Don‘t Panic MOBILE DEVELOPER‘S GUIDE TO THE GALAXY published by: Open-Xchange GmbH Olper Hütte 5f 57462 Olpe Germany www.open-xchange.com Customlytics GmbH Schönhauser Allee 167 C 10435 Berlin Germany www.customlytics.com 18th Edition November 2019 This Developer Guide is licensed under the Creative Commons BY 2.5 License. Please send your feedback, questions or sponsorship requests to: [email protected] Follow us on Twitter: @MobileDevGuide Art Direction and Design by Cornelius Haverland Sarah Duwe Editors: Marco Tabor Mladenka Vrdoljak www.mobiledevelopersguide.com Mobile Developer’s Guide Contents 1 Prologue 4 The Galaxy of Mobile by Robert Virkus 14 From Idea to Prototype by Andrej Balaz 45 Android Development by Daniel Böhrs 67 iOS Development by Swen Hutop & Dennis Kluge 83 Cross-Platform Development by Robert Virkus 91 Mobile Web by Ruadhan O'Donoghue 130 Mobile Gaming by Oscar Clark 158 Security & Privacy by Dean Churchill 173 Accessibility by Cathy Rundle 201 Testing by Marc van't Veer & Julian Harty 223 Monetization by Linda Harnisch 241 App Store Optimization (ASO) by Laura Spikermann 259 User Acquisition and Retargeting by Christian Eckhardt 281 Mobile Customer Relationship Management (mCRM) by Christian Eckhardt 297 Mobile Analytics & User Feedback by Linda Harnisch 315 Epilogue 317 About the Book Prologue The edition you are holding in your hands is the very first one that has been co-published together with Customlytics. We at Open-Xchange are happy to have found a partner that shares our goals and that allows us to continue printing hardcopies to provide our little book to an even larger audience. Most importantly, this partnership has a hugely positive impact on the content of the Mobile Developers Guide. Readers of previ- ous editions will notice that the chapters about user analytics and monetization have seen massive updates and that we added new chapters covering topics like app store optimiza- tion, user acquisition and retention. In our opinion, covering these topics in depth was overdue. As the industry grows and changes, it has become clear that developing an app is just one part of the adventure. No matter how good your piece of software might be, you will not succeed without at least some knowledge about how to market it. We hope our guide helps you to learn and build upon this knowledge. Mobile marketing has become highly data-driven these days. There are numerous 3rd party tools that allow you to, for example, attribute installs to their respective source properly and enable marketers to capture a huge range of user data at particular stages in their marketing campaigns. Before we proceed, we want to issue a word of caution to our readers when it comes to handling this (user) data. We advocate for a responsible way of collecting, storing and handling user data, which respects users´ right for privacy and which is in-line with the latest legal requirements such as GDPR. Throughout the book, especially in the marketing chapters, you will notice the reference to the use of these tools from time to time. 1 Prologue We make the case that using SDKs of independent 3rd party tool providers - in contrast to certain other “data hunters”- will give app developers sovereignty and control over their data. You can read more on this in the mobile analytics chapter. Of course, you will also still find tons of updated informa- tion about how to create mobile software that is worth the marketing effort. So make sure to read all the chapters and understand how to convert your idea into code. Once you are finished reading this edition of the Mobile Developers Guide, we would like to hear your feedback. Please let us know what content you think we may have missed or where you see room for improvement. Or, even better, get involved and share your knowledge by becoming a contributor for the next edition. Cheers, Marco / Open-Xchange & Christian / Customlytics Bremen & Berlin November 2019 PS: Please follow us on Twitter @MobileDevGuide and visit mobiledevelopersguide.com to obtain the electronic edition of this booklet. PPS: As usual, the articles reflect the opinions of the respective authors. 2 Prologue The Galaxy of Mobile Robert Virkus BY Looking back into the past, the mobile scene looked a bit like the home computer ecosystem in the 1980s: many players, many operating systems, lots of innovation and changes. Today we are dealing with a global duopoly: 98% of today's mobile devices are running either on Android or iOS1. Will this change? Without political pressure or a paradigm shift we do not expect the situation to change for the foreseeable future. Looking at the details, however, reveals an exciting micro-cosmos of options, challenges & opportunities. Notable Players You should watch the following players carefully, obviously depending on your market strategy and app/game/service category. Of course, each of