Google I/O 2018: Android Notes

Highlights

  1. All android support library code is moving to androidx namespace. No more android.support.v4 or android.support.v7 namespaces.
  2. Android app bundle to split the app into downloadable modules
  3. Navigation library to set up navigation between different activities/fragments.
  4. Use WorkMananger for background work – this is an improvement to JobScheduler
  5. Major improvements to Android Studio. Most standalone tools deprecated in favor of adding the same functionality into Android Studio.
  6. Major improvements to Android Vitals which in Google Play to learn more about what’s going on with Android app’s performance.
  7. Android P does more profiling to improve code locality for faster execution.

Modern Android Development

  1. hierarchy viewer replaced by ViewTree in Android Studio
  2. TraceView replaced by Systrace in Android Studio
  3. Profiler (DDMS) replaced by Android Profiler in Android Studio
  4. Dalvik replaced by ART
  5. Java replaced by Kotlin as preferred language
  6. Layouts
    1. Absolute Layout – deprecated
    2. Linear Layout – still OK
    3. Frame Layout – still OK
    4. Grid Layout – discouraged
    5. Relative Layout – discouraged
    6. ConstraintLayout – recommended
  7. ListView, GridView, and Gallery are deprecated. RecyclerView is recommended with ListAdapter for updations.
  8. Platform Fragments (android.app.fragments) are deprecated. Support library fragments recommended.
  9. Single activity app recommended
  10. Rather than managing activity lifecycle use Lifecycle to observe state changes
  11. Rather than keeping plain data with views, use LiveData to update views automatically. Use ViewModel to deal with screen rotation.
  12. Room is recommended in place of SQLite
  13. CursorAdapter and AsyncListUtil are discouraged. Use Paging instead with a neat, graceful offline use-case handling trick.
  14. Don’t do manual bitmap management. Use Glide, Picasso, or Lottie instead.
  15. Between TextureView and SurfaceView, use SurfaceView.
  16. Nine-patches are discouraged. Use Vector Drawables.
  17. Use FusedLocationProviderClient for fetching device location. Wi-Fi access triangulation is coming to Android P. FusedLocationProvider will eventually add support for that for indoor location tracking.
  18. MediaPlayer is discouraged, use ExoPlayer instead. A detailed hands-on presentation on ExoPlayer

Performance

  1. 42% 1-star reviews mention crashes/bugs
  2. ANR/crash rate reduces engagement – use StrictMode to catch them early
  3. Avoid IPC on the main thread, StrictMode won’t catch the violation, and you would never know what’s happening on the other side of the IPC call which can block the main thread
  4. If BroadcastReceiver#onReceive is going to take more than 10 seconds, then call goAsync for background processing and call PendingResult#onFinish() once that’s finished
  5. WakeLocks – avoid using them. All except PARTIAL_WAKE_LOCK are deprecated with Android P.
    1. Use FLAG_KEEP_SCREEN_ON for keeping the screen on in an activity
    2. Use WorkMananger for background work
    3. Use AlarmManager for short interval callbacks
  6. enums are not discouraged anymore. Platform code avoids it but unlike in prior Android versions, the penalty for enums is low now.
  7. A good introduction to Android’s display rendering
  8. A good introduction to Android’s text handling
  9. Text handling issues
    1. Only framework spans can be parceled, don’t mix custom spans with framework spans since only the frameworks will be part of the copied text
    2. After ~250 spans or more, SpannableStringBuilder ends up being more performant than SpannableString since the former internally uses trees.
    3. Metrics affecting spans cause measure-layout-draw calls, while appearance affecting spans cause layout-draw calls, therefore, the former is more expensive.
    4. Text measurement takes a lot of time on the UI thread, consider creating PrecomputedText on the background thread.
    5. android:autoLink = true works via RegEx and has bad performance. Consider using Linkify on the background thread. Android P also supports deep learning based TextClassifier which is also invoked on the background thread.
  10. Testing your app for background restriction – adb shell appops set <package name> RUN_ANY_IN_BACKGROUND ignore # applies background restriction (change “ignore” to “allow” to remove restriction)

