Android development first steps

Christoforos Nalmpantis Software Engineer and Tech

Entrepreneur Co-Founder of Neighbourfood

Founder of Coeus Labs

Loyds Banking Group

Powa Technologies

BusuuWhat Now Travel

The App Business

Agenda

• Working as an Android Engineer in London

• What is Android

• Think "mobile"

• Tools in Android Development

• Android Development lifecycle

• Basic components

• Acitivity lifecycle - demo

• My first app

Working as an Android Engineer in London

• Opportunities

• Big tech companies: Google, Amazon, Facebook, Yahoo, (Apple?) etc

• Start ups (SwiftKey, CityMapper, Busuu)

• Finance, Games, Enterprise etc

• Interview process: Algorithms, Data structures, Design patterns, Android framework, Java

• Salary expectations 25k - 90k (£1,673 - £4,960)

• Big events, conferences, many meetups, interesting people, startup spirit

Android History

• Android, Inc. was founded in Palo Alto, California in October 2003, by Andy Rubin, Rich Miner, Nick Sears and Chris White.

• Android was intended for digital cameras.

• Google acquired Android Inc. on August 17, 2005.

• At Google, the team led by Rubin developed a mobile device platform powered by the Linux kernel.

Android is a software stack

• Linux Kernel - low level tasks

• Libraries in C C++ (e.g. sqlite) and Android runtime (e.g. Android virtual machines, Dalvik and more recently ART.

• Application Framework - Your apps run within its own instance of the VM using the classes and services provided here.

• Applications - Includes your app and all apps installed on the device.

Lollipop

• Material design: fluid, purposeful motion

• Notifications: respond directly from your lock screen.

• Battery: feature that extends your device by up to 90 minutes

• More ways to secure your device: multiple user accounts, guest mode, android smart lock.

• Even more devices: phones, tablets, wear, tv, auto, one.

https://www.youtube.com/watch?v=d36cIFCJvQs

Start thinking like a mobile developer.

• Object Oriented Programming (OOP)

• Java

• Smartphones = small computers

• User Experience (UX) is very important.

• Mobile OS is an ecosystem of many Apps

Key mobile challenges

• Low processing power

• Limited RAM

• Intermittent, low bandwidth, high latency data connections

• Impact on battery

• (Android?) Fragmentation

• Support multiple devices

Android version history

Tablets

Android Beam

HCE

FroyoGingerbreadIce Cream SandwichJelly BeanKit KatLollipop

0

10

20

30

40

Region 1

FroyoGingerbreadIce Cream SandwichJelly BeanKit KatLollipop

What happens when you run an app in Android Studio?

Android Project Build Resources

Manifest

Byte Code

SignInstall

on device

n

Tools used in Android development.

• Android Studio

• Gradle

• Genymotion

• SDK Tools

• Version control system (git)

• Continuous Integration tools (Jenkins)

Android Studio Intelligent Code Editor

Android Studio Rich Layout Editor

Android Studio Multiscreen App Development

Android Studio Memory Monitor

Android Studio CPU Monitor

Android Studio Device Log Messages

Gradle

• From command line to Ide to continuous integration

• Declare and execute all tasks necessary to compile, test, package and ship.

• Support multi-language, multi-platform, multi-project and multi-channel software, Saas and mobile apps

Gradle Build Automation System

A faster Android emulator

Genymotion is the next generation of the AndroVM open source project, already trusted by 2,500,000 developers. It’s even easier to use and offers lots more features.

Android SDK Tools

adb

android

AVD Manager

bmgr

Device Monitor

dmtracedump

Draw 9-Patch

Emulator

etc1tool

hprof-conv

jobb

lint

logcatmksdcard

ProGuard SDK Manager

Tracer for OpenGL ES

Traceviewzipalign

Android SDK Tools location of sdk tools

Android SDK Tools Android Device Monitor

Android SDK Tools HierarchyViewer

Continuous Integration Jenkins

Git

• Git is a free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency.

• UI client for git -> SourceTree

• The Gitflow Workflow defines a strict branching model designed around the project release.

Git SourceTree

Android Development Lifecycle Agile Methodology

–Manifesto for Agile Software Development

“Customer Collaboration over Contract negotiation”

“Working Software over Comprehensive Documentation”

“Individuals and Interactions over Processes and tools”

“Responding to change over Following a plan”

Basic Android Components

Activities An Activity represents a single screen with a user interface

ServicesA service is a component that runs in the

background to perform long-running operations or to perform work for remote processes.

Content Providers

A content provider manages a shared set of app data.

Broadcast Receivers

A Broadcast receiver is a component that responds to system-wide broadcast announcements.

