Android @ Google I/O 2018

At the Google I/O 2018 there were various Android related launches, talks and discussions. Here is one attempt to bring all of the updates under one page for fellow Android Developers to refer and learn.

Contents

• Android Jetpack 🆕
• AppCompat / Support Library / AndroidX 📦
• AndroidKTX 🆕
• Architecture components 📦
  • LifecycleOwner
  • Data Binding
  • Room
• Navigation 🆕
• Paging 🆕
• WorkManager 🆕
• Slices 🆕
• App Bundle 🆕
• Android Design Tools 📦
  • Layout Editor
  • Tools Attributes
  • Sample Data
  • ConstraintLayout
• Android Development Tools 📦
• Android Things 📦

Android Jetpack

Webpage | Videos

A set of libraries, tools and architectural guides to help make it quick and easy to build great Android apps.

• Brings development tools, components, best / recommended practices, recommended app behaviors and common UI elements together under one roof for developer reference and usage.
• Contains 4 major components each of which (and their sub-components) can be used individually.
• Cannot be used as a dependency or a library. Is just an umbrella term for all the libraries maintained by Google to make it easier and faster to develop apps.

Components

• Foundation - Handles Android device fragmentation efficiently and help writing concise, testable code

  • AppCompat / Support Library / AndroidX 📦 - Handle app behavior on older versions of Android efficiently
  • AndroidKTX 🆕 - Android specific extensions to write conciser Kotlin code
  • Multidex - Cross the 65K limit smoothly
  • Test - Test your functions and Android UI easily

• Architecture - Architect your app to follow best and recommended practises from Google

  • Databinding - Cut down on findViewByIds and make data observing / reactive UI elements
  • Lifecycle - Create lifecycle aware components
  • LiveData - A observable stream of data your Activities & Fragments can react to
  • Navigation 🆕 - Define in-app navigation stacks in a single, concise testable file
  • Paging 📦 - Paginate loading data from data sources
  • Room - An SQLite ORM to handle database management in your apps
  • ViewModel - Handle data effectively around lifecycle changes of Android components
  • WorkManager 🆕 - Run parameterized background tasks efficiently

• Behavior - Recommended behaviour for common use cases and tools to achieve them

  • Download Manager - Handle large data downloads
  • Media & Playback - Effectively support media playback and Google cast
  • Notifications - Show notifications across all versions of Android
  • Permissions - Check and request permissions effectively
  • Sharing - Allow users to share to your app and directly to other users on your platform
  • Slices 🆕 - Allow Google Search to launch intents into your app with highlights triggering the user action

• UI - Common UI elements to build effective UIs on different Android versions and platforms

  • Animation & Transitions - Build smooth & transitioning UIs
  • Auto - Build apps for Android Auto with ease
  • Emoji - Add emojis to your app and support older devices effectly
  • Fragment - Break your UI into re-usable components
  • Layout - Build intuitive and performant UIs
  • Palette - Pull useful information from images and play with your UI
  • TV - Build apps for Android TV with ease
  • WearOS by Google - Build apps for WearOS

AppCompat

a.k.a SupportLibrary a.k.a AndroidX

Webpage | Video

• Support libraries will now be called AndroidX (Android Extensions)
• Are going to be a part of Android Jetpack

Changes

• Feature-based artifacts. eg - ViewPager will have its own dependency rather than being bundled with support-v4
• Versioning to be reset from 28.0.0 to 1.0.0
• Strict semantic versioning (Major.Minor.BugFix) i.e. - everything on 1.4 will work on 1.5 till 2.0. Breaking changes only on Major versions
• Per artifact versioning i.e. RecyclerView could be on 1.4 and ViewPager could be on 1.2
• Artifact names to be changed. API specific info like v4, v7 to be dropped and replaced with androidx.<feature>:<feature>-<sub-feature>

