title: Can't change InputType method in EditText
body: <p>I need to on the start of the <code>Activity</code> my <code>EditText</code> has the <code>readonly</code> mode so I do it like below:<br>
  <strong>xml</strong>  </p>
  
  <pre><code>&lt;layout xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:app="http://schemas.android.com/apk/res-auto"&gt;
  
      &lt;android.support.design.widget.CoordinatorLayout
          android:layout_width="match_parent"
          android:layout_height="match_parent"&gt;
  
          &lt;android.support.design.widget.TextInputLayout
              android:layout_width="match_parent"
              android:layout_height="0dp"
              android:layout_weight="1"
              android:paddingBottom="@dimen/edge_offset"
              android:paddingLeft="@dimen/edge_offset"
              android:paddingStart="@dimen/edge_offset"
              android:paddingRight="@dimen/edge_offset"
              android:paddingEnd="@dimen/edge_offset"
              android:paddingTop="@dimen/edge_offset"
              app:layout_behavior="@string/appbar_scrolling_view_behavior"&gt;
  
              &lt;EditText
                  android:id="@+id/hometask_edt"
                  android:layout_width="match_parent"
                  android:layout_height="match_parent"
                  android:inputType="textMultiLine"
                  android:gravity="top|start"
                  android:scrollHorizontally="false"
                  android:hint="@string/label_summary"/&gt;
  
          &lt;/android.support.design.widget.TextInputLayout&gt;
  
      &lt;/android.support.design.widget.CoordinatorLayout&gt;
  
  &lt;/layout&gt;
  </code></pre>
  
  <p><strong>Activity</strong>  </p>
  
  <pre><code>@Override
  protected void onCreate(@Nullable Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      mBinder = DataBindingUtil.setContentView(this, R.layout.activity_hometask);
      // Setup EditText
      mBinder.hometaskEdt.setInputType(InputType.TYPE_NULL);
  }
  </code></pre>
  
  <p>When the user clicks a menu item the <code>EditText</code> must be editable again. I try to make it so:</p>
  
  <pre><code>@Override
  public boolean onOptionsItemSelected(MenuItem item) {
      int itemId = item.getItemId();
  
      if (itemId == R.id.action_edit) {
          mBinder.hometaskEdt.setInputType(InputType.TYPE_CLASS_TEXT);
          mBinder.hometaskEdt.invalidate();
  
          return true;
      }
  
      return super.onOptionsItemSelected(item);
  }
  </code></pre>
  
  <p>But, of course, it doesn't work =( What do I doing wrong?</p>