The Manifest File

• Android system must know that the component exists by reading the app’s AndroidManifest.xml file.

• Identify any user permissions the app requires.

• Declare the minimum API level required by the app.

• Declare hardware and software features used or required by the app (e.g. camera, bluetooth services).

• Other than Android framework APIs (Google maps library).

• And more.

Basic Android Components AndroidManifest

Views and ViewGroups

• A View is the basic UI component.

• Buttons, TextViews, ImageViews and other are all subclasses of View.

• ViewGroup is also subclass of a View, and can contain many views.

• Layouts are subclasses of ViewGroup ( LinearLayout, RelativeLayout, FrameLayout).

• To convert Layouts to Java objects we need to inflate the layout.

• To use our views in Java we need to find the views after inflating the layout which contains them.

Basic Android Components Views and ViewGroups

Time to code Activity Lifecycle

Time to code Activity Lifecycle

Time to code Activity Lifecycle

Time to code Activity Lifecycle

WTF

Time to code Activity Lifecycle

Declare your activity

Activity Lifecycle

• onCreate(Bundle savedInstanceState)

• onStart()

• onResume()

• Now the activity is visible and the user can interact with it!

Activity Lifecycle

• onPause()

• onStop()

• Now the app is not visible! (these are images not real views)

Activity Lifecycle

• onRestart()

• onStart()

• onResume()

• Now the activity is visible again and the user can interact with it!

Activity Lifecycle

• onPause()

• Now the activity is partial visible! This is a technical term and means that the activity is on Pause() because a dialog is shown. The user cannot interact with the UI of our activity anymore.

Activity Lifecycle

• onResume()

• Now the activity is visible again and the user can interact with it!

Activity lifecycle states

• Entire Lifetime: This is the lifetime between the first call to the onCreate() and the final call to onDestroy() method. We create all global resources such as screen layout, global variables etc in onCreate() and release all resources with onDestroy() call.

• Visible Lifetime: It is the lifetime of an Activity between onStart() and onStop() method calls. In this the Activity is visible to the user and he may or may not be able to interact with it. During the visible lifetime, an Activity maintains its state intact.

• Foreground Lifetime: Foreground lifetime starts with onResume() and ends with onPause() method calls. During this, the Activity is completely visible to the user and is on top of all other Activities so that user can interact with it.

Time to code Activity Lifecycle

My first Android App

• Collect requirements

• Start development process

• Test

• Iterate again until the app is ready for release.

• Maintain the app and add new features using the previous steps.

My first Android App Collect requirements

Break the project into small user stories

• As a user I want an android app.

• As a user I want the app to show images from london.

• As a user I want the images to be shown in a list view.

• As a user I want the listview to support infinite images and scroll smoothly.

• As a user I want to tap on an image and show it in full screen.

Analyse requirements

• Which components do we need?

• 2 screens -> 2 Activities

• 2 screens + 1 imageItem -> 3 Layouts

• List of images -> RecyclerView

• Show data in list -> Adapter

• Items of images -> ViewHolder

• Load images from Internet -> Picasso

START CODING!!!

ScrollView<?xml version="1.0" encoding=“utf-8"?> <ScrollView xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <ImageView android:id="@+id/item_image_imageView" android:layout_width="match_parent" android:layout_height="@dimen/image_size" android:scaleType="centerCrop" /> <ImageView android:layout_width="match_parent" android:layout_height="@dimen/image_size" android:scaleType="centerCrop" /> <ImageView android:layout_width="match_parent" android:layout_height="@dimen/image_size" android:scaleType="centerCrop" /> . . . </LinearLayout> </ScrollView>

If you have 100 images in the list and can fit 3 items on screen at once - what is the minimum number of views you need to create to scroll through the list?

1. one2. three3. four4. five5. ten6. one hundred

ListView

• Request a view for every visible item.

• Create two more for both directions ( up/down) to avoid flickering of the screen as a new view is created and populated.

• As you scroll more views are added to memory

RecyclerView

• Request a view for every visible item.

• Create two more for both directions ( up/down) to avoid flickering of the screen as a new view is created and populated.

• As you scroll, the views going off the screen are recycled and reused for the new views, by just populating the new data.

• Less memory overhead, smoother scrolling and less view management.

Useful links

• Speakers linkedn profile: https://uk.linkedin.com/pub/christoforos-nalmpantis/44/231/23

• Activity lifecycle demo source code: https://github.com/ChristoferNal/activityLifecycle

• PracticeRecyclerVIew source code: https://github.com/ChristoferNal/practiceRecyclerView/tree/develop

Welcome to the Android World!

John Forbes Nash Game Theory