Migration

• Automated tool in Android Studio 3.2 Canary 15+

New Releases

• RecyclerView Selection - Allow users to select multiple elements in your RecyclerView. (Like Google Photos)
• RecyclerView ListAdapter - Simpler way to use DiffUtil with animated updates and concurrency support on RecyclerView
• androidx.webkit - Provides access to latest WebView platform APIs
• androidx.browser - Renamed from Chrome custom-tabs.
• HEIF format images support - Coming soon to older versions
• Material Components - Use components following Material Design guidelines easily in your app. Includes:
  • TextFields
  • TextInputs
  • Button
  • BottomAppBar - Actions in app
  • BottomNavigationBar - Sections in app
  • MaterialCardView

AndroidKTX

Webpage | Video | Source code

• An Android specific Kotlin extension library part of Android Jetpack
• Abstracts Android boilerplate code into extension functions making Kotlin code idiomatic, concise and safer
• Reduces the need for multiple confusing Util classes and adds functionality directly to String, ViewGroup, View, Color, Fragments etc
• Contains extensions to elements only in the Android framework
• Has extensions for core framework elements, fragments, palette, collections, lifecycle-reativestreams,sqlite, navigation and work-manager.

Articles

• Exploring KTX for Android - Joe Birch

Architecture Components

Webpage | Video

• 52% Android devs showed interest in using the components
• AppCompatActivity & Fragment implement LifecycleOwner by default now

LifecycleOwner

• When using Fragments and LiveData+ViewModel, change the calls to use the Fragment lifecycle

viewmodel.livedata.observe(viewLifeCycleOwner,Observer{ //viewLifeCycleOwner is the lifecycle of the Fragment
    //Handle new data
})

Data binding

• Pass the LifecycleOwner to your binding initializer to allow bindings to respect Activity lifecycle

  val binding: ViewBinding = DatabindingUtil.getBinding(user)
  binding.setLifecycleOwner(viewLifeCycleOwner)

• Data binding v2 to support incremental compiling and make multi-modular apps build faster
• Supports data binding in Instant Apps

Room

• Room 1.1 has better support for threading
• Due to threading and WriteAheadLogging (WAL) queries to different tables would run in parallel rather than serially
• @RawQuery helps you create queries at run-time allowing you to query columns dynamically.

  @RawQuery
  fun getHouses(query:SimpleSQLiteQuery): List<Houses>

What's next?

• Lifecycle aware tools in Android studio - like NavigationEditor
• Adding templates into Android studio for ViewModel
• More architecture components into Jetpack
• Make other Google APIs "architecture-components-aware"
• Sample apps and Codelabs would be refactored to use architecture components
• Areas under lens:
  • Error Handling
  • Saved State
  • Fragments & Lifecycles
  • Making components Kotlin idiomatic

Navigation

Webpage | Video

Description:

• The Navigation Architecture Component simplifies the implementation of navigation between destinations in your app (A destination is a specific screen in an app)
• By default, the Navigation Architecture Component includes support for Fragments and Activities as destinations, but you can also add support for new types of destinations. A set of destinations compose an app’s “navigation graph.”

Principles:

• Focuses on the Activity being an entry point and container, whereas fragments take the center stage for content and navigation between screens.
• Abstraction layer for navigation, performs Activity transitions, Fragment Transactions and back stack maintenance seamlessly for you.
• Declaring your Navigation graph ahead-of-time so that the system can understand it and execute Navigational code for you.

Requirements:

• Android Studio 3.2 - Canary 14+

Implementation:

• Create a navigation graph (looks like a Wireframe) within XML / Code and link screens with each other (both forward and backward linking if needed)
• Use the NavigationController either
  • Set a view's onClickListener with Navigation.createNavigateOnClickListener(nextScreenId, args) for navigating when clicked
  • At the point of navigation, after business logic, call View.findNavController().navigate(R.id.nextScreenId)

Bonus: Interoperability

• Hooks up with BottomNavigationView, Toolbar and other top-level navigational views for back navigation, selections and automagic transitions when specifying destinations in Menu resource files.
• Hooks up directly with the Manifest Merger so that all Deeplinks / Intent Filters for a given Activity are populated in the Manifest at build time.
• Easier testability of navigational logic since NavigationController can be tested in isolation.

