override
                                        public void onCancelled(@NonNull DatabaseError databaseError) {
                                            Log.d("TAG", databaseError.getMessage()); //Don't ignore errors!

                                        }
                                    };
                                    emailAddressQuery.addListenerForSingleValueEvent(valueEventListener);
                                    Intent i=new Intent(Welcome.this,Home.class);
                                   // i.putExtra("useremail", username);
                                    startActivity(i);
                                    lg.setText("Log In");
                                } else {
                                    Toast.makeText(getApplicationContext(), "Log In Failed", Toast.LENGTH_SHORT).show();
                                    lg.setText("Log in");
                                }

                                // ...
                            }
                        });
            }
        });

上面的代码实际上是在登录按钮中，用户登录时获取 uid 并将其保存到特定个人资料的信息中。 this is the image with more detailed information .

As shown in this image ，我想通过 emailid 进行搜索(以黄色显示)并在该特定文档中添加名为 uid 的节点。

旧代码:

username = un.getText().toString().trim();
firebaseAuth = FirebaseAuth.getInstance();
String current_user_id = firebaseAuth.getCurrentUser().getUid();
ref= FirebaseDatabase.getInstance().getReference().child("STUDENT").child(username);
                                    Map<String, Object> updates = new HashMap<String, Object>();
                                    updates.put("uid", current_user_id);
                                    ref.updateChildren(updates);

这段代码可以工作，但是我们必须传递文档的名称，而我想通过文档中的子节点传递数据。

Answer 1

要解决此问题，请使用以下代码行:

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference studentRef = rootRef.child("STUDENT");
Query emailAddressQuery = studentRef.orderByChild("emailid").equalTo("abc@gmail.com").limitToFirst(1);
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            Map<String, Object> uidUpdate = new HashMap<String, Object>();
            uidUpdate.put("uid", uid);
            ds.getRef().updateChildren(uidUpdate).addOnCompleteListener(new OnCompleteListener<Void>() {
                @Override
                public void onComplete(@NonNull Task<Void> task) {
                    if (task.isSuccessful()) {
                        Log.d("TAG", "task is successful!");
                    } else {
                        Log.d("TAG", task.getException().getMessage());
                    }
                }
            });
        }
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Log.d("TAG", databaseError.getMessage()); //Don't ignore errors!
    }
};
emailAddressQuery.addListenerForSingleValueEvent(valueEventListener);

此操作的结果将是用户对象中uid的更新。