How to set Recycler view padding on button click?

Question

Java

button_open_chat.setOnClickListener(new OnClickListener() {
            public void onClick(View view) {
                ((ConstraintLayout.LayoutParams)mMessagesRecycler.getLayoutParams()).bottomToBottom = 140;
                button_open_chat.setVisibility(View.INVISIBLE);
                sendText.setVisibility(View.VISIBLE);
                buttonSend.setVisibility(View.VISIBLE);
                sendText.requestFocus();
                InputMethodManager keyboard = (InputMethodManager)getSystemService(Context.INPUT_METHOD_SERVICE);
                keyboard.showSoftInput(sendText, 0);
    }
        });