Can't save a message in firebase database

Question

I am trying to save a message object in the firebase database, when I run the code I get no errors, everything looks to be fine but when I go to firebase website, nothing appears in the database

public class MainChatActivity extends AppCompatActivity {
    private DatabaseReference mDatabaseReference;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_chat);

        mDatabaseReference = FirebaseDatabase.getInstance().getReference();

        mSendButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                sendMessage();
            }
        });
    }

    private void sendMessage() {
        String input = mInputText.getText().toString();
        if(!input.equals("")){
            InstantMessage chat=new InstantMessage(input, mDisplayName);
            mDatabaseReference.child("children").push().setValue(chat);
            mInputText.setText("");
        }
    }
}

public class InstantMessage {
    private String message;
    private String author;

    public InstantMessage(String message, String author) {
        this.message = message;
        this.author = author;
    }

    public InstantMessage() {
    }

    public String getMessage() {
        return message;
    }

    public String getAuthor() {
        return author;
    }
}

I expect to save the message with author name in a directory named "messages" in firebase, but that's not happening

Answer 1

Change your firebase database rules to the following:

{
  "rules": {
    ".read": true
    ".write": true
  }
}

It allows read/write access to all users under any conditions.

Warning: NEVER use this ruleset in production; it allows anyone to overwrite your entire database.

Answer 2

It seems its permission issue

Make sure you are permission for READ/WRITE on the database, check the rules and make them public

{
  "rules": {
    ".read": true
    ".write": true
  }
}

Answer 3

try this:

    public class MainChatActivity extends AppCompatActivity {
    private DatabaseReference mDatabaseReference;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_chat);

        mDatabaseReference = FirebaseDatabase.getInstance().getReference();

        mSendButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                sendMessage();
            }
        });
    }

    private void sendMessage() {
        String input = mInputText.getText().toString();
        if(!input.equals("")){
            InstantMessage chat=new InstantMessage(input, mDisplayName);
            String key = mDatabaseReference.push().getKey();
            mDatabaseReference.child("messages").child(key).setValue(chat) //here you can add a Listener to check success;
            mInputText.setText("");
        }
    }
}

public class InstantMessage {
    private String message;
    private String author;

    public InstantMessage(String message, String author) {
        this.message = message;
        this.author = author;
    }

    public InstantMessage() {
    }

    public String getMessage() {
        return message;
    }

    public String getAuthor() {
        return author;
    }
}