Notes - Modern Android development: Android Jetpack, Kotlin, and more (Google I/O 2018)

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本記事は、Modern Android development: Android Jetpack, Kotlin, and more (Google I/O 2018)のNotes記事です。

Android History

#

• 2008 - Android 1.0

• 2013 - Android Studio

• 2014 - ART, RecyclerView

• 2017 - ConstraintLayout, Kotlin, AAC, Studio Profilers

• 2018 - ktx, Paging

Tools

#

• Layout Inspector

• Trace View -> Systrace

• New Profiler Tab in Android Studio

• Memory Tracking

• Layout Design

  • ConstraintLayout

Runtime in Language

#

Dalvik

#

• Optimized for Space

• JIT optimizations not as powerful

• Slow Allocation/collection

• Heap fragmentation

So

#

• Avoid allocations(e.g. Don’t use Enums!)

• Primitive types are cool

ART

#

• Optimized for performance

• JIT + AOT

• Faster allocation/collection

• Heap defragmentation

• Large object heap

So

#

• Allocate as necessary(Yes, even enums)

• Use appropriate types

But

#

• Phones are still constrained

• Buttery is important

Java

#

• Started with Java 1.5

• Extremely popular

• Available great tools

• Slow adoption of newer versions

Kotlin

#

• Official support in 2017

• Close collaboration with Jetbrains

• Many great features that make code more enjoyable to write & read

• Android project can contain both Kotlin & Java

• Lint checks in Android Studio

• Java -> Kotlin conversion

• Android Kotlin Extension

• Kotlin Style Guide

• Kotlin Interop Guide

Benefits of Kotlin

#

• Extensions

• Inline functions

• Operators

• De-structuring assignments

• Data classes

• Lambdas

Now, new Java APIs in the platform starting with Android P will follow the code convention of Kotlin that when there is a SAM interface as parameter, it goes at the end of the list of parameters.

APIs

#

• AbsoluteLayout => Deprecated

• LinearLayout => Okay for simple cases

• FrameLayout => Okay

• GridLayout => Don’t use

• RelativeLayout => Don’t use

• ConstraintLayout => Use it. 2.0 Soon!

• AdapterViews

Fragments

#

• Complicated

• Core platform bugs+fixes => Core Platform API @deprecated

• Use Support Library Fragments

  • Improvements ongoing, plans for more

  • New Navigation component simplifies fragment transactions

Activities

#

• Android apps consist of many activities

• Navigating launches an activity

• Use single activities when possible

  • One per entry point

• Richer, more continuous use experience

• Fragments are not necessary, but can help

  • Navigation component, too

Architecture

#

• No recommendation for architecture before

  • Handling Android Lifecycle

Lifecycle

#

• AAC: Lifecyle

  • Fragment implements LifecycleOwner

  • AppCompatActivity implements LifecycleOwner

  • Activity and Lifecycle-Dependent-Thing now gets seprated

Views and Data

#

• Activity had too much stuff

  • Views

  • Data for Views

  • Lifecycle tracking

  • Data change tracking

Live Data and ViewModel

#

• Activity now only contains Views and reference for ViewModel

• Activity observes LiveData

Data

#

• Do it your own! => Room

Room

#

• Local data persistence via SQLite

• Compile-time validation

• LiveData integration

Idea from Repository Pattern

#

Activity/Fragment
↓
ViewModel(contains LiveData)
↓
Repository
-> Model(Room) -> SQLite
-> Remote Data(Retrofit) -> WebService```

### Data Paging

- Paging Library 1.0

  - Works with RecyclerView

  - Fine-grained item changes, bindings

  - Uses background threads

  - Flexible data fetching options

  - Integration with Room

  - Boring name

## Graphics

- OpenGL ES 1.0 => OpenGL ES 3.1/3.2, Vulkan

- Software rendering => Hardware accelerated rendering

- Nine patches => Vector Drawables

- TextureView vs SurfaceView => Use SurfaceView, not TextureView

- Managing bitmaps by hand => Recommended Libraries: Glide, Picasso, Lottie

## Final Thoughts

- Profile your code => Profile your code

- Avoid work when possible

- Minimize memory consumption

- Devices are still resource-constrained

- Battery life is critical

- Bandwidth is precious

- User experience matters

## 所感、個人的に特に印象に残ったことなど

- 可能であれば1 Activityに極力しよう、というのを公式として今回方針を明言しているのは大きいなと感じました

- Java APIの作りもKotlinを意識した形にする、というのは最高そうですね！

- Navigation Component、AAC LifecycleによってFragmentも扱いやすくなった、というようなわりとFragmentが肯定される内容だったのかなと

- サードーパーティー製のライブラリも良いものは使っていこう(Retrofit, Glide, Picassoなどが本動画には登場しています)という姿勢も、全て結果的には良いUXを提供しようというところにつながっていて、説得力というか納得感もあり実際それによって開発者も悩み少なく良いアプリを作れる、というWin-Winな形があるなぁと感じました

以上です！