Bonus: Safe Args

• Compile-time checking for Navigation arguments to simplify argument passing between Navigation components.
• Ability to specify argument types and default values if some args are optional.
• Internally creates classes to fetch arguments and exposes them as properties via ClassNameArgs.fromBundle(arguments)

Codelab

• Navigation Codelab

Article

• Exploring Android's Navigation Architecture Component - Nish Tahir

Paging

Webpage | Video

The Paging Library makes it easier for you to load data gradually and gracefully within your app's RecyclerView.

• Allows you to paginate local results with Room database.
• Also allows you to paginate web requests with Retrofit

Code Sample (Non-reactive):

/* In Dao */
@Query("SELECT * FROM users")
fun allUsers(): Datasource.Factory<Int,User>

/* In ViewModel */
init{
    val factory: Datasource.Factory = database.allUsersFactory()
    users = LivePagedListBuilder(factory,30).build() //where 30 is the amount of items to load in one page
}
val users: Live<PagedList<User>> = userDao.allUsers()

/* In Activity / Fragment */
val adapter = MyAdapter()
viewmodel.users.observe(this){
    adapter.submitList(it)
}

/* In Adapter */
class MyAdapter():PagedListAdapter<User, UserViewHolder>(
    object: DiffUtil.ItemCallback<User>(){
        //Override areItemsTheSame and areContentsTheSame
}
){
    override fun onBindViewHolder(holder: UserViewHolder, position: Int){
        val user : User? = getItem(position) //User is now nullable
    }   
}

• PagedList.Config can be used to override the page-size ( amount of items to load in one page), initial load size (amount of items to load on the first page), prefetch distance (prefetch distance which defines how far ahead to load) and enable place holders(display null placeholders)
• Placeholders when enabled, send nulls to the adapter when data is yet to be successfully pulled and can be rendered to show loading to the user.

Code Sample (Reactive):

/* In ViewModel */
//Flowable or Observable
val concertList: Flowable<PagedList<Concert>> = RxPagedListBuilder(
        concertDao.concertsByDate(),
        /* page size */ 50
).buildFlowable(BackpressureStrategy.LATEST)

/* In activity or fragment */
viewModel.concertList.subscribe({flowableList -> 
    adapter.submitList(flowableList)
})

Datasources

• PositionalDataSource - To be used when user can directly scroll to a particular position in the yet-to-be-loaded list. eg - Contacts app
• ItemKeyedDataSource - To be used when your data source holds some kind of ordered key which can help identify the next or previous item to a particular item.
• PageKeyedDataSource - To be used when the data returned to be from the server is paginated as pages and the last element of each page points to the next page.

Network Pagination

• Consider your local cache (database) as the source of truth.
• Whenever you run out of data locally or optionally on first load, ping the server, handle results and insert to database, which in-turn updates the UI.
• Use BoundaryCallback to auto trigger network load when the local runs out of data

Codelab

• Android Paging Codelab

Samples

• googlesamples/android-architecture-components/PagingSample/
• googlesamples/android-architecture-components/PagingWithNetworkSample/

WorkManager

Webpage | Video

The WorkManager API makes it easy to specify deferrable, asynchronous tasks and when they should run

