Based in the requirements I understand that you are looking for an android app with file uploading, chat, video calling features. Apart from the mentioned points, app may even include User Registration, User Profile, Login.
To meet the same requirements may I also suggest the hybrid application which be built as both android and ios from same code base. The Ui, navigation, and performance would be as same as native apps. Unless you are very much particular about native apps, you can definitely consider it as a choice which turns out to be profitable as you are building two apps at the same time.
I have recently delivered a hybrid application with cool features such as meeting schedules, task management, chat, file uploads etc. The tech stack as follows: Ionic 2, Angular 2, Firebase, Node, Stripe, Twilio.
Experience details:
I have got 10+ years of web and mobile application development. Expertise in design and development of enterprise applications. Worked in multiple domains: Healthcare, telecom, manufacturing, corgo, mining, construction. Some of the Fortune listed clients I have worked with: Dignity Health, Kiewit, Rio Tinto, Etisalat, Valmont, Cosco Marine Engineering.