Next Billion Users

  1. 28% searches in India are voice searches
  2. 2-wheeler mode added to Google Maps
  3. Google Tez uses Ultrasound for pairing and sending money to the nearby receiver
  4. Files Go – Folder based hierarchy won’t work for users who have never had PC before. Therefore, shows photos based on associations like “WhatsApp Images” or “Camera”. Supports P2P file sharing for fast transfers.
  5. Design for next billion users – http://design.google/nbu
  6. Android Go
    1. 25% devices in 2018 shipped with <= 1GB RAM (target for Android Go)
    2. Every 6 MB app size reduces install rate by 1%
    3. India – largest market for Go. The USA – second largest market for Go.
    4. 5 seconds cold start goal
    5. Users opt for smaller apk size with a lower rating.
    6. Average apk size is 30 MB. Go recommends 40MB max app size for non-game and 65MB for game apps.

MLKit

  1. On-device + cloud APIs. On device APIs are free.
  2. Firebase support to download model and even do A/B testing.
  3. Experimental support to convert TensorFlow models to TensorFlow Lite models.

Compiler

  1. D8 – new Dexer, now default. Enable/disable via “android.enableD8 = true/false”
  2. R8 – new optimizer, now default replacing proguard, still opt-in in 3.2. Enable via android.enableR8 = true

Kotlin – talk can be here

  1. Use properties in lieu of default getters/setters
  2. Use data classes to generate equals, hash method etc.
  3. Use default args instead of method overloading
  4. Use top-level functions as well as local functions (function inside functions for better encapsulation
  5.  Use function extensions to make the code more readable, eg. extend String class with isDigit to be able to later write the code like “1234”.isDigit
  6. Use smart casts
  7. Use sealed classes for a superclass which should not be extendable beyond the compile-time
  8. Use string interpolation in println, eg. println(“name is ${name}”)
  9. Use val (read-only values) by default, only use var (read-write variable) when there is a strong reason
  10. Declare lambda functions as inline to remove the cost of having an extra class
  11. Use co-routines via async instead of creating new threads
  12. Use suspend + async to convert callbacks into more readable synchronously written code

Google I/O 2017: Android Notes

Infrastructure – Architecture & Performance

  1. Android Vitals – More visibility in Google Play dev console on battery drain, wakelocks being held for too long, ANRs, crashes, dropped frames, and frozen frames.
  2. Architecture components – better handling of the lifecycle, Room (ORM for Sqlite), live data observers. The API looks clunky though.

Performance

  1. 50% 1-star reviews mention stability & bugs.
  2. 60% 5-star reviews mention speed, design, or reliability.
  3. Apps with > 5% crash rate have 30% higher uninstall rate.

Emerging Markets

  1. > 100M users came online in 2016.
  2. 1B 2G devices expected in 2020.
  3. 50% of India is on 2G
  4. 33% users run out of storage in India every day.
  5. Data is expensive – it costs ~$2 to download a 40MB free app in India
  6. 53% users abandon websites if it takes more than 3 seconds to load

Action items

  1. Remove barriers – app size, always online requirement
  2. Optimize for 2G speeds
  3. Build for intermittent connectivity – offline is not a bug, its a state for the users
  4. Provide better multilingual support
  5. Guide new users – Case study: minimalistic empty chrome screen is unwelcoming in India. Adding links to recent websites and news articles made it more welcoming.

Android Go

Rechristened versions of Android One, to be installed on all devices with less than 1GB RAM going forward. Consists of Lite apps. More visibility into data usage, and easy mobile top-ups.