• The jobs will be guaranteed to run in the range as well constraints specified.
• Works in coordination with Doze mode.
• Does not require Google Play Services
• Can chain jobs to run sequentially based on previous results or parallely.
• doWork() (responsible for performing the intended request) by-default runs on the background thread.
• Work can be:
  • OneTimeWorkRequest - Request for non-repeating work.
  • PeriodicWorkRequest - Request for repeating work.
• Constraints can be around - Network, Battery, Idle and Storage on device
• Can observe the status of the work request as a LiveData of WorkStatus
• In chaining, output of one or more jobs can become the input of another.
• A job can be cancelled by calling the cancelWorkById(id)
• A job can be attached a tag to make debugging easier using addTag() on WorkRequest.
• Tags can also be used cancel all the requests belonging to a particular tag.
• Periodic work can be scheduled only after 15 mins
• Periodic work cannot be chained.
• Under the hood delegates and uses
  • JobScheduler (API 23+)
  • Firebase JobDispatcher (if app includes Firebase JobDispatcher)
  • AlarmManager + Broadcast Receivers
• Provides a TestDriver to test the work and run synchronously
• Currently in 1.0.0-alpha01
• Has an additional Kotlin extensions library for Kotlin users

Articles

• Exploring Jetpack: Scheduling tasks with Work Manager - Keval Patel
• Exploring Jetpack: The power of chains in the WorkManager APIs - Keval Patel

Codelab

• Background Work with WorkManager

Slices

Webpage | Video

App Bundle

Webpage | Video

• An Android App Bundle is a new upload format that includes all your app’s compiled code and resources, but defers APK generation and signing to Google Play.
• It uses Google Play’s new app serving model, called Dynamic Delivery. It will generate apk based on the user's device configuration such as screen density, CPU architecture, locale etc. Your user downloads only resources required for his/her device.
• There will be three apks:
  • Base APK: This APK contains code and resources that all other split APKs can access and provides the basic functionality of your app.
  • Configuration APKs: It includes resources for different screen density, CPU architecture, locale etc.
  • Dynamic feature APKs: These are the APKs that are not required at the install time but it will be downloaded and installed in real-time when the feature is required.

Requirements:

• Android Studio 3.2 - Canary 14+. Android Studio 3.2 provides an option to configure your project for Dynamic Delivery while generating signed apk.
• In order to use App Bundle feature, you must enroll in the App Signing on Google Play console.

Codelab

• Your First Android App Bundle

Android Design Tools

Video

Layout Editor

• Convert View - Easily convert an existing ViewGroup into a ConstraintLayout or LinearLayout or CoordinatorLayout by right clicking on it in the Layout Editor.
• Navigate to included layout - If you have an included layout, clicking on it in the editor will open its hierarchy there itself, instead of having to open it separately.

Tools Attributes

Additional information to Android Studio to display test content, apply test parameters during development. All parameters are ignored during run time. Ex:

• tools:listitem : populate item's layout in a RecyclerView in the editor
• tools:itemCount : populate X number of item's in a RecyclerView in the editor
• tools:showIn : to show an included layout as it appears in the parent
• tools:text : set a probable text to a TextView
• tools:textColor - set a probable color to a TextView

Sample Data

Introduced in AS 3.0. It helps you populate data which is not available at the same time. Each time a random value is picked from the sample space.

• Creation - Right click on module > New > Sample Data Directory > Right Click on newly created sampledata directory > New > File > {filename}
• Types supported are: Colors, Strings, Dimensions, Images & Json
• Predefined Sample data:
  • Names: @tools:sample/first_name
  • Cities: @tools:sample/us_cities
  • Lorem Ipsum: @tools:sample/lorem
  • Lorem Ipsum(x words): @tools:sample/lorem[x]
  • Avatars: @tools:sample/avatars
• Can select Sample Data resources from the Resource Picker in AS
• In AS 3.2 you will be able to override random selection and set one resource to be picked each time.

ConstraintLayout

Webpage

ConstraintLayout allows you to create large and complex layouts with a flat view hierarchy (no nested view groups). Sometimes referred to as a RelativeLayout on Steroids.

