The (not so) hidden cost of sharing code between iOS and Android

Until very recently, Dropbox had a technical strategy on mobile of sharing code between iOS and Android via C++. The idea behind this strategy was simple—write the code once in C++ instead of twice in Java and Objective C. We adopted this C++ strategy back in 2013, when our mobile engineering team was relatively small and needed to support a fast growing mobile roadmap. We needed to find a way to leverage this small team to quickly ship lots of code on both Android and iOS.

We have now completely backed off from this strategy in favor of using each platforms’ native languages (primarily Swift and Kotlin,

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Augmented camera previews for the Dropbox Android document scanner

With Dropbox’s document scanner, a user can take a photo of a document with their phone and convert it into a clean, rectangular PDF. In our previous blog posts (Part 1, Part 2), we presented an overview of document scanner’s machine learning backend, along with its iOS implementation. This post will describe some of technical challenges associated with implementing the document scanner on Android.

We will specifically focus on all steps required to generate an augmented camera preview in order to achieve the following effect:

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