Android: GUI Development

A brief introduction and getting-started guide.

Ove

rvie

w • What is Android?– Introduction– Architecture– Activities, Views, Intents

• Android Developer Tools– Installing the Android SDK– Setting up an AVD

• Demo– Creating a project, project structure– Building and deploying to an AVD– Using MVC

• Wrap-up– Tips & Tricks

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Res

ourc

es

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http://developer.android.com

http://developer.android.com/

Wha

t is

And

roid

? • Pervasive Mobile Platform– Runs on billions of mobile phones, tablets– World’s most popular & frequently installed mobile OS– Open Source (minimum-definition).

• Developing on Android– Multi-platform tools– Based on Java– Uses Android Studio IDE– Excellent third-party tools support

• See http://developer.android.com/tools/index.html

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Arc

hite

ctur

e • Layered environment– Bottom tier: Linux 2.6 kernel– Mid tier: Android libraries/services– Top tier: Java applications

• Applications run in virtual machines (VM)– Each application has it’s own VM & address space– Restrictions on sharing resources and data– Dalvik virtual machine process

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Arc

hite

ctur

e

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Des

ign

Goa

ls • Applications provide multiple entry points; they’re distinct components that can be invoked individually.– Applications are typically composed of individual,

standalone screens.– Explicitly need to pass data between screens (reduces

overhead/memory).• Applications are dynamic

– You should provide different layouts (XML layouts, and resources) based on device characteristics.

– Applications should dynamically adjust based on device screen size and orientation.

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http://developer.android.com/guide/index.html

Des

ign

Con

side

ratio

ns • Limited resources– Limited memory, processing power– Battery life is critical!

• Architectural tradeoffs– The OS aggressively flushes memory– Background computation is limited

• Unusual device characteristics– Small screen– Multiple orientations, dynamic layout– Single window/application running– Multi-touch input

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Ove

rvie

w • What is Android?– Introduction– Architecture– Activities, Views, Intents

• Android Developer Tools– Installing the Android SDK– Setting up an AVD

• Demo– Creating a project, project structure– Building and deploying to an AVD– Using MVC

• Wrap-up– Tips & Tricks

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Act

iviti

es • Different types of components that we can build in Android: applications, services, etc. (see chart below)

• A standard application component is an Activity– Typically represents a single screen– Main entry point (equivalent to main() method)– For most purposes, this is your application class!

Components Description

Activity Single-screen of an application

Service Long-running background application

Content provider Provides shared set of application data

Broadcast receiver Responds to system broadcast events

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Act

ivity

Life

cycl

e • Activities have an explicit lifecycle– One activity runs at a time, others are paused in the background.– As users navigate through your application, they switch activities.

• Every activity has a state: run, paused, or stopped.- Changing state fires a corresponding activity method.

Running Paused/ Stopped

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Act

ivity

Life

cycl

e • Common to switch between different activities/screens.– Activities can create other activities (“Back stack”)– Navigation forward/back through activities is typically triggered

by user actions

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Inte

rrup

ted

Wor

kflo

w • Applications can stop at any time (i.e. user quits, OS kills it). – Each activity needs to manage its own state.– Activities have methods for saving and restoring state

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http://developer.android.com/training/basics/activity-lifecycle/pausing.html

Inte

nts • We use intents to pass data between activities/screens.

– Data structure holding an abstract description of an action.– Use Activity startActivity() method to launch with intent.

• Explicit (named activity) vs. implicit (capabilities, e.g. camera)

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https://developer.android.com/guide/components/intents-filters.html

Opt

iona

l: Fr

agm

ents • Fragments can be thought of as

portions of a UI• An activity can contain (and

manage) multiple fragments.– Allows for dynamic

adjustments to the UI– Fragments have their own

lifecycle, and their own layout.– Alternative to multiple activities

CS349 -- Direct Manipulation15

http://developer.android.com/guide/components/fragments.html

UI C

ompo

nent

s • android.view.ViewGroup– Abstract container class– Includes layout functionality directly– Subclasses: FrameLayout, GridLayout, LinearLayout,

RelativeLayout, Toolbar, …

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• android.view.View– Base widget class (drawing and

event handling)– Subclasses:

• android.widget.Button• android.widget.ImageView• android.widget.ImageButton• android.widget.ProgressBar …

Layo

ut • Layout can be handled in one of two ways:1. Programmatically. You write code to instantiate

ViewGroups, Views and bind them together (sim. to how you’ve done this in Java).