  1. Youtube Go, and Play Go will support P2P video & file sharing.
  2. Chrome Data saver on by default. Related: “Save-Data” header
  3. 10MB per app download size goal
  4. Multi-lingual GBoard
  5. More severe limits on background
  6. DEX reordering to increase disk locality of the content

Slimming down app size

Installed size consists of download size, followed by unpacking, compilation & optimization phase.
20% downloads are canceled or fail if app size >= 100MB

Action items

  1. minification via proguard
  2. split-density apk , can be automated by Google Play if you are willing to hand them your key
  3. vector drawable (API 14+), this might increase CPU & RAM usage for complex drawable though
  4. Exclude sparse translations
  5. Downloadable fonts
  6. AAPT2 – dead version elimination, resource de-duplication, and smarter image cruncher

Misc

  1. Kotlin officially supported in Android. Recommended talk: Introduction to Kotlin
  2. App overlay not allowed on the system UI anymore
  3. Android Studio Apk Analyzer is proguard-aware
  4. Brotli compression for Google Play app updates
  5. Instant apps

New Features (only in Android O)

  1.  WebView improvements – safe browsing support, multi-process, crashes + low-mem handling
  2. Auto-fill
  3. Fonts as first class resources
  4. Improved Media file access – ability to share big files like videos from one app to another without fully downloading them first.
  5. New Skia Renderer to cut down jank.
  6. Color management for different color spaces. Support for wide color Gamut. I would highly recommend watching Understanding Color talk.
  7. Even more rigorous clamp down on background processes & wake locks usage to save battery
  8. ART – use JIT profiling to relayout dex file reduces RAM & I/O, new concurrent Garbage Collector (using read barrier) to remove GC pauses,  more code inlining, code relocation, class hierarchy analysis to optimistically decide when classes & methods can be assumed final, automated SIMD instruction generation.
  9. App icons – background & foreground layers from the app (with mask from the system)
  10. Notifications  – Separated into 4 chunks – ongoing, people-to-people, general, and BTW. Notifications won’t reorder while you are looking at them. Notification Channels (notification categories which users can block/mute), mandatory for targeting API 26. App icon badging (“dot” in Google’ parlance).

New Features (backported via support library v26)

  1. Support library going API 14+ only. 1% users (~20M by Google’s count) are still on API 10.
  2. Downloadable fonts
  3. EmojiCompat for backward emoji support
  4. Better use of RenderThread to cut down on jank (frame drops)

Demystifying Android rendering: Jank and ANR

Almost everyone developing an Android app has seen something like this in their logs.

On most devices, the Android platform tries to render a new frame every 16 milliseconds (60 fps).   The rendering requires that whatever work is happening on the UI thread should finish in that timeframe (well, actually in less than that). Any unit of work (== Runnable) scheduled on the UI thread has to fit in that. When the work takes longer, then frames are skipped. One skipped frame is 16 ms of the hung screen. The UI looks janky and unresponsive and if the user interacts with the screen and application does not respond in time (5 seconds) then Application Not Responding (ANR) shows up.

Another interesting scenario where the work can take longer is when the work involves acquiring a lock (for example, for executing synchronized code). Any synchronized code on the main thread is almost always a bad idea since you have no control over who could be holding the lock. And the developer writing the code to run on a background thread has no idea that holding a particular lock can cause any problems. Android has two tools to debug this. One of them is dumpsys for the statistical info; the other one is Method profiling via Android Device Monitor for identifying the culprits.

And, by the way, Choreographer is the class which does the actual rendering work.

 

Built-in “Developer options” in Android

Android has a few really good settings built right into the platform for debugging under a hidden “Developer Options” menu. You can turn then on via Settings -> About Phone -> Build Number (tap 7 times). The steps will be similar but might vary a bit across OEMs. In older versions of Android, this used to be an explicit option under the Settings tab.

I find the following options to be useful for the development

  1. Don’t keep activities
    Android can destroy any activity which is not visible in the foreground at all. The destroy is a bit of a misnomer here since activity will be allowed to preserve its state (via saveInstanceState). This option allows you force that on all apps. It is harder to keep this option always on since many badly designed Android apps misbehave and even the good ones have a deteriorated performance due to repeated re-creation. I wish there was a way to force this only on the app under development.
  2. Force RTL layout direction
    to test your app’s look & feel in an RTL language like Hebrew or Urdu. This option is useful since it actually reveals evolving and varied behavior across different versions of Androidrtl_forced
  3. Profile GPU rendering
    Shows a nice cool graph of the load on the UI thread and when your app fails to render a frame in Android recommended 16 milli-seconds timeframe.

