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ANDROID APPLICATIONS DEVELOPMENT: A QUICK START GUIDE

Sergii ZhukAndroid Developer at DAXX BV

Kyiv, Bibliotech Talks, 2015-04-28

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Agenda

• Android platform

• How to start

• User Interface

• Basic Android patterns

• How to distribute your app

• Career of Android Developer

• Useful links, books, communities

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Android OS• Linux but user doesn’t have root rights by default

• Open Source Project

• Each device manufacturer modifies OS for his needs, source code is not available in general

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Application execution

Efficient Android Threading by Anders Goransson, O'Reilly Media, Inc., 2014

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Android OS Distribution – 04-2015

https://developer.android.com/about/dashboards/index.html

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Android: not only smartphones

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Android: not only smartphones

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Android: not only smartphones

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Native vs Hybrid Mobile apps

http://www.addthis.com/blog/2014/10/27/7-things-to-consider-when-making-ios-and-android-apps-with-cordova-or-phonegap/

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Android native apps development

• Java: to be executed using Dalvik or ART VMs

• С/С++: Native Development Kit – to develop high-performance modules, will be also launched using VMs

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So, let’s start!

• JDK

• Android SDK

• IDE (Eclipse, IntelliJIDEA, Android Studio)

• Gradle build system (optional)

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HelloWorld (1)

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HelloWorld (2)

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HelloWorld (3)

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Launch your app

• Emulator supplied with Android SDK

• Genymotion emulator (based on Oracle VirtualBox)

• On your smartphone

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AndroidManifest.xml

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Manifest file - AndroidManifest.xml• Permissions (Internet access, storage, …)

• Min and target API version

• Special hardware requests (Camera, Bluetooth, …)

• Some custom Google tools (Play Services, Google Maps)

• Definition of Activities and Services

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Permissions:all or nothing

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Application resources

• Images, Strings, layouts

• Separately from application source code

• Unique integer ID will be generated for each resource name which could be used as a constant

• You can supply alternative resource with the same name to specific folders indicating screen size, locale, screen rotation etc

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Multiple screens support (1)

• Density-independent pixel (dp) – virtual pixel

• “wrap_content” and “match_parent” special values for flexibility

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Multiple screens support (2)

• MDPI

• HDPI

• XHDPI

• XXHDPI

http://developer.android.com/guide/practices/screens_support.html

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Resources example

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Multiple screens support (3)

Density Device Screen resolutionMDPI Galaxy Tab 3 1280*800

HDPI HTC Desire 480*800

XHDPI Nexus 7 1200*1920

XXHDPI Nexus 5 1080*1920

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UI building blocks

• ViewGroup – abstract container for Views to show them using special rules• View – abstract widget like TextView, EditText, Checkbox

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Layout example<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_margin="16dp" android:gravity="center_horizontal" android:orientation="vertical"> <TextView android:id="@+id/text" android:layout_width="120dp" android:layout_height="wrap_content" android:layout_marginBottom="10dp" android:text="I am a TextView"/> <Button android:id="@+id/button" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="I am a Button"/></LinearLayout>

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Layout example

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Common ViewGroups

Horizontal or vertical row, easy to stretch

Position of each element could be configured depending on parent and/or neighbors

Linear Layout Relative Layout

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Common layouts – adapter-based

List View Grid View

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Adapter

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Activity

• Provides a screen with which user can interact to do something

• At least one activity per application

• Notified of screen navigation/device state change through lifecycle callback methods

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Activity stack

Efficient Android Threading by Anders Goransson, O'Reilly Media, Inc., 2014

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Activity workflow

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Service

• Used for long-running operations in the background and does not provide a user interface

• Runs on the main thread of hosting process, could be configured to use a separate thread

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Save application data

• SharedPreferences (key/value pairs)

• Files (internal/external storage)

• SQLite database

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SQLite in Android• Implements most of the SQL-92 standard for

SQL

• All data for the app is stored in one file (if wasn’t configured separately)

• Cross-platform – also used in iOS and Blackberry

http://www.grokkingandroid.com/sqlite-in-android/

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• Serverless, always installed in the system

• By default doesn’t use encryption

• By default is stored in the app folder, could be opened by external tools on rooted devices:

/data/data/<package-name>/databases

SQLite in Android

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External database access

http://independent.academia.edu/parthiban6

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SQLite Android data types

Type Meaning

INTEGERAny number which is not a floating point number

REALFloating-point numbers (8-Byte IEEE 754 – i.e. double precision)

