Android app ClassNotFoundException for main activity

Question

Most of the devices can run my app but I got this error report :

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.company.app/com.company.app.MainActivity}: java.lang.ClassNotFoundException: com.company.app.MainActivity in loader dalvik.system.PathClassLoader[/mnt/asec/com.company.app-1/pkg.apk]
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2755)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2854)
at android.app.ActivityThread.access$2300(ActivityThread.java:136)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2179)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:143)
at android.app.ActivityThread.main(ActivityThread.java:5068)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassNotFoundException: com.company.app.MainActivity in loader dalvik.system.PathClassLoader[/mnt/asec/com.company.app-1/pkg.apk]
at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:243)
at java.lang.ClassLoader.loadClass(ClassLoader.java:573)
at java.lang.ClassLoader.loadClass(ClassLoader.java:532)
at android.app.Instrumentation.newActivity(Instrumentation.java:1034)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2747)
... 11 more

I found there is a related answer: ClassNotFoundException Android

but the question is, my exception occurs before any line of code i write, so how can I ensure the class loader is loaded?

The SD card is removed or mounted to a PC stackoverflow.com/questions/4820554/… stackoverflow.com/questions/5483947/… — Dante
– Dante, Commented Jul 22, 2011 at 8:56
The SD card is removed or mounted to a PC stackoverflow.com/questions/4820554/… stackoverflow.com/questions/5483947/… — Dante
– Dante, Commented Jul 22, 2011 at 8:57
In my case the problem was caused by updating SDK to version 22. I was able to solve this problem using this question: stackoverflow.com/questions/16585964/… — petrsyn
– petrsyn, Commented May 30, 2013 at 21:28

Arun · Accepted Answer · 2013-01-27 22:18:37Z

21

I had exactly the same problem. Suddenly my app stopped working. I didint make any change to manifest, but with some accident there was missing first row:

<?xml version="1.0" encoding="utf-8"?>

This caused ClassNotFoundException for launcher activity. I was struggling with that for few hours and I overlooked this every time I was checking manifest for possible mistake.

Strange thing happened after I have deleted this row again. Suprise, suprise app was still working. (and I didnt forget to rebuild app)

Hope this help someone to save few hours.

edited Jan 27, 2013 at 22:18

Arun

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answered Jan 27, 2013 at 22:01

Koso

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2 Comments

marzapower Over a year ago

Sadly, I am getting this exception even with that line on top of the manifest. It's kind of random, though ...

Leon Joosse Over a year ago

This answer helped me out. I also had to run gradle clean, since the old debug APK was still not correct.

fredw · Accepted Answer · 2011-05-27 04:45:59Z

11

I get this error when my class isn't correctly defined in the manifest, typically because I haven't put in the correct name space as in:

    <activity android:name="com.company.project.main.MyMainActivity" ...>

as opposed to

    <activity android:name="MyMainActivity" ...>

Not sure why it would work for you on some devices and not others though.

answered May 27, 2011 at 4:45

fredw

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5 Comments

Sandeep Dixit Over a year ago

<activity android:name=".MyMainActivity" ...>, it is correct way to define

fredw Over a year ago

good point. Although in this example if the project is com.company.project, I think it would have to be ".main.MyMainActivity"?

Sandeep Dixit Over a year ago

yes, before Activity, it takes package name, Package name is already defined in menifest

Kay Chan Over a year ago

I think fredw is trying to solve my problem but I cannot verify it so soon, as the problem only occurs at customer side.

RHaguiuda Over a year ago

This fixed for me. Thanks.

Anju · Accepted Answer · 2011-05-27 04:29:32Z

6

Please close your eclipse and open. Clean your project and do a refresh. Then run and see.

answered May 27, 2011 at 4:29

Anju

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2 Comments

Kay Chan Over a year ago

the problem only occurs at customer side. :/

cratonica Over a year ago

Not sure why this was downvoted. Restarting Eclipse fixed it for me.

luben · Accepted Answer · 2013-12-06 10:11:42Z

3

I had the same issue and the problem was a third party library that is using Android Support Library.

myproject/libs/android-support-v4.jar 
3rdpartylib/libs/android-support-v4.jar

When I updated the library with newer version, the support library was also updated - but not in my project. After that I could not launch the application with this error. After making both libraries to be the same (copy), it was ok.

answered Dec 6, 2013 at 10:11

luben

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Comments

Cristan · Accepted Answer · 2014-07-18 08:16:01Z

2

In eclipse, check Properties>Java Build Path>Source and see if the output folder is always the default (/bin/classes).

