Как преобразовать keycode в char или string?
Вот пример кода:
public boolean onKey(View v, int keyCode, KeyEvent event) {
    // TODO Auto-generated method stub
    //Log.d("EditText", "It Working...!" + event.getAction());
    if (event.getAction() == 0) {
        switch (v.getId()) {
        case R.id.editText1:
            Log.d("EditText", "In editText1");
            if (text1.length() == 3)
            {
                text2.setText();
                text2.requestFocus();
            }
            break;
        case R.id.editText2:
            Log.d("EditText", "In editText2");
            if (text2.length() == 0)
                text1.requestFocus();
            break;
        }
    }
    return false;
}