lecture android best practices

Android Development Best Practices. Android Wearby Yuriy Voznyak, Software Engineer

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You can view the presentation on

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Android Wear

OS for SmartWatches and wearable devices

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How to pair with?● Install the Android Wear

app● Tap “Pair with a new

watch”● Tap “Enable

Notifications”

Some Wear devices can be paired with iOS

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What systems have in common?Android Wear and Android have common API. Except:

● No WebView in Wear;● No direct internet connection: use Data Layer

API instead;● No print subsystem;● No cloud backup subsystem;● No application widgets (e.g. on Launchers);● No interaction with USB devices.

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How to Show NotificationsDo nothing :) all Push Notifications appear on Wear. Or customize notifications with Wear extensions:

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● User can interact with Wear notifications via Pending Intent;

● Notifications on Wear can be customized;● Show only wearable notification, not on

handheld;● Set custom backgrounds.

Distributing Wear appsWhen publishing to users, you must package a wearable app inside of a handheld app, because users cannot browse and install apps directly on the wearable. If packaged properly, when users download the handheld app, the system automatically pushes the wearable app to the paired wearable.

While developing, installing apps with adb install or Android Studio directly to the wearable is required.

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Defining LayoutsSpecify Different Layouts for Square and Round Screens

<android.support.wearable.view.WatchViewStubxmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:id="@+id/watch_view_stub"android:layout_width="match_parent"android:layout_height="match_parent"

app:rectLayout="@layout/rect_activity_wear"app:roundLayout="@layout/round_activity_wear">

</android.support.wearable.view.WatchViewStub> 7

Accessing layout viewsThe layouts that you specify for square or round screens are not inflated until WatchViewStub detects the shape of the screen, so your app cannot access their views immediately. To access these views, set a listener in your activity to be notified when the shape-specific layout has been inflated:

@Overrideprotected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_wear); WatchViewStub stub = (WatchViewStub) findViewById(R.id.watch_view_stub); stub.setOnLayoutInflatedListener(new WatchViewStub.OnLayoutInflatedListener() { @Override public void onLayoutInflated(WatchViewStub stub) { TextView tv = (TextView) stub.findViewById(R.id.text); // Now you can access views ... } });}

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Also You Can

● Design new Watch Faces;● Work with built-in speakers into

Wearables;● Debug over Bluetooth;● Send and collect data via Sync

mechanism;● … And much much more.

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Best Practices: Useful Libraries

● Gson;● EventBus;● ButterKnife● Dagger 2● Glide ● DBFlow

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GSONGson is a Java library used for serializing and deserializing Java objects from and into JSON. A task you will frequently need to do if you communicate with APIs. JSON is recommended to use because it’s lightweight and much simpler than XML.

// SerializeString userJSON = new Gson().toJson(user);

// DeserializeUser user = new Gson().fromJson(userJSON, User.class);

Gson works great with Retrofit as serializer/deserializer.

See more on https://github.com/google/gson11

EventBus EventBus is a library that simplifies communication between different parts of your application. For example, sending something from an Activity to a running Service, or easy interaction between fragments.

EventBus is an Android optimized publish/subscribe event bus. A typical use case for Android apps is gluing Activities, Fragments, and background threads together. Conventional wiring of those elements often introduces complex and error-prone dependencies and life cycle issues. With EventBus propagating listeners through all participants (e.g. background service -> activity -> multiple fragments or helper classes) becomes deprecated. EventBus decouples event senders and receivers and thus simplifies communication between app components. Less code, better quality. And you don't need to implement a single interface! 12

EventBus Examplepublic class HomeActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); EventBus.getDefault().register(this); // register EventBus } @Override protected void onDestroy() { super.onDestroy(); EventBus.getDefault().unregister(this); // unregister EventBus } public void onEventMainThread(NetworkStateChanged event) { if (!event.isInternetConnected()) { Toast.makeText(this, "No Internet connection!", Toast.LENGTH_SHORT).show(); } }}

public class NetworkStateChanged {}

EventBus.getDefault().post(new NetworkStateChanged());

See more on http://greenrobot.org/eventbus/ 13

ButterknifeA library for binding Android views to fields and methods (for instance, binding a view OnClick to a method). Annotate fields with @Bind and a view ID for Butter Knife to find and automatically cast the corresponding view in your layout.