For me, this was an issue because of the maven plugin: whenever I right click>Maven>Update Project...>Ok, it changes the output folder of the src folder to target/classes, causing the ClassNotFoundException.

answered Jul 18, 2014 at 8:16

Cristan

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1 Comment

40pro Over a year ago

+1. I changed my project to Maven Project so it changed my output folder to /target/classes. Hence the class not found error - because its in the wrong path!!!

nedaRM · Accepted Answer · 2013-10-11 05:01:31Z

1

I just ran into this problem. Turns out it was because I had moved my MainActivity into a new package.

What I did was move it from

com.example.MainActivity

into

Activity

so in my manifest it looked like this:

 android:name="Activity.MainActivity"`

Solved it by moving it back into the original package. It can also be solved by renaming your packages correctly:

Eg: com.example.Activity.MainActivity

Hope this helps someone.

answered Oct 11, 2013 at 5:01

nedaRM

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Comments

Kyle O. · Accepted Answer · 2014-06-24 17:22:44Z

I had this problem for the last couple days. I could run my app on every test environment, I could export a release apk, and install and run it on every test environment, but when I uploaded the apk to the play store and installed from the play store the app would fource close throwing ClassNotFoundException. It turned out that in my project I was sending multipart form data to a web api, and to do this requires some external libraries. At first I just included all the mim4j, httpclient, and httpcore .jars (turns out to be a lot of jars).

After deleting almost all of them one by one and seeing if my project would still build I was left with only one jar THAT WAS ACTUALLY REQUIRED. The take away is delete any jars that are not required to build. Then I tested the app and turns out I needed to add one of the jars back because it's resources were referenced by the one that was required to build the project. Make sure to test every function of your app after deleting jars.

Then I went through each library project I was including and went to right-click on project -> properties -> java build path -> order and export and checked all the boxes FOR EVERY LIBRARY and MY OWN PACKAGE.

Then I did a project -> clean on every project that is included and the main project.

Then I exported the apk and put the package up for beta testing and it finally worked on users devices.

Community · Accepted Answer · 2017-05-23 12:26:23Z

1

I ran into this problem and it was fixed using this.

I had not checked one external library under "Order and export" and i was getting the error.

edited May 23, 2017 at 12:26

CommunityBot

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answered Jul 16, 2014 at 0:39

Abhinav

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Comments

Jjang · Accepted Answer · 2015-08-22 14:59:07Z

None of the answers above worked for me, contributing my solution if it's going to spare some hours to anyone in the future.

What apparently worked for me was removing an extra support lib v4 jar in my project.

After I updated the support lib via android tools, I had to fix jar mismatches in many libraries I use and point them all to the same jar in the android-sdks folder.

I accidently added it to my project as well, and for some reason it made my MainActivity class not found in runtime, because the jar was also in the android-support-v7-appcompat library I was using.

No errors on eclipse at all.

I removed the jar from my project, and checked the jar in the v7 appcompat library in the export tab so it would be available to my project as well, and voila, app is working.

NoBugs · Accepted Answer · 2014-01-05 04:06:12Z

0

Thanks to version control, I noticed that I didn't have these lines in my .classpath xml file:

<classpathentry kind="src" path="src"/>
<classpathentry kind="src" path="gen"/>

These caused Class-not-found for main activity.

answered Jan 5, 2014 at 4:06

NoBugs

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Comments

user9783351 · Accepted Answer · 2018-05-13 08:53:30Z

0

I've got the same when run Robolectric tests. Actually, test classpath includes jar with android.com.Activity, which has not been founded. A solution in my case is downgrade JAVA_HOME from 10th JDK version, which is used in Maven project.

answered May 13, 2018 at 8:53

user9783351

1

Comments

Braian Coronel · Accepted Answer · 2018-12-20 07:36:17Z

0

I made a copy/paste of the following folders to a new project, keeping the same package name, and solved it:

../src/debug
../src/main
../src/release

And finally I added the file dependencies build.gradle.

GL

answered Dec 20, 2018 at 7:36

Braian Coronel

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MR V · Accepted Answer · 2023-02-15 06:46:57Z

0

If you changed your package name in flutter using some dev dependency package you have to cross check the both area

In androidmanifest.xml => "<activity android:name="your new package name.MainActivity" 2.In mainActivity.java

edited Feb 15, 2023 at 6:46

answered Feb 7, 2023 at 6:19

MR V

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1 Comment

Community Over a year ago

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