• ConstraintLayout 1.0 allowed:
  • Relative Positioning
  • Center and Bias Positioning
  • Group behavior (chains / weights)
  • Visibility behavior
  • Aspect Ratio
  • ConstraintSet
  • Guidelines
• ConstraintLayout 1.1 added, in addition to others, Barriers - position an element relative to a set of elements.
• ConstraintLayout 2.0 additions:
  • Helpers - Elements that help you define constraints and design UIs but are not rendered on the screen at runtime. Ex - Guidelines. Categorized as:
    • LayoutManipulation - help you build layouts
    • Post-Layout Manipulation - fly in an element at first launch
    • Rendering and decorating
  • Layers
  • Circular Reveal - Reveal the referenced layout elements in a circular fashion.
  • Decorators - A put animations on your views. Like a Lava Decoration to reveal elements as blobs. Ex:
    • Lava
    • Bottom bar
  • Constraint State - A separate XML file to define various states in which your constraints can animate.
  • MotionLayout - A sub-class of ConstraintLayout to support smoother transitions

Articles

• Android Tools attributes: listItem & sample data rocks! - Thibault de Lambilly

Videos

• ConstraintLayout 2.0 sneak peek - Nicolas Roard & John Hoford

Codelab

• Use ConstraintLayout to design your Android views

Android Development Tools

Video

Android Studio 3.1

• D8 with Desugar integrated lead to 16% increase in build speed on Android Studio 3.1.0
• SQL code editing to allow code completion and project navigation on your SQL queries for Room and vanilla SQLite.
• Kotlin Lint checks in the IDE and console
• C++ CPU profiler to analyse performance impact of C++ code.
• Network Threading Profiler to help analyse each thread in multi-threaded network calls.
• Emulator quick boot launches the emulator in under 3 seconds

Android Studio 3.2

• Supports Android P developer preview APIs
• Supports Android App Bundle
• What's New Window to inboard with new features, changes, etc.
• Generate Signed APK now has new option to generate App Bundle
• Apk analyser works on App Bundle files
• Supports creation of Dynamic modules in the new module creation wizard
• Profilers now breaks performance analysis into sessions to allow comparing of sessions
• CPU profiler can be triggered from code using

  Debug.startMethodTracking()

• Network profiler shows threads, requests and responses
• Memory profiler shows JNI references.
• The new Energy profiler helps monitor battery life
• Emulator saves snapshots to load back into same states
  • Screen Recording added
• Adds Google Sceneform tool to support building of AR apps
  • Also allows previewing 3D models inside AS
• Jetpack refactoring tools allows auto-migration to Android X in gradle and XML files
• Supports Navigation Editor
• Supports Sample Data wizards
• Support will be added for ConstraintLayout motion in the future
• Runs on Pixel Chromebook
  • No ADB yet
• D8 is the default dexer and R8 is the new optimizer and shrinker to improve build speeds as well as replace Proguard

Android Things 🚥

Android Things is Google's platform to support the development of Internet of Things devices. Which is now in 1.0 production ready version. This section has all Android Things related video what's new, updates and best practices

Website | Playlist | Android Things Console

• What's New ? : Learn more about the breadth of hardware reference designs, the operating system, building apps, device management, and support from chip vendors.

• Device Provisioning and Authentication : This talk will discuss how to support authentication, provisioning from a mobile device, and device attestation.

• Android Things Console: Android Things provides a powerful developer Console that manages your device deployments. Learn more about how to take your APKs and hardware configurations, and build them into system images, which can then be rolled out to all of your devices via over-the-air updates.

• System On Modules: How to create your own SOM carrier boards, including creating the design from scratch, working with a fabrication company, assembly and testing, and taking it all the way to production.

• Build Real Consumer Devices : This talk will walk through the journey of building consumer devices like Smart Displays using Android Things

• Build effective OEM-level apps : As an Android Things OEM. How should you structure your code? Should you use activities or services? Should the code be running in the foreground or the background? Do you package all the code into one APK, or split components up into modules? Find answers to all of these questions and more with best practices for building OEM-level apps.

Contribution

Looking for a lot of contributions! Kindly refer the Contribution guidelines for smoother contributions.