안드로이드 채팅 오류확인부탁드려요~

Question

안드로이드 스튜디오로 블루투스 채팅 구현중인데

private final Handler mHandler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case MESSAGE_WRITE:
                byte[] writeBuf = (byte[]) msg.obj;
                // construct a string from the buffer
                String writeMessage = new String(writeBuf);
                mAdapter.notifyDataSetChanged();
                messageList.add(new androidRecyclerView.Message(counter++, writeMessage, "Me"));
                break;
            case MESSAGE_READ:
                byte[] readBuf = (byte[]) msg.obj;
                // construct a string from the valid bytes in the buffer
                String readMessage = new String(readBuf, 0, msg.arg1);
                mAdapter.notifyDataSetChanged();
                messageList.add(new androidRecyclerView.Message(counter++, readMessage, mConnectedDeviceName));
                break;
            case MESSAGE_DEVICE_NAME:
                // save the connected device's name
                mConnectedDeviceName = msg.getData().getString(DEVICE_NAME);
                Toast.makeText(getApplicationContext(), "Connected to "
                        + mConnectedDeviceName, Toast.LENGTH_SHORT).show();
                break;
            case MESSAGE_TOAST:
                Toast.makeText(getApplicationContext(), msg.getData().getString(TOAST),
                        Toast.LENGTH_SHORT).show();
                break;
        }
    }
};
전체 노란색 경고가 뜨네요 ㅜㅜ

왜일까요?

그리고 터미널에서 텍스트를 send하면 글자가 한글자씩 따로나오는데

그건 왜그런건지 알려주세여ㅜㅜㅜ