unable to instantiate application - ClassNotFoundException

Question

EDIT: This problem has not already been resolved in the other suggested SO question

I had a fully working app on the market for over a year, with very few crash reports. Then recently I changed my app into a library, so that it could be included within multiple different "wrapper" projects. This was so that I could easily make different version - free, paid, non-google markets, with/without in-app purchasing etc etc.

The new "library+wrapper" app appeared to work fine. I could run it multiple times, without error. But then a day later (when presumably the OS had closed some or all of the app's activities) I tried to run it and it reported

Unable to instantiate application com.mycompany.mygamelibrary.MyGameApplicationClass: java.lang.ClassNotFoundException: com.mycompany.mygamelibrary.MyGameApplicationClass

The class it failed to find is the first class that runs when the program starts up, MyGameApplicationClass - which extends Application. This class is part of the library.

I suspect something goofy in one of the two manifest files.

The manifest of the wrapper project contains the lines...

<application android:icon="@drawable/mygame_icon"
    android:screenOrientation="portrait" android:label="My Game Name"
    android:name="com.mycompany.mygamelibrary.MyGameApplicationClass">

Any ideas what could have gone wrong?

EDIT: The library was referenced "the correct way" as defined by yorkw's answer to this SO question.

EDIT: I can not repeat the crash at the moment :-( I don't know what it is the OS does when the app is not used for a day or two.

Answer 1

For me the problem was that I had to specify fully qualified names for all activities and the application class in the Manifest, after upgrading AGP.

Answer 2

I ran into this problem today. The project runs well for over a year but today it reports this issue, and cannot debug on my testing device.

I fixed it by updating to latest gradle version. Hope this can solve your problem.

Answer 3

I ran into this issue several times and both times it seemed to be caused by some instant run feature.

In my case, deleting the application from the device and then installing it from Android Studio again resolved the issue.

Answer 4

This all Process work for me to solve application class Exception.

Step 1: Open Run(window+R) Search -> Prefetch Remove all file (Some file not Delete)

Step 2: Open Run(window+R) Search -> %temp% Remove all file (Some File not Delete)

Step 3: Open Android Studio -> Build -> Clean Project

OR

Select File > Invalidate Caches / Restart > Invalidate and Restart from Android Studio toolbar.

OR

Close and reopen Android project.

OR

Restart System

Answer 5

In my case, application id and package were mismatched. This should be same as presented in following images...

AndroidManifest.xml

app/build.gradle

In this case you can see, applicationId and package both are same that is com.mycompany.mygamelibrary

Answer 6

For Android Studio:

Build --> Clean Project

Fixed issue.

Answer 7

I had a slew of bugs with Android Studio 3.0 Canary 4 and the way I fixed them was by editing the AndroidManifest.xml by adding in some jibberish to the application name. Then, I clicked build. Obviously, a whole mess of new error messages appeared. I changed the name back to what it should be, built the app, and it just ran.

Sometimes, I just don't know...

EDIT: Just ran into this issue on Android Studio 3.0 Canary 4 on my laptop when switching over. I again went through the same process of changing AndroidManifest.xml file to contain a typo, building, and changing back. That didn't work.

I then noticed that instant run was still enabled. Going into settings (by clicking command + , (comma key)) and typing "instant run", I was able to disable instant run, built the app, and the error of class not found went away.

Summary of Steps to Fix [FOR ME]

1. Invalidate cache / restart
2. Clean the project
3. Manually delete the build folder (need to be in project view for this one)
4. Make an intentionally errant edit to your AndroidManifest.xml file, build the app, observe the errors, remove the errant edit and build again
5. Disable instant run

Again, I don't mean to insinuate that this will fix everyone's error, but I have now used some combination of these steps on two different machines (MacOS Sierra) and it has been resolved for me. Hope it helps.

Answer 8

I had this issue in an Android application that needed an Application class which was created in wrong path inside the Android Studio project. When I moved the class file to the correct package, it was fixed.

Answer 9

There are two possibilities. Either you, like me, have a spelling error in your manifest file. Have a co-worker or friend read it to make sure the name is correct. Or you have not referenced the project correctly.

The official document describes how to properly link projects in its documentation.

Why it would first seem to work and later stop working is a bit of a mystery. However, I guess that the VM might still have had the necessary references ready to resolve the classes in the library just fine. A restart of the VM removed all those references and trying to resolve them was unsuccessful.

Update: Regarding the edits in the OP: As you confirm that you have correctly referenced the other project, you can check if the project is included in APK, just to be sure. You can rename and open an APK as any other archive (.rar works fine for me). Sometimes, it happened to me, the project is not correctly included in the APK. A cleaning of your workspace usually remedies the problem and so could a restart of your IDE depending on what you are using. To manually conduct a clean in Eclipse for example, use Project->Clean... or try Android Tools->Fix Project Properties by right-clicking on your project.

As you seem to also have fixed the problem by restarting your device, it could be that the libraries were linked incorrectly. A problem that I have never seen myself but as a very common quote says: "Have you tried turning it off and on again?".

Answer 10

Same message seen ... this time it turned out to be different output folders for MyApp/gen and MyApp/src in the Build Path (caused by Maven integration).

Unchecking "Allow output folders for source folders" solved the problem.

Answer 11

I'm not very sure about this but it might be that your system's debug.keystore license validity has expired as it is valid for only 365 days. You just need to delete the debug.keystore from your computer. The debug.keystore will be generated automatically by Eclipse when you compile your Android App.

Answer 12

Once I had the same error message, but maybe the cause isn't the same.

I did a code and worked for a while, then I wanted to improve it and got the same error and I couldn't run it.

I could fix the problem with

• the correct Build Path order (as I can see you've already did this)
• I check on the Order and Export tab the android-suppor-v4.jar
• and the key was the Android SDK Managert->Upgrade everything and (next) Eclipse->Help->Check for updates.

After I upgraded to the latest android plugin and SDK my app compiled and ran again.

I hope this will help you!

Answer 13

Have you tried to make a new subclass of MyGameApplicationClass in your 'main' project and set it in the manifest as Application class?

Answer 14

May be its a Build Path Configuration problem.I did the following to solve the issue.

1.Right click on your project and go to Java Build Path.

2.Click on Order and Export tab.

3.Check Android Private Libraries and other 3rd part libraries if you have added.

4.Press ok and clean the project. I hope it will solve the issue.