Two-step donation kiosk app connected to a mobile POS payment terminal (Android, Java)

Android Java (not Kotlin) app delivering essentially a two-step payment process. This donation app is a self-service kiosk tablet (with Miura pinpad) that has to run 24/7. Special attention has to be paid to make sure the application does not cause memory leaks and performs error handling and reporting well. The terminal is integrated using a Java SDK that is delivered from the payment service provider (PSP), of which an example integration is available via NMI ([login to view URL]). This SDK connects to the terminal and SOAP/XML backend of the PSP. We are looking for a developer that is a confident and experienced programmer, having a good understanding of design patterns. Experience with UI/UX and payment gateways is a pro. The programmer will work under supervision in order to guarantee code quality. Programmer is fluent in English. App must: - interface with the NMI (CreditCall) Direct API (see attached) - respond to lost internet (WiFi/Ethernet) connection as well as lost terminal connection (USB) - user-friendly interact in the payment process (i.e. user cancels, payment is not delivered in time, not sufficient funds, card not accepted, thank you-message, user goes back to select a different amount, etc.) - support admin-protected area with configurable payment amounts - autonomously (re)connect with terminal, gateway, and perform TMS updates (a procedure to update the pinpad) - written with AndroidX (Jetpack) compatibility - using fragments - the code is expected to be documented well on the spots where complicated tasks are performed, but unit testing or functional tests are not required. - supports two different devices: tablet and mobile phone (different views for each device) - sophisticated UI is not required, but the overall structure needs to be there Application interface: - main screen with nicely designed buttons with the different payment amounts (1,2,5 euro, "other amount") - screen for user-configurable donation amount ("other amount") - password protected admin-screen that is accessible by touching a corner of the app a couple of time (or something of the like) - a "payment screen" to guide the user when the card has to be presented to the pinpad We are a young startup that wants to take the next step in donations, supporting churches, musea and other institutes. We are accessible and communicative. Our background is in business development and IT. If our collaboration works out well there are good prospects for future work.