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Fundamentals of creating Android mobile apps Scott Alexander-Bown [email protected] @scottyab

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WHO THE HECK IS THIS GUY? ➤ Senior Android Developer @ Help Scout ➤ Remote, in Bristol ➤ Google Developer Expert for Android ➤ Founder/Organiser SWMobile Meetup ➤ http://swmobile.org ➤ Co-Author Android Security Cookbook ➤ Follow on Twitter @scottyab @scottyab

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@scottyab TOO MUCH CONTENT!

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AT A GLANCE ➤Intro ➤Fundamentals ➤Android, toolkit and ecosystem ➤Android App Components ➤Development Tips ➤Don’t reinvent the wheel (use open source code) ➤What next?

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“ “Ok, Google… How do I create my first Android app” https://developer.android.com/training/basics/firstapp/

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MOBILE APPS != WEB SITE ➤ Screen size ➤ User context - maps/GPS/bluetooth/camera/accelerometer ➤ Platform integration ➤ Interaction model - glanciblity not sit down focus ➤ Intuitive (focused actions) ➤ Work offline ➤ Permissions - well defined

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ANDROID, TOOLKIT AND ECOSYSTEM

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What is Android?

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https://developer.android.com @scottyab

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@scottyab

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EMULATOR ➤ Don’t need an actual device ➤ although testing on one is recommended ➤ GPS/Cellular/Battery/Virtual sensors ➤ Screen recording/Screen shot ➤ Snap shots

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.APK AND DISTRIBUTION ➤ Android apps are packaged as .apk or .aab ➤ Signed with signing key ➤ Upload to the Play Store • $25 one off registration fee • Screen shots • Unique App Id developer.android.com/distribute/best-practices/launch/launch-checklist.html

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ANDROID COMPONENTS The core concepts and classes you’ll use on day one

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@scottyab @scottyab

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ACTIVITY ➤ AKA a Screen ➤ has distinct lifecycle ➤ onCreate() ➤ onStart() ➤ onResume() ➤ onPause() ➤ onStop() ➤ onDestory() https://play.google.com/store/apps/details?id=name.peterscully.learning.activitylifecycle @scottyab @scottyab

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RESOURCES AND LAYOUTS ➤ Layouts • Xml ➤ Values • Strings • Styles ➤ Drawables

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DESIGN XML

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INTENTS (USE FOR OPENING NEW ACTIVITIES) ➤ Action ➤ Extra ➤ Primitives ➤ Parcelables public void sendMessage(String message) {
 Intent intent = new Intent(this, DisplayMessageActivity.class);
 intent.putExtra(EXTRA_MESSAGE, message);
 startActivity(intent);
 } @scottyab @scottyab

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@Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_display_message);
 
 Intent intent = getIntent();
 String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
 
 TextView messageText = (TextView)findViewById(R.id.messageText);
 messageText.setText(message);
 }

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SERVICES ➤ Background operations ➤ Lifecycle ➤ Service ➤ Bind ➤ IntentService ➤ Work thread ➤ Start with Intent @scottyab @scottyab

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ANDROID MANIFEST.XML @scottyab

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DEVELOPMENT TIPS

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Plan on paper!

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GET OFF THE UI THREAD - ASYNCTASK ➤ Yes, there are better ways (Kotlin Coroutines, RX Java, Threadpool executor, …) ➤ But for getting started check out AsyncTask ➤ Set up ➤ onPreExecute() ➤ Do this work in the background ➤ doInBackground(arguments) ➤ Here’s the result on the main thread for you ➤ onPostExecute(result) @scottyab https://developer.android.com/reference/android/os/AsyncTask

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SAVING DATA ➤ Files (internal and external storage) ➤ SQLite ➤ Use Room persistent library a wrapper on top of SQLite ➤ Shared preferences ➤ Simple to use ➤ Combine with JSON parsing to save @scottyab https://developer.android.com/guide/topics/data/data-storage.html#pref

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MISC TIPS* ▸ Logic out of the View (i.e Activity or Fragments) ▸ Easier to test ▸ Simple architecture (MVP or MVVM) ▸ Constructor based dependancies ▸ Lock to portrait ▸ Test on real devices ▸ Min SDK 23 @scottyab * For your first app

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AVOID* ▸ RX Java ▸ Dagger ▸ Child Fragments ▸ Cross platform ▸ Bleeding edge! ▸ Jetpack Compose @scottyab * For your first app

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DON’T REINVENT THE WHEEL Dependancies & 3rd Party Libs

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GRADLE ➤ Run from CI and IDE ➤ Easy dependancy management ➤ Build variants • types • flavours

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INCLUDING DEPENDANCIES ➤ build.gradle @scottyab

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ANDROID JETPACK ➤ UI components provide widgets and helpers ➤ Architecture components help you design robust, testable and maintainable apps. ➤ Backward-compatible versions of framework components. ➤ Miscellaneous utility functions. https://developer.android.com/jetpack/ @scottyab

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CONVERT JAVA OBJECTS INTO JSON AND BACK https://github.com/google/gson API: GSON @scottyab

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T ANDROID-ARSENAL.COM

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WHAT NEXT?

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VIDEO CONTENT ➤ https://www.youtube.com/user/androiddevelopers/featured ➤ https://www.udacity.com/course/android-developer-nanodegree-by-google--nd801 ➤ @scottyab

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SAMPLE APPS ▸ github.com/android/sunflower ▸ github.com/google/iosched ▸ github.com/googlesamples/android-topeka ▸ github.com/nickbutcher/plaid ▸ github.com/chrisbanes/philm ▸ github.com/JakeWharton/u2020 ▸ github.com/googlesamples @scottyab

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https://kotlinlang.org

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@scottyab TOO MUCH CONTENT???

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THANKS swmobile.org @scottyab [email protected] QUESTIONS?

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SWMOBILE MEETUP @scottyab