A simple, scalable app architecture with Android annotations Luke - - PowerPoint PPT Presentation

A simple, scalable app architecture with Android annotations

Luke Sleeman Freelance Android developer lukesleeman.com.au Image CC: https://flic.kr/p/6oqCZB

Agenda

• Introduction
• The architecture - an overview
• Services
• Domain object
• Testing
• UI
• Other issues
• Closing thoughts

Introduction - why we need this at all

Goals

• Quick, simple
• Typically data driven apps - get some stuff from a web service, store it

locally, show it to the user, submit stuff back to the web service

• Scalable - Handle small apps and big ones
• Unsurprising, easy to jump in and out of, clear and concise, makes

sense to anybody. ‘Obvious’.

• Testable
• Need to be able to incrementally evolve towards it from an existing

codebase

• Boring!

The architecture!

User Interface Domain objects Services

This is what it looks like

So what about Android annotations?

User Interface Domain objects Services

AndroidAnnotations

What is AndroidAnnotations?

• Annotate your code - works of JDK annotations
• Code generation - you can look behind the

curtain to see how the magic works. MyActivity_

• Includes annotation support for a lot of other

libraries I use such as ormlite

• You don’t have to use it
• But you would be silly not to :-)

Services

User Interface Domain objects Services

Typical methods

List<Users> getUsersFromWebservice()

• AndroidDatabaseResults searchForSite(String searchText)
• UserInfo getInfoFromFacebook(int key)

A Simple Service

public class PizzaService { private static List<Pizza> pizzas; public static List<Pizza> getPizzas(){ if(pizzas == null){ pizzas = new ArrayList<Pizza>(); pizzas.add(new Pizza("Luke Special", 10.50)); pizzas.add(new Pizza("Margherita", 9.50)); } return pizzas; } }

A more complex service

@EBean(scope = EBean.Scope.Singleton)
 public class FriendService { @OrmLiteDao(helper = ExampleDBHelper.class, model = Friend.class)
 protected RuntimeExceptionDao<Friend, String> friendsDao; @RestService
 protected FriendListWebservice webservice; public List<Friend> getFriends(){
 return friendsDao.queryForAll();
 } public void downloadAndSaveFriend(int id)throws IOException {
 Friend newFriend = webservice.getFriend(id);
 friendsDao.create(newFriend);
 }
 }

Domain objects

User Interface Domain objects Services

A simple domain object

public class Pizza {

• private String name;

private double price;

• public Pizza(String name, double price) {

this.name = name; this.price = price; }

• public String getName() {

return name; }

• public void setName(String name) {

A more complex domain

• bject

@DatabaseTable
 public class Friend {

• @DatabaseField(generatedId = true)


private int id;

• @DatabaseField


private String userName;

• public int getId() {


return id;
 }

• public void setId(int id) {


this.id = id;
 }

• public String getUserName() {


return userName;


Domain objects Relationships

Domain objects Relationships

• Option 1 - In the objects

@ForeignCollectionField(foreignFieldName = "user")
 private List<EmailAddress> addresses;

• Option 2 - In the service

public List<EmailAddress> getFriendEmails(int id)

Unit tests

User Interface Domain objects Services Unit Tests

A basic test

public class PizzaTest extends AndroidTestCase{ public void testGetPizzas(){ List<Pizza> pizzaList = PizzaService.getPizzas(); assertNotNull(pizzaList); } }

• public class FriendTest extends AndroidTestCase {

public void testFriend(){ FriendService friendService = FriendService_.getInstance_(getContext()); assertNotNull(friendService.getFriends()); } }

A more advanced test

public class FriendTest extends AndroidTestCase { @Override
 protected void setUp() throws Exception {
 File database = getContext().getDatabasePath(ExampleDBHelper.DB_NAME);
 if (database.exists()) {
 database.delete();
 }
 } public void testSearchFriends(){
 FriendService service = FriendService_.getInstance_(getContext());
 service.createOrUpdateFriend(new Friend("Luke"));
 assertEquals(1, friendService.search("lu").size());
 } }

A nifty trick

public void downloadAndPatchFriendList() 
 throws IOException{ String patchFile = downloadPatchFile();
 List<Friend> updatedFriends = parsePatch(patchFile);
 mergeFriendsWithDB(updatedFriends); }

