Why Am I Getting a 'ClassNotFoundException' When Instantiating My Android Activity?

java.lang.ClassNotFoundException: Didn't find class on path: dexpathlist

Problem:

While attempting to instantiate an Activity in an Android application, the following exception is encountered:

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.irrlicht.example1/android.app.POMActivity}: java.lang.ClassNotFoundException: Didn't find class "android.app.POMActivity"

Analysis:

The error indicates that the specified class name, android.app.POMActivity, cannot be found in the application's runtime context. This suggests an issue with the classpath or how the Activity is declared in the manifest file.

Resolution:

To resolve this issue, check the following:

1. Ensure Class Declaration Matches: The Activity name specified in the manifest file (android.app.POMActivity) must match the actual class declaration in the Java source file (POMActivity).
2. Check AndroidManifest.xml: Verify that the Activity is declared correctly in AndroidManifest.xml, including the correct package name (com.irrlicht.example1).
3. Clean Build Cache: If the error persists after verifying the classpath, try to clean the build cache by deleting the build directory and rebuilding the project.
4. Disable Instant Run: Instant run is a feature that can sometimes cause classpath issues. Try disabling Instant Run by going to File > Settings > Build, Execution, Deployment > Instant Run > Uncheck "Enable Instant Run". Build and run the application again.
5. Check Classpath: Use a tool like JADX to inspect the generated .dex file and ensure that the Activity class is present in the classpath.
6. Update Android SDK: If the issue is still not resolved, try updating the Android SDK and ensure that the project is built against the latest version.

By following these steps and checking the specific configuration of your project, you can resolve the "ClassNotFoundException" error and successfully instantiate the Activity.

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