title: android studio 0.81 cannot resolve symbol @string/hello
body: <p>I wrote a small app that worked perfectly with AS 0.6. I upgraded then to 0.81 and now I'm getting errors because of unresolved symbols in my layouts at lines like these</p>
  
  <pre><code>android:paddingLeft="@dimen/activity_horizontal_margin"
  android:paddingRight="@dimen/activity_horizontal_margin"
  android:paddingTop="@dimen/activity_vertical_margin"
  android:paddingBottom="@dimen/activity_vertical_margin
  </code></pre>
  
  <p>or this</p>
  
  <pre><code>android:text="@string/hello_world"
  </code></pre>
  
  <p>The exact error message is, e.g.</p>
  
  <p>Cannot resolve symbol '@string/hello_world'</p>
  
  <p>Those lines were inserted by AS 0.6 automatically when it created the activities and automatically defined in res/values/dimens.xml</p>
  
  <pre><code>&lt;resources&gt;
  &lt;!-- Default screen margins, per the Android Design guidelines. --&gt;
      &lt;dimen name="activity_horizontal_margin"&gt;16dp&lt;/dimen&gt;
      &lt;dimen name="activity_vertical_margin"&gt;16dp&lt;/dimen&gt;
  &lt;/resources&gt;
  </code></pre>
  
  <p>and res/values/strings.xml</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;resources&gt;
  
      &lt;string name="app_name"&gt;Points-ListView&lt;/string&gt;
      &lt;string name="button"&gt;Enter ListView&lt;/string&gt;
      &lt;string name="action_settings"&gt;Points&lt;/string&gt;
      &lt;string name="title_activity_point_list_view"&gt;PointListView&lt;/string&gt;
      &lt;string name="hello_world"&gt;Hello!&lt;/string&gt;
      &lt;string name="title_activity_point_view"&gt;PointView&lt;/string&gt;
  
  &lt;/resources&gt;
  </code></pre>
  
  <p>Does anybody know what this is due to and how to fix it? Again, no problems at all with this app when using AS 0.6. Thanks</p>
  
  <p>Edit: I updated to 0.82 and I could open another 0.6 project w/o problems, I also was able to fix the problem in 0.81 with the 0.6 project I was speaking about here by replacing the
  files</p>
  
  <pre><code>./build/intermediates/model_data.bin
  ./gradle/wrapper/gradle-wrapper.properties
  ./gradle/wrapper/gradle-wrapper.jar
  gradle.properties
  gradlew
  local.properties
  settings.gradle
  gradlew.bat
  </code></pre>
  
  <p>in the 0.6 project directory with the corresponding ones created by 0.81 for a simple "hello world" app. No clue why this worked</p>