title: how to get the action bar button? findviewbyid seems doesn't work
body: <p>Suppose I have two buttons, one is an action button which is in the action bar(@+id/button1). And another is common button in the layout(@+id/button2). </p>
  
  <p>How can I set the button1 disabled when i click the button2?</p>
  
  <p>findViewById(button1) seems not work. it will return null.</p>
  
  <p>this is my menu xml:</p>
  
  <p><code>&lt;menu xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"&gt;
      &lt;item
          android:id="@+id/button1"
          android:title="submit"
          android:showAsAction="always" /&gt;
  &lt;/menu&gt;</code></p>
  
  <p>and this is my mainacticity:</p>
  
  <pre><code>@Override
  public boolean onCreateOptionsMenu(Menu menu) {
      MenuInflater inflater = getMenuInflater();
      inflater.inflate(R.menu.my, menu);
      return true;
  }
  @Override
  public boolean onOptionsItemSelected(MenuItem item) {
      int id = item.getItemId();
      if (id == R.id.button1 ) {
          return true;
      }
      return super.onOptionsItemSelected(item);
  }
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_my);
      button1 = (Button) findViewById(R.id.button1);/*which return null*/
      button2 = (Button) findViewById(R.id.button2);
      button2.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {
              button1.setEnabled(false);/*what i failed to do*/
          }
      });
  }
  </code></pre>