title: not assignable to 'android.app.activity' extends application
body: <p>I am implementing Adobe Creative SDK. I am getting the following error in in my my manifest file:  </p>
  
  <pre><code>'com.example.nick.avierytest2.MainActivity is not assignable to android.app.activity' 
  </code></pre>
  
  <p>This is my XML file:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  </code></pre>
  
  <p></p>
  
  <pre><code>&lt;application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:supportsRtl="true"
      android:theme="@style/AppTheme" &gt;
      &lt;activity
          android:name=".MainActivity"
          android:label="@string/app_name"
          android:theme="@style/AppTheme.NoActionBar" &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;
  </code></pre>
  
  <p></p>
  
  <p>This is my main activity class:</p>
  
  <pre><code>public class MainActivity extends Application implements IAdobeAuthClientCredentials {
  
  /* Be sure to fill in the two strings below. */
  private static final String CREATIVE_SDK_CLIENT_ID = "";
  private static final String CREATIVE_SDK_CLIENT_SECRET = "";
  
  @Override
  public void onCreate() {
      super.onCreate();
      AdobeCSDKFoundation.initializeCSDKFoundation(
              getApplicationContext(),
              AdobeAuthIMSEnvironment.AdobeAuthIMSEnvironmentProductionUS
      );
  }
  
  @Override
  public String getClientID() {
      return CREATIVE_SDK_CLIENT_ID;
  }
  
  @Override
  public String getClientSecret() {
      return CREATIVE_SDK_CLIENT_SECRET;
  }
  </code></pre>
  
  <p>}</p>
  
  <p>Every other time I have seen this question on stackoverflow it was someone trying to declare a fragment in the manifest but that is not the problem here and I have not been able to find the solution.</p>
  
  <p>Thank you for your help.</p>