# Android app not running after creating a build throwing exception java.lang.ClassNotFoundException: Didn't find class "com.zipow.cmmlib.AppUtil"

**URL:** <https://devforum.zoom.us/t/android-app-not-running-after-creating-a-build-throwing-exception-java-lang-classnotfoundexception-didnt-find-class-com-zipow-cmmlib-apputil/51921>\
**Category:** Android\
**Created:** [June 7, 2021, 3:22pm UTC](https://devforum.zoom.us/t/android-app-not-running-after-creating-a-build-throwing-exception-java-lang-classnotfoundexception-didnt-find-class-com-zipow-cmmlib-apputil/51921 "2021-06-07T15:22:42Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![arifkhn46](https://avatars.discourse-cdn.com/v4/letter/a/cc9497/32.png) [@arifkhn46](https://devforum.zoom.us/u/arifkhn46)\
**Post date:** [June 7, 2021, 3:22pm UTC](https://devforum.zoom.us/t/android-app-not-running-after-creating-a-build-throwing-exception-java-lang-classnotfoundexception-didnt-find-class-com-zipow-cmmlib-apputil/51921/1 "2021-06-07T15:22:42Z")

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**Description**  
I have integrated the Zoom Client Sdk for android following official docs ([https://marketplace.zoom.us/docs/sdk/native-sdks/android/build-an-app](https://marketplace.zoom.us/docs/sdk/native-sdks/android/build-an-app)), and the app works just fine if I run it using **Android Studio (4.2)** on my phone but when I create a signed build and install it on my phone the app is throwing exception **java.lang.ClassNotFoundException: Didn’t find class "com.zipow.cmmlib.AppUtil"**

**Which Android Client SDK version?**  
v5.5.1.1319 : Latest

**To Reproduce(If applicable)**  
Steps to reproduce the behavior:

1. Create an app by referring : [https://marketplace.zoom.us/docs/sdk/native-sdks/android/build-an-app](https://marketplace.zoom.us/docs/sdk/native-sdks/android/build-an-app)
2. Create a signed build
3. Install it on your phone
4. App will throw: java.lang.ClassNotFoundException: Didn’t find class “com.zipow.cmmlib.AppUtil”

**Smartphone (please complete the following information):**

- Device: Motorola G5 S Plus
- OS: Android Version 8.1

**Additional context**  
2021-06-07 20:31:19.624 4239-4239/com.example.basicdemoapp A/zygote: java\_vm\_ext.cc:553] JNI DETECTED ERROR IN APPLICATION: JNI NewGlobalRef called with pending exception java.lang.ClassNotFoundException: Didn’t find class “com.zipow.cmmlib.AppUtil” on path: DexPathList[[zip file “/data/app/com.example.basicdemoapp==/base.apk”],nativeLibraryDirectories=[/data/app/com.example.basicdemoapp==/lib/arm, /data/app/com.example.basicdemoapp==/base.apk!/lib/armeabi-v7a, /system/lib, /system/vendor/lib]]

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**Author:** ![jon.zoom](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/jon.zoom/32/13495_2.png) [@jon.zoom](https://devforum.zoom.us/u/jon.zoom)\
**Post date:** [June 7, 2021, 9:30pm UTC](https://devforum.zoom.us/t/android-app-not-running-after-creating-a-build-throwing-exception-java-lang-classnotfoundexception-didnt-find-class-com-zipow-cmmlib-apputil/51921/2 "2021-06-07T21:30:34Z")

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Hi @arifkhn46, thanks for the post.

Am I correct in assuming you are using proguard in your project? If so, you should be able to resolve this issue by adding the following rules to your proguard config:

```auto
-keep class us.zoom.**{*;}
-keep class com.zipow.**{*;}
-keep class us.zipow.**{*;}
-keep class org.webrtc.**{*;}
-keep class us.google.protobuf.**{*;}
-keep class com.google.crypto.tink.**{*;}
-keep class androidx.security.crypto.**{*;}

```

Thanks!

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<div class="post-metadata">

**Author:** ![arifkhn46](https://avatars.discourse-cdn.com/v4/letter/a/cc9497/32.png) [@arifkhn46](https://devforum.zoom.us/u/arifkhn46)\
**Post date:** [June 8, 2021, 2:16am UTC](https://devforum.zoom.us/t/android-app-not-running-after-creating-a-build-throwing-exception-java-lang-classnotfoundexception-didnt-find-class-com-zipow-cmmlib-apputil/51921/3 "2021-06-08T02:16:32Z")

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Thanks! @jon.zoom the provided solution works. I did not found this in the official docs, and if it isn’t there then it should be mentioned.

I was wondering does it impact the app size, any thoughts?

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<div class="post-metadata">

**Author:** ![jon.zoom](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/jon.zoom/32/13495_2.png) [@jon.zoom](https://devforum.zoom.us/u/jon.zoom)\
**Post date:** [June 8, 2021, 5:06pm UTC](https://devforum.zoom.us/t/android-app-not-running-after-creating-a-build-throwing-exception-java-lang-classnotfoundexception-didnt-find-class-com-zipow-cmmlib-apputil/51921/4 "2021-06-08T17:06:01Z")

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Glad to hear it’s working!

We can definitely consider adding this to our existing documentation, thank you for the suggestion. 🙂

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**Author:** ![system](https://us1.discourse-cdn.com/flex016/uploads/zoomdeveloper/original/3X/6/1/614bdd549b610bbaa46ff934617683a02bdaa03c.png) [@system](https://devforum.zoom.us/u/system)\
**Post date:** [July 9, 2021, 3:06am UTC](https://devforum.zoom.us/t/android-app-not-running-after-creating-a-build-throwing-exception-java-lang-classnotfoundexception-didnt-find-class-com-zipow-cmmlib-apputil/51921/5 "2021-07-09T03:06:11Z")

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Closed on July 9, 2021, 3:06am UTC

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