title: How to disable button if ANY EditText is empty?
body: <p>Ive tried using TextWatcher, but if i create multiple TextWatchers(one for each EditText), the button enables when I start filling out any of the EditText.</p>
  
  <p>Example:</p>
  
  <pre><code>public class MainActivity extends AppCompatActivity {
  
      EditText numberOneEditText;
      EditText numberTwoEditText;
      EditText numberThreeEditText;
      TextView sumTextView;
  
      public void calculate(View view) {
  
  
          String numberOneString = numberOneEditText.getText().toString();
          String numberTwoString = numberTwoEditText.getText().toString();
          String numberThreeString = numberThreeEditText.getText().toString();
  
          double numberOneDouble = Double.parseDouble(numberOneString);
          double numberTwoDouble = Double.parseDouble(numberTwoString);
          double numberThreeDouble = Double.parseDouble(numberThreeString);
  
          double sum = numberOneDouble + numberTwoDouble + numberThreeDouble;
  
          sumTextView.setText(sum.getText().toString())
  
     }
  
  
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          numberOneEditText = findViewById(R.id.numberOneEditText);
          numberTwoEditText = findViewById(R.id.numberTwoEditText);
          numberThreeEditText = findViewById(R.id.numberThreeEditText);
          sumTextView = findViewById(R.id.sumTextView);
  
      }
  }
  </code></pre>