Android Invoice Detail Extraction App

I need an Android app that opens a single-invoice Excel file and automatically pulls out the key data I care about:
• Invoice number
• Total amount
• Sender and receiver details
• All article/line items

A simple, clean UI is fine—one button to select or upload the Excel invoice and a results screen that displays the extracted fields. Storing the parsed data as JSON (and optionally allowing a CSV export) will make it easy for me to feed the information into other systems later, so please include that.

You are free to use any reliable Excel-handling or parsing library (Apache POI, JExcel, etc.) as long as it runs smoothly on recent Android versions. The final deliverable should include:
1. The compiled APK for quick testing on my phone.
2. Full, well-commented source code that builds in Android Studio.

Acceptance criteria
• Invoice opens without crash on Android 10+.
• All four data groups above are extracted accurately from the sample I provide.
• Results screen shows the raw data and offers a “Save as JSON” option.

If you have questions about the sample format or need additional test files, let me know and I’ll send them over right away.