Android development using the Eclipse IDE was once a common setup before Android Studio became the go-to development environment. Despite being largely outdated by today's standards, some developers still use Eclipse with the Android Development Tools (ADT) plugin for legacy projects. One common issue encountered in this setup is the error message: "Could not find *.apk," which suggests that the APK (Android Package) file hasn't been generated or located as expected.

Understanding the Problem

When building an Android application in Eclipse, the IDE is responsible for compiling your source code and resources into an APK file. This APK can then be installed and run on an Android device or emulator. The error message "Could not find *.apk" typically indicates a build process failure, leaving the developer without the essential output file.

Potential Causes and Solutions

1. Build Path and Project Configuration Issues

• Source Folders & Build Path: Ensure all the correct source folders are included in the build path. Misconfigured build paths can prevent the compiler from finding necessary resources.
• Project Properties: Verify the project properties. Navigate to `Properties -> Java Build Path` and check for any missing libraries or incorrect configuration.
• Android SDK: Confirm that the correct Android SDK is set in the Eclipse preferences. Go to `Window -> Preferences -> Android` and ensure the path to the SDK is set correctly.

2. ADT Plugin Issues

• Outdated ADT Plugin: Use the latest version of the ADT plugin compatible with your Eclipse IDE. An outdated plugin might not handle the latest build processes correctly.
• ADT Configuration: Check ADT settings under `Preferences -> Android`. Ensure all configurations are set according to your project's requirements.

3. Build Tools and Dependencies

• Build Tools Version: Ensure that the build tools version specified in your project matches the installed version in your SDK. If they're out of sync, it could result in build failures.
• Missing Dependencies: Check for any missing libraries or dependencies using the `Android Dependencies` section within `Java Build Path`.
• Gradle Scripts: Although not commonplace with Eclipse (pre-Android Studio era), verify any external scripts used in the build process that might create conflicting output paths or errors.

4. Eclipse IDE Related Issues

• Eclipse Version: Using a very outdated version of Eclipse can introduce incompatibilities. Ensure your Eclipse IDE is compatible with the ADT version.
• Workspace Issues: Try cleaning the project and rebuilding it via `Project -> Clean` and then `Project -> Build`.
• Console Output: Use the Console tab in Eclipse to identify any build errors or warnings that can give more specific insights into what's going wrong.

Debugging Further - Build Output Logs

To diagnose further, it’s essential to look at the logs generated during the build process.

• ADB Logcat: Utilize ADB (Android Debug Bridge) to gather logs when trying to run the app on devices.
• Eclipse Build Logs: Navigate to the Eclipse console for potential errors outputted during the build phase that aren’t directly highlighted by the IDE.

Summary Table

Transition to Modern Android Development

While addressing the "Could not find *.apk" error can still be relevant to maintaining older applications, it's recommended to transition to modern tools like Android Studio for any new development projects. Android Studio offers a more robust and streamlined environment with integrated support for Gradle, IntelliJ IDEA smarts, and a more active developer community. This shift also aligns with Google’s recommendations for up-to-date features and security.

By verifying your project's settings and leveraging the best support resources available, you can solve most issues related to the generation of APK files within the Eclipse environment, although considering an upgrade would ultimately benefit long-term maintenance and development efficiency.