Android - usage of TextWatcher

final TextView textMsg = (TextView) findViewById(R.id.textviewTicketNo);
TextWatcher textWatcher = new TextWatcher() {

    @Override
    public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {
        textMsg.setText("Processing...");
    }

    @Override
    public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
    }

    @Override
    public void afterTextChanged(Editable editable) {
    // get text value from textbox (txtScanningInfo)
    // start processing when detect certain char ('\n')
    }
};
txtScanningInfo.addTextChangedListener(textWatcher);