TextWatcher
You can do the addTextChangedListener() method one time.

First step
implements TextWatcher
Then you have a error
add unimplemented method
@Override
public void afterTextChanged(Editable s) {
}
@Override
public void beforeTextChanged(CharSequence s, int start, int count,
int after) {
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
}
Now you can need declare you editText and to add listener in onCreate()
public class MainActivity extends ActionBarActivity implements OnClickListener,TextWatcher {
EditText mEditText;
Button mButtonSave;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mButtonSave = (Button) findViewById(R.id.activity_main_button_save);
mEditText = (EditText) findViewById(R.id.activity_main_editText1);
mEditText.setOnClickListener(this);
mButtonSave.setEnabled(false);
mEditText.addTextChangedListener(this);
}
@Override
public void afterTextChanged(Editable s) {
}
@Override
public void beforeTextChanged(CharSequence s, int start, int count,
int after) {
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
if (mEditText.getText().length() == 0) {
mButtonSave.setEnabled(false);
}else{
mButtonSave.setEnabled(true);
}
}
}