these players bring way more to the table than just the mentioned products and services, but these are the most relevant in the mobile segment that we cover in this guide. Some of these players form global digital leaders summarized by the GAFAM acronym, which stands for Google-Apple-Facebook-Amazon-Microsoft. Google In the mobile industry Google's Android operating system remains the major smartphone player - both by numbers and by revenue. Android has many variants like Android Go for lower end smartphones, Android One promising regular security updates 1 76% Android, 22% iOS, see gs.statcounter.com/os-market-share/mobile/ worldwide/2019 4 The Galaxy of Mobile for three years and OS updates for two years2, Wear OS for smartwatches and Android TV for smart TVs, and an integration option for cars called Android Auto. Then there is of course AOSP - the Android Open Source Project3-, which provides the core Android OS platform without the proprietary Google services. AOSP is used mostly in China but also forms the basis for LineageOS. Additionally, Google taps into the emerging game streaming market with Stadia and has established a solid share of the smart speaker market with Google Home and Google Assistant- equipped devices from other vendors. With Chrome OS Google also established itself as an important PC operating system vendor. After Amazon and Microsoft, Google is the third biggest cloud service provider. Last but not least, Google launched with Flutter4 a cross- platform framework that spans across Android, iOS, Windows, macOS and the web. Flutter also powers UI development on its future research microkernel-based OS called Fuchsia5. Apple Apple single-handedly created the smartphone market in the first place with the iPhone and specifically with the iOS operating system and the App Store in 2007 and 2008 respectively. Apple is also a leading tablet provider6 and leads 2 android.com/intl/en/one 3 source.android.com 4 flutter.dev 5 fuchsia.dev 6 As of July 2019, iPads held 70% of the global tablet market: gs.statcounter. com/os-market-share/tablet/worldwide/2019 5 The Galaxy of Mobile the smartwatch market with its Apple Watch product7. Last but not least they also have a solid multimedia offering based on the Apple TV with its tvOS. Compared with Android, Apple has a comparatively smaller but very lucrative market share. Samsung Being the biggest smartphone vendor, Samsung influences the market to a large degree. Samsung is running Android mostly, but they also work on the Tizen operating system - however, so far every attempt to establish this OS in the smartphone segment has failed. With DeX (Desktop eXperience)8 Samsung fuses the tablet and PC market by supporting keyboard, mouse and external monitors to work with selected hardware like the Samsung Galaxy Note 10 handset. Samsung also operates the Galaxy Store for app distribution which can be an attractive alternative to the Google Play Store. 7 According to Strategy Analytics, Apple's smartwatch market share in Q2 2019 was 46%: bit.ly/2MkTFzK 8 samsung.com/global/galaxy/apps/samsung-dex 6 The Galaxy of Mobile Huawei Huawei has grown to become the second largest smartphone vendor. Same as for Samsung Huawei is using the official Google-Android for the international market. Possibly the US administration triggered a new wave of innovation by forcing Huawei to move away from the Google- approved Android OS. Huawei presented its own operating system called Harmony to the public in August 2019. This is aimed to run on a Microkernel but the initial release relies on a traditional Linux kernel. With App Gallery, Huawei also operates its own app distribution platform, which can be an attractive alternative to Google Play. Facebook Facebook provides the leading mobile messaging systems with WhatsApp, Facebook Messenger and Instagram. FB Messenger specifically provides easy extension options for developers while Instagram recently introduced an AR extension called Spark AR Studio. Facebook is also the main player of the Libra cryptocurrency project and provides various other developer tools. Rightfully Facebook is under pressure for its various data and privacy breaches. Amazon Amazon is the leading smart speaker provider with Alexa, which is extensible using skills. Amazon also uses its own Android variant FireOS9 for its tablets and provides its own Android app distribution platform Amazon Appstore. Amazon also provides the leading cloud platform with AWS. 9 developer.amazon.com/de/android-fireos 7 The Galaxy of Mobile Microsoft Microsoft is still the leading desktop operating system provider but failed to get traction with its Windows Phone and subsequent mobile offerings. Still, the desktop and gaming market make Windows and Xbox attractive targets for develop- ers. Microsoft also cooperates with Sony on the emerging game streaming market using its own Azure cloud platform.