Flutter crashes on startup: Didn't find class .MainActivity on path DexPathList

Question

I'm using Flutter with the MultiDex builder enabled for Android and encountered a pretty tricky issue. My app was running without any exceptions but when the video_player package was added it just crashed on startup:

FATAL EXCEPTION: main
Process: com.rsg.anygoal, PID: 5883
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.rsg.anygoal/com.rsg.anygoal.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "com.rsg.anygoal.MainActivity" on path: DexPathList[[zip file "/data/app/com.rsg.anygoal-tCKWlQXJD-iwdHtVRl0qqA==/base.apk"],nativeLibraryDirectories=[/data/app/com.rsg.anygoal-tCKWlQXJD-iwdHtVRl0qqA==/lib/x86, /data/app/com.rsg.anygoal-tCKWlQXJD-iwdHtVRl0qqA==/base.apk!/lib/x86, /system/lib, /vendor/lib]]
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2679)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
    at android.app.ActivityThread.-wrap11(Unknown Source:0)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6494)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
 Caused by: java.lang.ClassNotFoundException: Didn't find class "com.rsg.anygoal.MainActivity" on path: DexPathList[[zip file "/data/app/com.rsg.anygoal-tCKWlQXJD-iwdHtVRl0qqA==/base.apk"],nativeLibraryDirectories=[/data/app/com.rsg.anygoal-tCKWlQXJD-iwdHtVRl0qqA==/lib/x86, /data/app/com.rsg.anygoal-tCKWlQXJD-iwdHtVRl0qqA==/base.apk!/lib/x86, /system/lib, /vendor/lib]]
    at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:125)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
    at android.app.Instrumentation.newActivity(Instrumentation.java:1174)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2669)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
    at android.app.ActivityThread.-wrap11(Unknown Source:0) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
    at android.os.Handler.dispatchMessage(Handler.java:106) 
    at android.os.Looper.loop(Looper.java:164) 
    at android.app.ActivityThread.main(ActivityThread.java:6494) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 

Later while investigating the issue I tried to disable MultiDex and that seemingly fixed it, but then adding additional flutter package broke the app again, so I decided it's not strictly caused by multiDex and re-enabled it.

Another fix attempt I found in forums was to rename ".MainActivity" to the exact class path "com.*...*.MainActivity" but that did not help either.

Hopefully someone will suggest a possible fix to this! Leaving a few more logs and code snippets I collected during my investigation, which may include clues helpful to you.

Full Android logcat logs: https://pastebin.com/vPs614jj

Flutter pubspec (name and description intentionally omitted):

version: 1.0.6+16
environment:
  sdk: ">=2.1.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter
  cupertino_icons: ^0.1.2
  intl: ^0.15.8
  firebase_core: ^0.4.3+1
  firebase_admob: ^0.9.0+10
  firebase_analytics: ^5.0.9
  firebase_auth: ^0.15.3
  firebase_crashlytics: ^0.1.2+4
  firebase_performance: ^0.3.1+5
  firebase_remote_config: ^0.3.0+1
  firebase_messaging: ^6.0.9
  firebase_dynamic_links: ^0.5.0+9
  cloud_firestore: ^0.13.0+1
  cloud_functions: ^0.4.1+6
  google_sign_in: ^4.1.1
  provider: ^4.0.1
  data_connection_checker: ^0.3.4
  shared_preferences: ^0.5.6
  flutter_markdown: ^0.3.2
  url_launcher: ^5.4.1
  barcode_scan: ^1.0.0
  qr_flutter: ^3.2.0
  share: ^0.6.3+5
  video_player: ^0.10.11+2

dev_dependencies:
  flutter_test:
    sdk: flutter

flutter:
  fonts:
    - family: Raleway
      fonts:
        - asset: fonts/Raleway-Regular.ttf
  uses-material-design: true

Android Manifest:

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="$APP_DOMAIN">
    <application android:name="io.flutter.app.FlutterApplication" android:label="$APP_NAME" android:icon="@mipmap/ic_launcher">
        <activity android:name=".MainActivity" android:launchMode="singleTop" android:theme="@style/LaunchTheme" android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode" android:hardwareAccelerated="true" android:windowSoftInputMode="adjustResize">
            <meta-data android:name="io.flutter.app.android.SplashScreenUntilFirstFrame" android:value="true" />
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
            <intent-filter>
                <action android:name="FLUTTER_NOTIFICATION_CLICK" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
        <meta-data android:name="com.google.android.gms.ads.APPLICATION_ID" android:value="$APP_ADS_ID"/>
        <meta-data
            android:name="com.google.firebase.messaging.default_notification_icon"
            android:resource="@drawable/notification_icon" />
    </application>

    <uses-permission android:name="android.permission.INTERNET"/>
</manifest>

MainActivity.java:

import android.os.Bundle;
import io.flutter.app.FlutterActivity;
import io.flutter.plugins.GeneratedPluginRegistrant;

public class MainActivity extends FlutterActivity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    GeneratedPluginRegistrant.registerWith(this);
  }
}

Flutter doctor output (XCode shouldn't matter):

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.17.5, on Mac OS X 10.15.4 19E287, locale en-BG)
 
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
[!] Xcode - develop for iOS and macOS
    ✗ Xcode installation is incomplete; a full installation is necessary for iOS development.
      Download at: https://developer.apple.com/xcode/download/
      Or install Xcode via the App Store.
      Once installed, run:
        sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer
        sudo xcodebuild -runFirstLaunch
[✓] Android Studio (version 3.5)
[✓] VS Code (version 1.46.1)
[✓] Connected device (1 available)

Answer 1

I had similar error, after a "package name" change. My solution was: Update package name also in MainActivity.kt.

In short, all package names should be fixed accordingly.

after that, it is fixed.

Answer 2

My findings suggest this is not an issue with Flutter itself, but occurs after particular Flutter package installations. After upgrading Gradle and the AndroidX libraries, the crash disappeared and then re-appeared after another Flutter package addition. Then I cleaned (build->clean in the IDE) the android project again and it was fixed once again. So it may be due to some Gradle confusions in my environment and probably it just doesn't compile some classes the right way from time to time.