A nifty trick

@EBean(scope = EBean.Scope.Singleton)
 public class TestFriendService extends FriendService { @Override
 public void mergeFriendWithDB(List<Friend> updatedFriends){
 super.mergeFriendsWithDB(updatedFriends);
 } @Override
 public List<Friend> parsePatch(String patchFile) {
 return super.parsePatch(patchFile);
 } }

A nifty trick

private TestFriendService testFriendService = 
 TestFriendService_.getInstance_(getContext());

• public void testParseEmpty(){

List<Friend> friends = testFriendService.parsePatch(EMPTY_PATCH); assert... }

• public void testParseModifyFriends(){

List<Friend> friends = testFriendService.parsePatch(MODIFY_PATCH); assert... }

The UI

User Interface Domain objects Services

This is where android annotations really shines

• @EActivity, @EFragment, @EViewGroup
• @ViewByID @FragmentByID, etc
• @DrawableRes @AnimationRes, @HtmlRes
• @Click, @ListClick

Getting services and domain objects

@EActivity(R.layout.activity_best_friend)
 public class BestFriendActivity extends Activity { @ViewById(R.id.best_friend_text)
 protected TextView bestFriendText; @Bean
 protected FriendService friendService; private Friend bestFriend; @AfterViews
 protected void setupBestFriend(){
 bestFriend = friendService.getBestFriend();
 bestFriendText.setText(bestFriend.getName());
 } @Click(R.id.poke_friend_button)
 protected void poke(){
 friendService.poke(bestFriend);
 } }

Threading

@EActivity(R.layout.activity_friend_list)
 public class FriendListActivity extends Activity { @ViewById(R.id.friend_list)
 protected ListView list; @ViewById(R.id.loading_progress)
 protected ProgressBar progressSpinner; @Bean
 protected FriendService service; @AfterViews
 protected void startDownload(){
 progressSpinner.setVisibility(View.VISIBLE);
 downloadFriends();
 }

Threading

@Background
 protected void downloadFriends(){
 try{ List<Friends> friendList = service.downloadFriendList();
 displayFriends(friendList);
 }
 catch(IOException e){
 displayDownloadError();
 }
 } @UiThread
 protected void displayFriends(List<Friends> friendList){
 progressSpinner.setVisibility(View.GONE);
 …
 }

• @UiThread


protected void displayDownloadError(){
 progressSpinner.setVisibility(View.GONE);
 …
 } }

There is a bug!

Threading

@Background
 protected void downloadFriends(){
 try{ List<Friends> friendList = service.downloadFriendList();
 displayFriends(friendList);
 }
 catch(IOException e){
 displayDownloadError();
 }
 } @UiThread
 protected void displayFriends(List<Friends> friendList){
 progressSpinner.setVisibility(View.GONE);
 …
 }

• @UiThread


protected void displayDownloadError(){
 progressSpinner.setVisibility(View.GONE);
 …
 } }

Threading - dealing with activity shutdown

• Option 1 - Let our background task run and don’t update ui

@UiThread
 protected void displayFriends(List<Friend> friendList){
 if(isDestroyed()) return;
 …

Option 2 - Cancel background task
 


@Background(id = "download")
 protected void downloadFriends(){ …. }
 
 @Override
 protected void onDestroy() {
 BackgroundExecutor.cancelAll("download", false);
 super.onDestroy();
 }

Other issues

Evolving an existing apps architecture

• 1. Add in android annotations and clean out

boilerplate

• 2. If you don’t have them start creating domain
• bjects - move logic from UI into them.
• 3. If you don’t have them start creating services -

have them mange your domain objects

Things to look at changing

• Different libraries replace AA (dagger, retrofit,

butterknife)

• EventBus or RXJava
• Pinch ideas from the google io app.
• Come up with a good way to manage fragments

Closing thoughts

A humble request

• Architecture is important!
• Don’t be satisfied with just the simple architecture

presented …

• Think about architecture!
• Talk about architecture!
• Develop new architectures!

Questions?

Bonus slides

When not to use this architecture

• Games
• If your building one app over the course of years
• If you can develop a large internal library of

reusable components