title: MainActivity is not declared in the manifest?
body: <p>Ok, yesterday I made some changes and since then my app says that the MainActivity was not declared.
  At first, it said just "Default Activity not found" which, after trying a few decisions turned into "MainActivity is not declared.."</p>
  
  <p>This is my code:</p>
  
  <pre><code>    &lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
            package="com.example.myapplication"&gt;
      &lt;uses-permission android:name="android.permission.INTERNET"/&gt;
  
      &lt;application
              android:allowBackup="true"
              android:icon="@mipmap/ic_launcher"
              android:label="@string/app_name"
              android:supportsRtl="true"&gt;
          &lt;activity
                  android:name=".MainActivity"
                  android:label="@string/app_name"
                  android:theme="@style/AppTheme"&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>