You could add a text changed listener
first_number_from.addTextChangedListener(new TextWatcher() {
public void onTextChanged(CharSequence s, int start,int before, int count) {
if(first_number_from.getText().toString().length() == 2) {
second_number_from.requestFocus();
}
}
public void beforeTextChanged(CharSequence s, int start,
int count, int after) {}
public void afterTextChanged(Editable s) {
}
});