class ExampleActivity extends Activity { @BindView(R.id.title) TextView title; @BindView(R.id.subtitle) TextView subtitle; @BindView(R.id.footer) TextView footer;

@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.simple_activity); ButterKnife.bind(this); // TODO Use fields... }}

See more on http://jakewharton.github.io/butterknife/ 14

Dagger 2

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Dagger is a fully static, compile-time dependency injection framework for both Java and Android. It is an adaptation of an earlier version created by Square and now maintained by Google. Dagger creates instances of your classes and satisfies their dependencies. It relies on javax.inject.Inject annotation to identify which constructors or fields should be treated as dependencies.

Dagger 2 is the successor of the famous Dagger dependency injection library. One of the major improvements is using zero reflection in generated injection code, which makes debugging a lot easier.

Dagger 2 is the first to implement the full stack with generated code. The guiding principle is to generate code that mimics the code that a user might have hand-written to ensure that dependency injection is as simple, traceable and performant as it can be.

Dagger Code Exampleclass Thermosiphon implements Pump { private final Heater heater;

@Inject Thermosiphon(Heater heater) { this.heater = heater; } ...}

class CoffeeMaker { @Inject Heater heater; @Inject Pump pump;

...}

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Also allows to resolve dependencies; Build the dependencies Graph; Resolve constructors as Singletons; Lazy Injections; Compile-time validation and much much more.

Read more on http://google.github.io/dagger/

GlideGlide is the library to use for loading images. Current alternatives are Universal Image Loader and Picasso.

Glide is recommended by Google.

Here's a simple example how you can use Glide to load an image from a URL into ImageView:

ImageView imageView = (ImageView) findViewById(R.id.my_image_view);

Glide.with(this).load("http://goo.gl/gEgYUd").into(imageView);

See more on https://github.com/bumptech/glide/wiki17

DBFlowThe Fastest Android ORM Database Library

DBFlow uses Annotation Processing functionality to generate all sorts of classes and interactions with the database at compile time. This enables the library to run at native speed and becomes as fast as writing the code yourself. Also, generating code is transparent–we can see the code that the app executes and catch errors at compile time. Reflection is difficult to debug, since we will only catch errors at runtime.

List devices = new Select().from(DeviceObject.class) .where( Condition.column(DeviceObject$Table.NAME).is("Samsung-Galaxy-S5"), Condition.column(DeviceObject$Table.CARRIER).is("T-Mobile")).queryList();

Delete.table(DeviceObject.class);

See more on https://github.com/Raizlabs/DBFlow 18

It is only small amount

Think about using libraries!

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Gradle

● Build different flavours or variants of your app● Make simple script-like tasks● Manage and download dependencies● Customize keystores● And more

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Maven Dependencies for GradleThe main reason is not to keep the library locally as Jar or something elseapply plugin: 'com.android.application'

repositories { mavenCentral()}

dependencies { compile group: 'org.hibernate', name: 'hibernate-core', version: '3.6.7.Final' testCompile group: 'junit', name: 'junit', version: '4.+'}

Or

dependencies { compile 'org.hibernate:hibernate-core:3.6.7.Final'}

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IDE

Use Android Studio

Eclipse is deprecated since 2015

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Components and UI

● Avoid using nested layouts; Avoid deep hierarchy for views

● Use styles instead of views spot customization;● Don`t put much code to Activities or Fragments;● Dont`use Intents for in-application

communication. Use RxJava or EventBus if possible;

● Don`t rely on Android System-level intents.23

ProGuardProGuard is a tool for code obfuscation, shrinking and optimization

● Use it;● Verify Release builds for ProGuard rules;● Keep mapping.txt for every release.

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Naming Convention

Naming Convention Must Be!

Bad naming convention is better than no convention

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Useful Links

● https://github.com/futurice/android-best-practices● https://developer.android.com/guide/practices/index.html● https://developer.android.com/training/best-performance.html● https://developer.android.com/training/best-ui.html● http://www.innofied.com/13-android-development-best-practic

es/● https://github.com/ribot/android-guidelines/blob/master/project

_and_code_guidelines.md● https://google.com

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