TEXTAny String and also single characters (UTF-8, UTF-16BE or UTF-16LE)

BLOBA binary blob of data

http://www.grokkingandroid.com/sqlite-in-android/

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Content provider

• Presents data to external applications as one or more tables like in a relational database

• System-provided Content providers examples: Contacts, list of music tracks, list of gallery images

• Thread safe

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Broadcast receiver

• Allows to register for system or application events

• Operates with Intent which is a lightweight messaging object

• Could be Asynchronous - all receivers of the broadcast are run in an undefined order, often at the same time or Ordered

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System broadcast messages example

Event Description

Intent.ACTION_BOOT_COMPLETED Boot completed

Intent.ACTION_POWER_CONNECTED Power got connected to the device

Intent.ACTION_POWER_DISCONNECTED Power got disconnected to the device

Intent.ACTION_BATTERY_LOW Triggered on low battery. Typically used to reduce activities in your app which consume power

Intent.ACTION_PHONE_STATE_CHANGED The call state (cellular) on the device has changed

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Use Case: Interaction with backend

• Synchronous HTTP request in the separate thread- OR use external library (Retrofit, Volley, Enroscar)

• Parse result (for json - GSON is de-facto standard)

• Post result to the UI

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Use Case: Facebook integration

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Use Case: geolocation

• GPS, Cell-ID, Wi-Fi. Need to declare permissions at AndroidManifest.xml

• “Cold start”: wait for GPS

• Callback on device being moved

• Rapid battery drain problem

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Automated application testing• No?

• Espresso and JUnit - uses emulator or real device– Slow

• Robolectric: texts executed inside your desktop PC JVM

• Blackbox UI testing (Robotium)

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How to build your app

• In IDE

• Old school: Ant, Maven

• Gradle

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Gradle

• Good IDE integration

• Dependency management (Maven, Ivy) out of the box

• Sign applications configuration out of the box

• Backward compatibility breaks quite often on new Gradle version update

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Gradle script: shortened exampleandroid { compileSdkVersion 15 buildToolsVersion "22.0.1"

defaultConfig { applicationId "org.sergez.myapplication.app" minSdkVersion 9 targetSdkVersion 22 versionCode 1 versionName "1.0" } compileOptions { sourceCompatibility JavaVersion.VERSION_1_6 targetCompatibility JavaVersion.VERSION_1_6 } buildTypes { release { minifyEnabled false proguardFiles getDefaultProguardFile('proguard.txt'), 'p-r.pro' } }}dependencies { compile 'com.android.support:support-v4:22.0.0' compile 'com.android.support:appcompat-v7:22.+' compile fileTree(dir: 'libs', include: ['*.jar'])}

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Where to publish your app

• Google Play Store

• Samsung Apps

• Amazon Appstore for Android

• Asian application stores

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Google Play Store (1)

• $25 for Developer Account with publishing rights

• Application is available in Play Store in 3-6 hours after being published

• Auto-moderation in general, manual post-moderation could be applied in some cases

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Google Play Store (2)

• Allows to publish app in alpha- and beta test modes

• Customization of app visibility for different countries and devices

• User could rate the app and leave a feedback, developer could respond to this feedback

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Monetizing your app: Play Store

• Paid apps– Play Store takes 30%– Android users don’t like to pay

• Ads

• Donations

• Freemium

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Keep in mind when starting a new project

• Android target version

• Special UI design for tablets

• Availability of mockups and flow explanation

• Amount of non-standard UI elements

• UI will be outdated in 0.5-2 years

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Get a job: where and how?

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• Freelance

• Android app as only a small part of a big product

• Mobile development company (outsourcing)

• Mobile-first product

Get a job: where and how?

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Useful resources

• https://developer.android.com

• http://android-developers.blogspot.com/

• E-book «The Busy Coder's Guide to Android Development»

• Android Performance Patterns – YouTube and G+

• DOU.ua Android Digest

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Useful resources

• Udacity “UD853 - Developing Android Apps”

• Coursera “Mobile Cloud Computing with Android”

• Lynda, Udemy, Stanford Online

• AppTractor Podcast (in Russian)

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Thanks!

Contact me:sergey.public@gmail.comhttp://ua.linkedin.com/in/sergiizhukhttp://fb.com/sergii.zhuk