title: Can't create custom setters for android data binding - "Could not find accessor" error
body: <p>I'm trying to create custom setter as described here:
  <a href="https://developer.android.com/tools/data-binding/guide.html#custom_setters" rel="nofollow">https://developer.android.com/tools/data-binding/guide.html#custom_setters</a></p>
  
  <p>My view is:
      </p>
  
  <pre><code>&lt;data&gt;
          &lt;variable name="viewModel"
          type="com.example.feed.DummyViewModel" /&gt;
  &lt;/data&gt;
  
      &lt;LinearLayout
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:orientation="vertical"&gt;
  
          &lt;ImageView
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              app:imageUrl="@{viewModel.imageUrl}" /&gt;
      &lt;/LinearLayout&gt;
  &lt;/layout&gt;
  </code></pre>
  
  <p>Binding is:</p>
  
  <pre><code>package com.example.feed;
  
  import android.databinding.BaseObservable;
  import android.databinding.BindingAdapter;
  import android.widget.ImageView;
  
  public class DummyViewModel extends BaseObservable {
  
      @BindingAdapter("bind:imageUrl")
      public static void loadImage(ImageView view, String url) {
  // nothing yet
      }
  }
  </code></pre>
  
  <p>Wen building I get error:</p>
  
  <pre><code>Error:Execution failed for task ':app:compileDebugJavaWithJavac'.
  &gt; java.lang.RuntimeException: Found data binding errors.
   ****/ data binding error ****msg:Could not find accessor com.example.feed.DummyViewModel.imageUrl file:/Users/tse/t/app/src/main/res/layout/fragment_main.xml loc:20:28 - 20:45 ****\ data binding error ****
  </code></pre>
  
  <p>What is wrong with my <code>loadImage</code> function? How to make correct binding adapter?</p>