    Courtesy XDA

    Courtesy XDA

  4. Stay awake [while charging]
    when you don’t want your screen to turn off while it’s charging [& connected to your laptop for the development]. I wish Google actually provided “Stay awake while USB debugging” option.
  5. Verify apps over USB
    Disable it unless you don’t trust the app you are working on
  6. Pointer Location
    This option draws a set of perpendicular lines at the point of touch, useful to see if a set of views (like buttons, text fields etc.) align or not.
  7. Show Layout bounds
    shows the bounds of all the views, annoying to always keep on but useful for quick testing.
  8. Debug GPU overdraw
    Google recommends it but I have rarely seen any benefits of turning this on since due to animation, overdraw is almost always present.
  9. Running services
    You can check out your app and see if it is listed and is running some spurious service in the background.Running apps

Thoughts on Tizen

Users won’t buy a phone till they know that their basic set of apps are available on the device.
That pretty much rules out players like BlackBerry 10JollaUbuntu OS and Firefox OS.
Even Microsoft is still struggling.
OEMs like Samsung, HTC, LG, Sony have been hit hard by commoditization of Android. Google makes money from Google Play, cheaper phones imply more users. So, commoditization of Android OEMs is good for Google.
These OEMs have to customize Android as per Google’s requirements which have increased over time.
They cannot manufacture a competing version of Android (like Amazon’s Fire Phone) either.
This leaves us with iOS and Google-experience Android duopoly.
The only way to break that duopoly is Samsung, which is big enough that it can convince major developers to develop apps for its devices and throw money at marketing to reach out to end users.
It can make money from selling devices as well as selling apps (via app store).
A completely open source OS can pull open source developers from GNU/Linux and Android to develop it.
A completely open source OS can convince other OEMs to use it and in lieu, they can partner with Samsung on app store revenue sharing.
It remains to see what Tizen’s delayed launch eventually leads to but its a matter of survival for Samsung.

 

Android command-line: gradle and testing

For android projects, some engineers use Android Studio (new), some use Eclipse with ADT (old), few like me still savor command line, this blog post is about handling (building, installing and testing) android projects from command line.

  1. To create android project
  2. After changing to directory test_android_app (cd test_android_app), fix a bug

     
  3. Some useful gradle commands
  4. The code will be in src directory, eg. for the Main activity, code is in src/main/java/net/ashishb/TestAndroidApp/Main.java and test is in src/androidTest/java/net/ashishb/TestAndroidApp/MainTest.java
  5. For testing, modify the Main class and add square method,

    And in MainTest
  6. Modify build.gradle to add a testing config

     
  7. Run the test(s)
  8. Complete code can be seen at https://github.com/ashishb/android_gradle_demo

How to start locale settings activity on android from command-line

A useful and handy command specially when you during experimentation, you are stuck because of a changing language settings to an undecipherable foreign language.

Android, Gradle and compile-time only dependencies

Android plugin for Gradle does not support Java-style compile time only dependencies.

After spending a few hours on trying to build android app targeted for Amazon SDK (without using Amazon’s Android specific plugin but just their jar stubs for maps, ADM and Home widget), I finally found that the one way to support compile-time dependencies is following.

For application project

For the library project

References

  1. https://stackoverflow.com/questions/16613722/gradle-configurations-not-working-as-expected-in-new-android-build-system
  2. http://stackoverflow.com/a/24157721

How to compile android emulator on ubuntu 13.10

I was trying to make some modifications to android emulator and was unable to find good set of instructions for the compiling the same.

Here are mine.

Why Nokia’s (rumored) Android phone is doomed

In Feb 2014, WSJ is reporting that Nokia is working on an Android phone.
In Sept 2010,

Anssi Vanjoki, outgoing head of Nokia’s smartphone division, likens mobile phone makers that adopt Google’s software to Finnish boys who “pee in their pants” for warmth in the winter. Temporary relief is followed by an even worse predicament.  [source]

As someone who has advocated Android for Nokia in the past, I think its just too late now to do that.

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