Android Introduction Talk
- 2. AGENDA ▸ Facts about Android ▸ Basic Building Blocks of Apps ▸ HelloAndroid-App
- 3. WHO IS THAT GUY? ▸ CS student with focus on Machine Learning & AI ▸ Freelance app developer ▸ Recipient of Google scholarship to learn Android at Udacity
- 5. How many active Android devices? 2 billion
- 6. Market Share in Mobile OS 87.7 %
- 7. Number of Apps in Google Play > 2 million
- 9. LARGE COMMUNITY ▸ Developers ▸ Open-Source projects ▸ Libraries
- 10. ANDROID SYSTEM
- 11. ANDROID SYSTEM ▸ Linux kernel ▸ Applications are abstracted from that - no need to worry about lower layers ▸ Apps use Gradle as a build system ▸ Java & Kotlin as official languages for developing Apps
- 14. BUILDING BLOCKS ▸ Activities ▸ Services ▸ BroadcastReceivers ▸ ContentProviders
- 15. ACTIVITIES ▸ An Activity is the screen that the user sees ▸ Basis of user interaction ▸ They have a „lifecycle“ ▸ Fragments are tiny Activities with own purpose
- 16. SERVICES ▸ Some tasks require to run in background ▸ AsyncTask is able to run when app is active ▸ Services can run even when the App is not opened
- 17. WHEN TO USE A SERVICE? ▸ Rule of thumb to distinguish between AsyncTask and Services: ▸ AsyncTask —> quick (< 1 second), inside the app (e.g. download user avatar, update UI from background) ▸ Service —> longer (> 1 second), also when app closes (e.g. download mp3 in background)
- 18. BROADCAST RECEIVERS ▸ Broadcast = message sent when „events of interest“ occur ▸ Can be inside of your app or between Apps ▸ Can also be sent by the system (e.g. incoming phone call) ▸ You can either publish or subscribe to Broadcasts
- 19. CONTENT PROVIDER ▸ Best practice to store data ▸ Makes it possible to share data between apps ▸ provides an interface to easily manage different kinds of data (SQLite databases, video, audio, etc.)
- 20. ACTIVITIES
- 22. WHAT DOES IT DO? ▸ What the user sees and interacts with ▸ Shows information to your user ▸ Responds to input from your user
- 23. WHAT ARE ACTIVITIES MADE OFF? ▸ Java (or Kotlin) file for the logic and interaction ▸ Interface (.xml) file for defining what the user sees
- 24. WHAT ARE ACTIVITIES MADE OFF? ▸ Java (or Kotlin) file for the logic and interaction ▸ Interface (.xml) file for defining what the user sees
- 25. JAVA PART OF ACTIVITY ▸ Indicates which user interface is used ▸ Manages user input ▸ Responds to the activity lifecycle
- 28. LIFECYCLE LITE ▸ System tells you the state of your activity ▸ When app is started —> Activity created onCreate() ▸ When it is shown on screen —> Activity started onStart()
- 29. LIFECYCLE LITE (CONT’D) ▸ When no longer in foreground —> Activity paused (and resumed) onPause() —> onResume() ▸ When no longer visible —> Activity stopped (and restarted) onStop() —> onRestart() ▸ When it is shut down —> Activity destroyed onDestroy()
- 30. WHAT ARE ACTIVITIES MADE OFF? ▸ Java (or Kotlin) file for the logic and interaction ▸ Interface (.xml) file for defining what the user sees
- 31. INTERFACE PART OF ACTIVITY ▸ Layout file format is .xml ▸ offers a visual editor ▸ creates the layout of the screen with building blocks ▸ showing text —> TextView ▸ show image —> ImageView ▸ let the user input text —> EditText ▸ ordering of blocks is done via layouts
- 33. HOW TO BUILD AN INTERFACE? ▸ All building blocks are Views ▸ Views have properties like: ▸ id ▸ width ▸ height
- 37. HOW TO MANAGE ALL THOSE VIEWS? ▸ Views are bundled together in ViewGroups (fun fact: these are groups of views) ▸ Layout types define the order of elements in ViewGroups
- 38. COMMON LAYOUTS ▸ LinearLayout ▸ RelativeLayout ▸ ConstraintLayout
- 39. COMMON LAYOUTS (CONT’D) ▸ Different kinds of List layouts ▸ RecyclerViews (not a real layout but important) ▸ ListView ▸ GridView
- 40. HOW CAN WE START OTHER ACTIVITIES? ▸ Intents are used (can be thought of like envelopes) ▸ On creation of intent specify Activity (here „ActivityB“) to start and then start it:
- 41. WE CAN ALSO PASS DATA WITH INTENTS ▸ Data is put into Intent with an id by Activity A: ▸ Can be accessed with id by Activity B:
- 44. WHAT TOOLS ARE WE USING? ▸ We use the Android SDK ▸ We use Android Studio ▸ Generates .apk (Android Package) which can be installed on device
- 45. Live-Coding
- 47. ▸ Android Developer Portal: https://developer.android.com/ ▸ Android Trainings in the Developer Portal: https://developer.android.com/training/basics/firstapp/ index.html
- 48. ▸ Slides for Beginners (also from Google): https://drive.google.com/drive/u/0/folders/ 0B5Kg0X0yIQ1Pbk5yVGdsSFFjR28 ▸ Free courses on Udacity: https://de.udacity.com/courses/android
- 49. Thanks! On to the Codelabs…