Android Dependencies You Can Depend On

Transcript

1. Android Dependencies
   You Can Depend On
   Dan Lew
   3/21/2015
   

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2. Why Libraries?
   • Stand on the shoulders of giants
   • Hit the ground running
   • Easier than ever to use
   

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3. Adding Libraries
   repositories {

   jcenter()

   }

   

   dependencies {

   compile 'com.squareup.retrofit:retrofit:1.9.0'

   }
   

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4. Which Libraries?
   

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5. My Basic Stack
   • Retrofit
   • GSON
   • Picasso
   • OkHttp
   • Dagger
   • RxJava
   

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6. Retrofit
   • …Because a lot of people use REST
   • …Because REST is easy to understand
   

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7. Example API
   http://company.com/api/public/cards?id=someId
   

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8. Define an Interface
   http://company.com/api/public/cards?id=someId
   public interface MyService {

   

   @GET("/api/{visibility}/cards")

   List getCards(@Path("visibility") String visibility, 

   @Query("id") String id);

   

   }
   

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9. Create a RestAdapter
   RestAdapter restAdapter = new RestAdapter.Builder()

   .setEndpoint("http://company.com")

   .build();

   

   MyService service = restAdapter.create(MyService.class);
   

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10. Use the service
    List cards = service.getCards("public", "someId");
    

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11. GSON
    • …Because many REST APIs use JSON
    

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12. JSON vs. Object
    • JSON
    {

    "id": "someId",

    "data": "Some data"

    }
    • Class
    public class Card {

    

    private String id;

    

    private String data;

    

    }
    

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13. Without GSON
    String jsonStr = /* …what we had from before… */;

    try {

    JSONObject jsonObject = new JSONObject(jsonStr);

    String id = jsonObject.getString("id");

    String data = jsonObject.getString("data");

    Card card = new Card(id, data);

    } catch (JSONException e) {

    e.printStackTrace();

    }
    

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14. With GSON
    String jsonStr = /* ...whatever you get from Retrofit... */;

    Gson gson = new Gson();

    Card card = gson.fromJson(jsonStr, Card.class);
    

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15. Customizable
    • Can handle differently named fields:
    public class Card {

    

    @SerializedName("theId")

    private String id;

    

    @SerializedName("theData")

    private String data;

    

    }
    • Custom deserializers (type adapters)
    

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16. Retrofit with GSON
    RestAdapter restAdapter = new RestAdapter.Builder()

    .setEndpoint("http://company.com")

    .setConverter(new GsonConverter(new Gson()))

    .build();

    

    MyService service = restAdapter.create(MyService.class);
    

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17. Picasso
    • Easy image loading
    Picasso.with(this)

    .load("http://path.to/image.png")

    .into(someImageView);
    

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18. Picasso Options
    Picasso.with(this)

    .load("http://path.to/image.png")

    .placeholder(R.drawable.placeholder)

    .centerCrop()

    .into(someImageView);
    

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19. OkHttp
    • Consistent HTTP implementation
    • Better HTTP implementation
    • Easier HTTP implementation
    • Drives other libraries
    

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20. OkHttp + Retrofit
    • Add client to RestAdapter
    RestAdapter restAdapter = new RestAdapter.Builder()

    .setEndpoint("http://company.com")

    .setConverter(new GsonConverter(new Gson()))

    .setClient(new OkClient())

    .build();
    

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21. OkHttp + Picasso
    Picasso picasso = new Picasso.Builder()

    .downloader(new OkHttpDownloader())
    .build();
    

    picasso.load("http://path.to/image.png")

    .into(someImageView);
    

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22. Dagger
    • Dependency injection!
    • …What does that really mean?
    • …Why do you want it?
    

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23. Components
    • RestAdapter
    • Gson
    • Picasso
    • OkHttp
    • …All intertwined
    

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24. BAD
    • DO NOT create new instances each time!
    RestAdapter restAdapter = new RestAdapter.Builder()

    .setEndpoint("http://company.com")

    .setConverter(new GsonConverter(new Gson()))

    .setClient(new OkClient())

    .build();
    

    MyService service = restAdapter.create(MyService.class);
    Picasso picasso = new Picasso.Builder()

    .downloader(new OkHttpDownloader()).build();
    

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25. Solving the Bad
    • Problem: Need to cache components
    • Solution: static singletons!
    

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26. It is now impossible to
    test most of your code
    

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27. Solution
    Dependency injection!
    

