用户关闭应用程序时从Firebase实时数据库中删除数据

Question

我对Android dev和Firebase很陌生。

我需要以下帮助：

 @Override
public void onDestroyView() {
    super.onDestroyView();


    mAuth.signOut();

    mDatabase.child("users").child(user.getUid()).removeValue();
    Log.i("User: ", "Not saved in database");

    user.delete()
            .addOnCompleteListener(new OnCompleteListener<Void>() {
                @Override
                public void onComplete(@NonNull Task<Void> task) {
                    if (task.isSuccessful()) {
                        Log.d(TAG, "User account deleted.");

                    }


                }



            });

}

提前谢谢你。

公共类AddUsername扩展片段实现View.OnClickListener,TextWatcher{

public AddUsername() {

}


public interface FragmentComm {
    void toSetName();
}

private TextView title, headings, handleError;
private EditText addUsername;
private Button nextButton;
private String getUsername;
private FirebaseAuth mAuth;
private FirebaseUser user;
private DatabaseReference mDatabase;
private FragmentComm fragmentComm;

@Override
public void onAttach(Context context) {
    super.onAttach(context);

    fragmentComm = (FragmentComm) getActivity();
    user = FirebaseAuth.getInstance().getCurrentUser();
    mAuth = FirebaseAuth.getInstance();
    mDatabase = FirebaseDatabase.getInstance().getReference();

}

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.add_username, container, false);

    title = view.findViewById(R.id.username_title);
    headings = view.findViewById(R.id.display_user_message);
    handleError = view.findViewById(R.id.message_error);
    addUsername = view.findViewById(R.id.addUsername);
    nextButton = view.findViewById(R.id.nextButton);
    nextButton.setOnClickListener(this);
    addUsername.addTextChangedListener(this);


    return view;
}


@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {

}

@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {

}


@Override
public void afterTextChanged(Editable s) {


    getUsername = addUsername.getText().toString();

    if (getUsername.isEmpty()) {

        handleError.setVisibility(View.GONE);
        nextButton.setBackgroundColor(Color.parseColor("#EEEEEE"));
        nextButton.setTextColor(Color.parseColor("#BDBDBD"));
        nextButton.setEnabled(false);


    } else {

        Query query = FirebaseDatabase.getInstance().getReference().child("users").orderByChild("username").equalTo(getUsername);
        query.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                if (dataSnapshot.exists()) {

                    handleError.setText(R.string.username_not_available);
                    handleError.setVisibility(View.VISIBLE);
                    handleError.setTextColor(Color.parseColor("#F50057"));
                    nextButton.setBackgroundColor(Color.parseColor("#EEEEEE"));
                    nextButton.setTextColor(Color.parseColor("#BDBDBD"));
                    nextButton.setEnabled(false);

                } else {

                    handleError.setText(R.string.username_available);
                    handleError.setVisibility(View.VISIBLE);
                    handleError.setTextColor(Color.parseColor("#26C485"));
                    nextButton.setBackgroundColor(Color.parseColor("#0277BD"));
                    nextButton.setTextColor(Color.parseColor("#FFFFFF"));
                    nextButton.setEnabled(true);

                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                Log.i("Give info", "Error");


            }
        });

    }

}


@Override
public void onClick(View v) {

    switch (v.getId()) {

        case R.id.nextButton:

            checkUsernameAlreadyExist();

    }


}

private void checkUsernameAlreadyExist() {

    getUsername = addUsername.getText().toString();


    Query query = FirebaseDatabase.getInstance().getReference().child("users").orderByChild("username").equalTo(getUsername);
    query.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            if (dataSnapshot.exists()) {

                handleError.setText(R.string.username_not_available);
                handleError.setVisibility(View.VISIBLE);
                handleError.setTextColor(Color.parseColor("#F50057"));


            } else {

                handleError.setText(R.string.username_available);
                handleError.setVisibility(View.VISIBLE);
                handleError.setTextColor(Color.parseColor("#26C485"));

               fragmentComm.toSetName();
                setDatabaseName();

            }
        }


        @Override
        public void onCancelled(DatabaseError databaseError) {
            Log.i("Give info", "Error");


        }
    });

}


private void setDatabaseName() {

    mDatabase.child("users").child(user.getUid()).child("username").setValue(getUsername);


}

Answer 1

我认为这可能是ondisconnect处理程序的一个很好的用例。这些是应用程序在连接Firebase数据库时发送给它的写指令，数据库服务器在检测到客户端消失后执行这些指令。

这方面的一个例子是：

private void setDatabaseName() {
  DatabaseReference usernameRef = mDatabase.child("users").child(user.getUid()).child("username");
  usernameRef.setValue(getUsername);
  usernameRef.onDisconnection().removeValue();
}

有关这方面的更多信息，请参阅关于ondisconnect处理程序的Firebase文档。

• Firebase android：使用户名唯一
• 检查子级#askfirebase唯一值的Firebase安全规则
• 如何防止FireBase中重复用户属性？