title: Subclass activity from a jar getting ClassNotFoundException
body: <p>I have two Android projects. One is a library and compiles a jar the other an executable which includes this jar on the build path. </p>
  
  <p>I'm subclassing an activity in the jar in my project but when I start it I'm getting a ClassNotFoundException.</p>
  
  <p>Here's the manifest with the activity in question being <code>MainActivity</code>:</p>
  
  <pre><code>&lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.my.package.MyProject"
      android:versionCode="1"
      android:versionName="1.0"&gt;
  
      &lt;uses-sdk android:minSdkVersion="8" /&gt;
  
      &lt;application android:label="@string/app_name"
          android:name=".MyApplication"
          android:icon="@drawable/ic_launcher"
          android:theme="@style/AppTheme"&gt;
  
          &lt;activity android:label="@string/app_name"
              android:configChanges="orientation|keyboardHidden"
              android:name=".MainActivity"&gt;
  
              &lt;intent-filter&gt;
                  &lt;action android:name="android.intent.action.MAIN" /&gt;
                  &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
              &lt;/intent-filter&gt;
          &lt;/activity&gt;
  
      &lt;/application&gt;
  
  &lt;/manifest&gt;
  </code></pre>
  
  <p>And here is my <code>MainActivity</code>, where the <code>QCARSamples</code> package is found in my jar:</p>
  
  <pre><code>package com.my.package.MyProject;
  
  import java.io.File;
  
  import com.qualcomm.QCARSamples.ImageTargets.GraphicsEngineHook;
  import com.qualcomm.QCARSamples.ImageTargets.VuforiaTrackingActivity;
  
  import com.my.package.MyProject.R;
  
  public class MainActivity extends VuforiaTrackingActivity{
      private File blenderFile;
  
      @Override
      protected synchronized void updateApplicationStatus(final int appStatus){
          return;
      }
  
      @Override
      protected GraphicsEngineHook getGraphicsEngineHook() {
          return new MyGraphicsEngineHook();
      }
  
      @Override
      protected int getSplashScreenImageResource() {
          return R.drawable.splash_screen_image_targets;
      }
  }
  </code></pre>
  
  <p>I also tried including the activity I'm subclassing in my manifest like so, but I was still getting the same error:</p>
  
  <pre><code>&lt;activity&gt;
      &lt;android:name="com.qualcomm.QCARSamples.ImageTargets.VuforiaTrackingActivity&gt;
  &lt;/activity&gt;
  </code></pre>
  
  <p>Any ideas?</p>