2. Use XML to describe your layout. In-code, describe the screen elements (view groups and views) along with properties, and then tell your application to dynamically load it.

• Using XML is actually the preferred way to handle this.– Android Studio includes a GUI builder to make this easier!

CS349 -- Direct Manipulation17

Rec

ap: B

uild

ing

App

licat

ions A typical application will include:

• Activities – MainActivity as your entry point– Possibly other activities (corresponding to multiple screens)

• Views– Screen layouts– ViewGroups containing Views (i.e. components)

• Intents– Only required if you need to communicate or pass data

between screens

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Ove

rvie

w • What is Android?– Introduction– Architecture– Activities, Views, Intents

• Android Developer Tools– Installing the Android SDK– Setting up an AVD

• Demo– Creating a project, project structure– Building and deploying to an AVD– Using MVC

• Wrap-up– Tips & Tricks

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And

roid

Stu

dio

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• Android Studio• Released by Google, based on IntelliJ• Runs on Mac, Windows, Linux

• Install from the Android Developer Portal• Develop -> Tools

• Single installation includes• IDE (GUI)• Software Development Kit

(SDK) includes compiler, debugger, profiler etc.

• Documentation• Sample code

Working in a text editor is NOT

recommended –you need an IDE.

And

roid

SD

K M

anag

er • Android SDK Manager can be used to install components, sample code, documentation, etc.– Android Studio: Tools -> Android -> SDK Manager

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And

roid

Virt

ual D

evic

e (A

VD) • Android Virtual Device is an emulator, that can emulate a range of

devices/capabilities/OS versions (so that you don’t need a physical device to develop or test your code).– Android Studio: Tools -> Android -> AVD Manager

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Ass

ignm

ent

Setu

p • Required Development Tools– Android Studio 2.1 (or later) on Mac, Windows or Linux– Android 6.0 Marshmallow (API 23) (installed by default)

• Project Setup– Create with the New Android Application wizard

• Blank Activity (accept defaults)• AVD Setup

– Create a Nexus 7 tablet device, with defaults• Marshmallow: API 23, ABI x86• Landscape orientation

– Advanced Settings• VM Heap: 256 MB

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Get

ting

Star

ted 1. Install Android Studio

2. Create an empty project– Use the New Project wizard in Android Studio.

3. Setup the Android Virtual Device (AVD)– Configure the emulator for your target device.

4. Specify the Run Configuration -- optional– Specify the starting Activity that will be used, and the target

(typically the AVD that you configured above).5. Build and test6. Commit and push everything to your Git repo

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Ove

rvie

w • What is Android?– Introduction– Architecture– Activities, Views, Intents

• Android Developer Tools– Installing the Android SDK– Setting up an AVD

• Demo– Creating a project, project structure– Building and deploying to an AVD– Using MVC

• Wrap-up– Tips & Tricks

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Dem

o • The New-Project wizard generates “Hello World” starter code.• Great demonstration of how the project fits together.• Recall the application lifecycle. Event states map directly to

methods.

Running Paused/ Stopped

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“Hel

lo W

orld

”

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• OnCreate() - executed when the app runs• SetContentView(R.layout.activity_main) - Uses layout from

res/layout/activity_main.xml

“Hel

lo W

orld

”

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Dem

o: M

VC A

pplic

atio

n • To implement MVC, we can instantiate our model, view and controller classes directly in code.– Define views using resource files, but use code to

instantiate them and bind them together.• See android_examples.zip on course website

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Ove

rvie

w • What is Android?– Introduction– Architecture– Activities, Views, Intents

• Android Developer Tools– Installing the Android SDK– Setting up an AVD

• Demo– Creating a project, project structure– Building and deploying to an AVD– Using MVC

• Wrap-up– Tips & Tricks

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Tips

& T

ricks • AVD

– The AVD is slow to launch, so keep it running in the background while you’re programming / debugging.

• Use the debugging tools in Android Studio– You can set breakpoints etc. as usual– logcat shows device output and you can write to it using the

android.util.Log class (sim. to printf).

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Res

ourc

es • Android Developer http://developer.android.com/• Android Developer Channel @YouTube

– http://www.youtube.com/user/androiddevelopers• Android Open Source Project https://source.android.com• Recommended (Optional!) Books

– Phillips & Hardy, Android Programming: The Big Nerd Ranch Guide

– Mednieks et al., Programming Android

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