Android Studio : Class Not Found

Question

I am building a chat app using Firebase. When I want to test my app this error shows and the app crashes. The error is:

09-26 17:27:38.437 29482-29482/shashoug.com.zoolisd E/AndroidRuntime: FATAL EXCEPTION: main
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2309)
      at android.app.ActivityThread.access$700(ActivityThread.java:157)
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1289)
      at android.os.Handler.dispatchMessage(Handler.java:99)
      at android.os.Looper.loop(Looper.java:176)
      at android.app.ActivityThread.main(ActivityThread.java:5317)
      at java.lang.reflect.Method.invokeNative(Native Method)
      at java.lang.reflect.Method.invoke(Method.java:511)
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
      at dalvik.system.NativeStart.main(Native Method)
   Caused by: java.lang.ClassNotFoundException: Didn't find class "shashoug.com.zoolisd.MainActivity" on path: /data/app/shashoug.com.zoolisd-2.apk
      at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:65)
      at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
      at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
      at android.app.Instrumentation.newActivity(Instrumentation.java:1071)
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2171)
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2309) 
      at android.app.ActivityThread.access$700(ActivityThread.java:157) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1289) 
      at android.os.Handler.dispatchMessage(Handler.java:99) 
      at android.os.Looper.loop(Looper.java:176) 
      at android.app.ActivityThread.main(ActivityThread.java:5317) 
      at java.lang.reflect.Method.invokeNative(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:511) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869) 
      at dalvik.system.NativeStart.main(Native Method) 
09-26 17:27:40.079 29482-29482/? I/Process: Sending signal. PID: 29482 SIG: 9

Just to double check, do you have a class called `MainActivity`, and is it defined in `AndroidManifest.xml`? — Michael Dodd, Sep 26 '17 at 15:31
Try the answers outlined in this question first: https://stackoverflow.com/questions/6147241/android-app-classnotfoundexception-for-main-activity — Michael Dodd, Sep 26 '17 at 15:34
Possible duplicate of [Android app ClassNotFoundException for main activity](https://stackoverflow.com/questions/6147241/android-app-classnotfoundexception-for-main-activity) — Sufian, Sep 26 '17 at 15:41
No thing works there too, is there any chances the problem caused by Firebase? — Nazar Shashoug, Sep 26 '17 at 15:56

score -1 · Answer 1 · answered Sep 26 '17 at 15:35

-1

As it was said in earlier answers, just try:

Build - Clean project, after that
Build - Rebuild project.

Also, if it doesn't help, try File - Invalidate Caches/Restart - Invalidate.

After all of above, delete app from your device and install it again.

answered Sep 26 '17 at 15:35

Goltsev Eugene

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also I have this error 09-26 17:27:35.715 29482-29508/shashoug.com.zoolisd E/dalvikvm: Could not find class 'android.app.AppOpsManager', referenced from method com.google.android.gms.internal.zzadf.zzg – Nazar Shashoug Sep 26 '17 at 15:53
Almost always the reason was somewhere inside my project. I'm pretty sure, not Firebase is causing it. Check thoroughly that any xml file has errors. – Goltsev Eugene Sep 26 '17 at 16:07
Also check this link: https://stackoverflow.com/questions/31342684/getting-error-could-not-find-class-android-app-appopsmanager-referenced-from – Goltsev Eugene Sep 26 '17 at 16:08
If I changed my launcher activity to another activity, is there any chances it's fixed my problem? – Nazar Shashoug Sep 26 '17 at 16:16
No, I don't think so. You can just try to make your app multidex and see what happens. – Goltsev Eugene Sep 26 '17 at 16:21
Ok, I'll follow the instructions in the link – Nazar Shashoug Sep 26 '17 at 16:24
can you give me simple way to make my app a multidex? – Nazar Shashoug Sep 26 '17 at 16:47
Here is good one: https://developer.android.com/studio/build/multidex.html – Goltsev Eugene Sep 27 '17 at 07:50
that's saved my life thanks... but there' s another error : Java.lang.IllegalSateException , I think I did my themes wrong , I will define new theme that based on AppCompatTheme – Nazar Shashoug Sep 27 '17 at 14:48

Android Studio : Class Not Found

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