Android API 101

An intro to Android for non-Android devs.

Transcript

1. Aung Kyaw Paing (Vincent)
   Senior Consultant @ thoughtworks | GDE Thailand
   aungkyawpaing.dev
   Android API 101
   A intro to Android for non-Android devs
   

   View Slide

2. Android OS
   - Eventual Open source
   - Languages : Kotlin, Java & C
   - Run on Android Runtime (ART)
   - “Unused Memory is useless memory” principle
   

   View Slide

3. Android App
   - Sandboxed, every app creates it own users, i.e different
   users cannot see each other’s content
   - Unique application identifier (Reverse domain names)
   - Install via Android Package format (APK)
   

   View Slide

4. Build System
   Android officially uses Gradle as its build system. However,
   you can also use other build systems like buck build.
   

   View Slide

5. Android Components
   

   View Slide

6. ● Activities
   ● Service
   ● Broadcast Receiver
   ● Content Provider
   4 Main Components in Android API
   

   View Slide

7. Activity
   Consider this an entry point
   for your app. It holds the UI
   that the user currently sees
   

   View Slide

8. ● Entry point for background tasks
   ● Foreground services where user is aware of (music playback,
   uploading a document.. etc), cannot be killed by System.
   ● Background service where user is not aware of (syncing data quietly),
   can be killed by System
   Service
   

   View Slide

9. ● Receives events emitted by system (and other apps) such as dialing,
   low battery etc.
   ● Used mostly for alarm-based tasks or reacting to system changes
   Broadcast Receivers
   

   View Slide

10. ● Exposes data for other apps to use
    ● Used for accessing system datas such as Contacts, Media etc..
    Content Provider
    

    View Slide

11. Activating Components
    Components are activated through Intent (with the exception of
    Content Provider. Intent is the API that tells the system what the user
    wants to do.
    

    View Slide

12. //Tell system user want to view url
    val intent = Intent(Intent.ACTION_VIEW).apply {
    data = "http://www.example.com".toUri()
    }
    startActivity(intent)
    //Staring a service
    val serviceIntent = Intent(this, MyService::class.java)
    startService(serviceIntent) //or startForegroundService()
    //Register battery low events (you can also do this via Manifest)
    registerReceiver(BatteryLevelReceiver(),
    IntentFilter(Intent.ACTION_BATTERY_CHANGED))
    

    View Slide

13. Android Manifest
    

    View Slide

14. View Slide

15. Android Manifest
    An XML file that tells the OS everything about your app;
    what it is, what features does it use, what are the entry
    points… etc.
    

    View Slide

16. A typical Manifest contains
    ● Application Metadata
    ● Components Definitions
    ● Permission and Features requirements
    Android Manifest
    

    View Slide

17. android:name=".PhotoViewerActivity"
    android:exported="true">
    
    
    
    
    
    

    View Slide

18. 
    android:required="true"/>
    

    View Slide

19. APK
    

    View Slide

20. What’s inside an APK?
    - Manifest
    - DEX file (compiled code)
    - Resources
    - Assets
    

    View Slide

21. Decompile/Reverse Engineering
    https://github.com/skylot/jadx https://developer.android.com/studi
    o/debug/apk-analyzer
    

    View Slide

22. Splitting APK
    - CPU architecture
    - Screen density
    You can also generate a
    universal apk along with
    splitted apk
    

    View Slide

23. Android App Bundle
    A publishing format that contains universal codes, and let Google Play do the
    split and signing
    

    View Slide

24. APK ownership
    Each app is signed by a unique
    keystore+pass, where each keystore can
    have different alias+pass. If someone steal
    and modify the content, they cannot use
    the same keystore, and republish on
    stores and devices,
    

    View Slide

25. Google App Signing
    Instead of signing your app, you generate an upload key, and Google uses this
    key to sign you instead.
    

    View Slide

26. ● Don’t need to worry about
    losing/managing keystore file
    ● Better Security
    ● App Bundle has Instant Apps,
    Dynamic Features
    Google App Signing
    Pros
    ● How can we know for sure Google
    won’t modify the contents?
    ● Platform tied-in
    ● App Bundle causes crash in some
    devices
    Cons
    https://commonsware.com/blog/2020/09/23/uncomfortable-questions-app-signing.html
    

    View Slide

27. Android Debug Bridge
    (ADB)
    

    View Slide

28. ADB
    ADB opens a communication to your debug application.
    You can install this via brew or use android sdk
    platform-tools
    

    View Slide

29. adb pair 192.168.0.242:38157
    Wireless Debugging
    

    View Slide

30. #Push a file to Device
    adb push $FILE_IN_YOUR_PC$ $PATH_IN_YOUR_DEVICE$
    adb push ~/document.txt /sdcard/document.txt
    #Pull a file from Device
    adb pull $FILE_IN_YOUR_DEVICE$ $FILE_IN_YOUR_PC$
    adb pull /sdcard/document.txt ~/document.txt
    Transfer to/from device
    

    View Slide

31. # Input text
    adb shell input text user1
    # Input Key Events (Enter, Tab etc)
    adb shell input keyevent 61
    # Pro tips : define aliases
    alias testLogin=adb shell input text user1 && adb shell input keyevent 61 adb
    shell input text password
    Typing Text
    

    View Slide

32. Typing Text
    adb shell input text user1 && adb shell input keyevent 61 adb shell input text password
    

    View Slide

33. # Screenshot
    adb shell screencap $PATH_IN_DEVICE
    # Record video
    adb shell screenrecord $PATH_IN_DEVICE
    # Pro tips: pull screen record
    adb shell screenrecord $PATH_IN_DEVICE
    adb shell pull $PATH_IN_DEVICE
    Screenshot & Screen record
    

    View Slide

34. adb shell am start
    -W -a android.intent.action.VIEW
    -d
    adb shell am start
    -W -a android.intent.action.VIEW
    -d "https://example.com" com.google.chrome
    # Create an alias
    alias adOpenIntent=adb shell am start -W -a android.intent.action.VIEW -d
    Testing DeepLinks
    

    View Slide

35. Recap
    ● 4 main components: Activity, Service, Broadcast Receiver & Content Provider
    ● Manifest tells your app’s capabilities to the OS
    ● Never lose your keystore
    ● Weigh the pros and cons of app bundle & play app signing
    ● Utilize ADB for efficiency in your work
    (Shameless plug: https://www.aungkyawpaing.dev/useful-adb-commands/)
    

    View Slide

36. Q & A
    

    View Slide