title: ButterKnife is not binding views and causing exceptions
body: <p>I am using Butterknife(10.2.1) to bind views in a project.I recently migrated it to AndroidX. </p>
  
  <p>Though I am doing everything according to documentation here By calling </p>
  
  <pre><code>@BindView(R.id.layout_purchase_item1)
  View layoutPurchaseItem1;
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_purchase);
    ButterKnife.bind(this);
    layoutPurchaseItem1.setOnClickListener(this);
  </code></pre>
  
  <p>It is not working and giving me below exceptions:</p>
  
  <pre><code>Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
          at com.sdf.bp.billings.PurchaseActivity.onCreate(PurchaseActivity.java:108)
  </code></pre>
  
  <p>It is clear that the views are not binding here but I did nothing wrong in the layout file as just replacing binding with <code>findViewById</code> takes care of the exception. But I want to use Butterknife. Any ideas? </p>