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28. It’s Not Complex
    • Without dependency injection
    public class SomeClass {

    private SomeService service;

    

    public SomeClass() {

    this.service = new SomeService();

    }

    }
    • With dependency injection
    public class SomeClass {

    private SomeService service;

    

    public SomeClass(SomeService service) {

    this.service = service;

    }

    }
    

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29. Unfortunately…
    • Passing around dependencies is a PITA!
    • Dagger: Handles busywork for you
    

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30. Dagger Modules
    @Module

    public class AppModule {

    

    @Provides @Singleton Gson provideGson() {

    return new Gson();

    }

    

    @Provides @Singleton Client provideClient() {

    return new OkClient();

    }

    

    @Provides @Singleton RestAdapter provideRestAdapter(Gson gson,

    Client client) {

    return new RestAdapter.Builder()

    .setConverter(new GsonConverter(gson))

    .setClient(client)

    .build();

    }

    

    @Provides @Singleton MyService provideMyService(RestAdapter restAdapter) {

    return restAdapter.create(MyService.class);

    }

    }
    

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31. Injecting Modules
    public class SomeClass {

    

    @Inject MyService myService;

    

    public SomeClass() {

    // In real life, ObjectGraph should be reused

    ObjectGraph objectGraph = ObjectGraph.create(new AppModule());

    objectGraph.inject(this);

    }

    

    }
    

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32. RxJava
    • Reactive framework
    • Less coding
    • Easy error handling
    • Easy concurrency
    • Just plain fun
    • …But not easy to understand at first
    

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33. Observer Pattern
    Observable.just("1", "2", "3")

    .subscribe(new Action1() {

    @Override public void call(String s) {

    System.out.println(s);

    }

    });
    

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34. Operators
    Observable.just("1", "2", "3")

    .map(new Func1() {

    @Override public String call(String s) {

    return "item: " + s;

    }

    })

    .subscribe(new Action1() {

    @Override public void call(String s) {

    System.out.println(s);

    }

    });
    

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35. Schedulers
    Observable.just("1", "2", "3")

    .map(new Func1() {

    @Override public String call(String s) {

    return "item: " + s;

    }

    })

    .subscribeOn(Schedulers.io())

    .observeOn(AndroidSchedulers.mainThread())

    .subscribe(new Action1() {

    @Override

    public void call(String s) {

    System.out.println(s);

    }

    });
    

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36. Error Handling
    Observable.just("1", "2", "3")

    .map(new Func1() {

    @Override

    public String call(String s) {

    return "item: " + s;

    }

    })

    .subscribeOn(Schedulers.io())

    .observeOn(AndroidSchedulers.mainThread())

    .subscribe(

    new Action1() {

    @Override public void call(String s) {

    System.out.println(s);

    }

    },

    new Action1() {

    @Override public void call(Throwable throwable) {

    System.out.println("Something went wrong!");

    }

    });
    

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37. u2020
    • Great sample for (most) of basic stack
    • https://github.com/JakeWharton/u2020/
    

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38. Alternatives
    • Everything has alternatives
    • Impact, not implementation
    • Weigh pros/cons
    

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39. Development Libraries
    

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40. Stetho
    • Debug bridge on Chrome
    

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41. Stetho
    • Debug bridge on Chrome
    

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42. Hugo
    • Before:
    public void doSomething(String input) {

    Log.i("SomeTagYouMadeUp", "doSomething(" + input + ")");

    // Shockingly, this does something

    Log.i("SomeTagYouMadeUp", "doSomething finished");

    }
    • After:
    @DebugLog

    public void doSomething(String input) {

    // Shockingly, this does something

    }

    

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43. Timber
    • Smarter alternative to Log
    Timber.i("Something bad happened", exception);
    

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44. gradle-versions-plugin
    • Keep your dependencies up-to-date
    • https://github.com/ben-manes/gradle-versions-
    plugin
    

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45. Fun Libraries
    • Calligraphy - Automatic fonts!
    • Gradle retrolambda - Lambdas in Android!
    • Butterknife - Annotated views!
    • RoundedImageView - Easy rounded corners!
    • Mockito - Mocked objects for testing!
    • Victor - SVGs as resources!
    

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46. Finding Libraries
    

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47. Collections
    • Explore: https://android-arsenal.com/
    • Demo: https://play.google.com/store/apps/details?
    id=com.desarrollodroide.repos
    

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48. Gradle, Please
    • Shortcut for getting exact dependency string
    • http://gradleplease.appspot.com
    

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49. Google
    • A search engine: http://google.com
    • Type in what you want
    • Take a gamble with “I’m feeling lucky”
    

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50. Thank You!
    • http://blog.danlew.net
    • @danlew42
    • +DanielLew
    

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