title: Default Activity Not Found - Bug in Android Studio 3.3
body: <p>When I create a new project in Android Studio 3.3, it shows an error at <code>Run -&gt; Edit Configurations</code> saying </p>
  
  <blockquote>
    <p>default activity is not found.</p>
  </blockquote>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;android.support.constraint.ConstraintLayout
          xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:tools="http://schemas.android.com/tools"
          xmlns:app="http://schemas.android.com/apk/res-auto"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          tools:context=".MainActivity"&gt;
  
      &lt;TextView
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:text="Hello World!"
              app:layout_constraintBottom_toBottomOf="parent"
              app:layout_constraintLeft_toLeftOf="parent"
              app:layout_constraintRight_toRightOf="parent"
              app:layout_constraintTop_toTopOf="parent"/&gt;
  
  &lt;/android.support.constraint.ConstraintLayout&gt;
  </code></pre>
  
  <p>This is my <strong>activity_main.xml</strong> file. It shows an error in line</p>
  
  <pre><code>tools:context=".MainActivity"
  </code></pre>
  
  <p>saying </p>
  
  <blockquote>
    <p>Unresolved Class MainActivity</p>
  </blockquote>
  
  <p>Here is my <strong>AndroidManifest.xml</strong> file - everything seems to be all right here -</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.android.myapplication"&gt;
  
  &lt;application
          android:allowBackup="true"
          android:icon="@mipmap/ic_launcher"
          android:label="@string/app_name"
          android:roundIcon="@mipmap/ic_launcher_round"
          android:supportsRtl="true"
          android:theme="@style/AppTheme"&gt;
      &lt;activity 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>The files <strong>colors.xml</strong> , <strong>ic_launcher_background.xml</strong>, and <strong>ic_launcher_foreground.xml</strong> are not correctly formed, and look something like this -</p>
  
  <pre><code>        f
  
          isInitialized
          kotlin
          Boolean
          reflect
  
          KProperty0
          SinceKotlin
          version
          1.2
          internal
  
          InlineOnly0
  
  
  
  
  
  
               4"  8�H PX��     (�    �
  </code></pre>
  
  <p>I tried to <code>Clean and Rebuild</code> project, which gave an error saying </p>
  
  <blockquote>
    <p>colors.xml is not formed properly.</p>
  </blockquote>
  
  <p>I tried <code>File -&gt; Invalidate Caches/Restart</code>, but it still shows the same error. </p>
  
  <p>This problem started one day after updating <code>Android Studio 3.2.1</code> to <code>Android Studio 3.3</code>. It worked all fine the first day, but when I tried run an app on the second day, it started showing this error saying <code>Default Activity not found</code>.</p>
  
  <p>Is there any way to fix this issue and continue using Android Studio version 3.3?</p>
  
  <p><strong>EDIT -</strong></p>
  
  <p>Yay! As @Andreas suggested, my Android Studio itself could've been corrupted, and works all right after uninstalling and reinstalling the same version (I did not even revert to an older version). Should check if this problem might repeat again in a few days.</p>
  
  <p><strong>EDIT 2-</strong></p>
  
  <p>I'm viewing this after an year and I'm happy it has helped a lot of people. Turns out this problem can arise due to various issues, and there's no one perfect answer for this. So check all the answers and see if something works for you if you're facing the same problem :)</p>