Introduction to Android Development

The basics, best practices and the future of Android development

1. Introduction to Android Development Basics, best practices and the future Sérgio Santos from Bloco
2. Overview • Basics • Architecture • Level 1 - Databases, APIs, Compatibility • Level 2 - Testing, Dependency Injection • Future
3. About me
6. Basics
7. Activities
8. Activities
9. Activities (code) public class HomeActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_home); } }
10. Activities (lifecycle)
11. Activities (intents) Intent intent = new Intent(this, HomeActivity.class); startActivity(intent); Uri browerUri = Uri.parse("http://www.google.com"); Intent browserIntent = new Intent(Intent.ACTION_VIEW, browerUri); startActivity(browserIntent);
12. Application
13. Application Manifest <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="io.bloco.intro"> <uses-permission android:name="android.permission.INTERNET"/> <!-- Rest of permissions --> <application android:icon="@mipmap/ic_launcher" android:label="@string/app_name"> <activity android:name=".HomeActivity" android:label="@string/home"> <intent-filter> <action android:name="android.intent.action.MAIN"/> <category android:name="android.intent.category.LAUNCHER"/> </intent-filter> </activity> <activity android:name=".AnotherActivity" android:label="@string/another"> <!-- Rest of activities --> </manifest>
14. Application Build apply plugin: 'com.android.application' android { compileSdkVersion 23 buildToolsVersion "23.2.1" defaultConfig { minSdkVersion 17 targetSdkVersion 23 versionCode 1 versionName "1.0" } } dependencies { compile fileTree(dir: 'libs', include: ['*.jar']) compile 'com.android.support:appcompat-v7:23.2.1' // Rest of dependencies }
15. More application features • Resources • File storage • Preferences (key-value store) • Database (sqlite)
16. Resources
17. res/layout/activity_home.xml <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent"> <EditText android:id="@+id/message" android:layout_width="wrap_content" android:layout_height="wrap_content" android:hint="@string/message" /> <Button android:id="@+id/send" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/send" /> </LinearLayout>
18. res/values/strings.xml <resources> <string name="app_name">Intro</string> <string name="message">Message</string> <string name="send">Send message</string> </resources
19. Using resources public class HomeActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_home); Button sendButton = (Button) findViewById(R.id.send); EditText messageEditText = (EditText) findViewById(R.id.message); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { String message = messageEditText.getText(); Toast.makeText(this, message, Toast.LENGTH_LONG).show(); } }); } }
20. Resources modifiers
21. Fragments + Custom Views
22. Fragments
23. Custom Views <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent"> <io.bloco.intro.AwesomeEditText android:id="@+id/message" android:layout_width="wrap_content" android:layout_height="wrap_content" android:hint="@string/message" /> <Button android:id="@+id/send" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/send" /> </LinearLayout>
24. Custom Views class AwesomeEditText extends EditText { public AwesomeEditText(Context context, AttributeSet attrs) { super(context, attrs); } @Override public Editable getText() { return super.getText().append(" (awesome!)"); } }
25. Architecture
26. Common issues
27. Model – View – Presenter
28. Data binding <layout xmlns:android="http://schemas.android.com/apk/res/android"> <data> <variable name="user" type="io.bloco.intro.User"/> </data> <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@{user.firstName}"/> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@{user.lastName}"/> </LinearLayout> </layout>
29. Data binding @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); HomeActivityBinding binding = DataBindingUtil.setContentView(this,R.layout.activity_home); User user = new User("Sérgio", "Santos"); binding.setUser(user); }
30. Clean Architecture
31. Clean architecture
32. Clean architecture
33. Clean architecture
34. Database
35. Database • Sqlite3 • Content Providers • ORMs • Realm
36. Content Providers // Run query Cursor cur = null; ContentResolver cr = getContentResolver(); Uri uri = Calendars.CONTENT_URI; String selection = "((" + Calendars.ACCOUNT_NAME + " = ?) AND (" + Calendars.ACCOUNT_TYPE + " = ?) AND (" + Calendars.OWNER_ACCOUNT + " = ?))"; String[] selectionArgs = new String[] {"sampleuser@gmail.com", "com.google", "sampleuser@gmail.com"}; // Submit the query and get a Cursor object back. cur = cr.query(uri, EVENT_PROJECTION, selection, selectionArgs, null);
37. Database • Sqlite3 • Content Providers • ORMs • Realm
38. ORMs • OrmLite • SugarORM • GreenDAO • ActiveAndroid • ...
39. Realm Realm realm = Realm.getInstance(this); // All writes are wrapped in a transaction to facilitate safe multi threading realm.beginTransaction(); // Add a person Person person = realm.createObject(Person.class); person.setName("Young Person"); person.setAge(14); realm.commitTransaction(); RealmResults<User> result = realm.where(User.class) .greaterThan("age", 10) // implicit AND .beginGroup() .equalTo("name", "Peter") .or() .contains("name", "Jo") .endGroup() .findAll();
40. APIs
41. Retrofit public interface TwitterService { @GET("timeline/{userId}") Call<List<Tweet>> listTweets(@Path("userId") String userId); } Retrofit retrofit = new Retrofit.Builder() .baseUrl("https://api.twitter.com/") .build(); TwitterService twitterService = retrofit.create(TwitterService.class);
42. Retrofit twitterService .listTweets("sdsantos" ) .enqueue(new Callback<List<Tweet>> { @Override public void onSuccess(Call<List<Tweet>> call, Response<List<Tweet>> response) { List<Tweet> tweets = request.body(); // Do something with tweets } @Override public void onError(ApiError apiError) { // Show error } });
43. Compatibility
44. Compatibility • V4 Support Library • V7 Support Library • Design Support Library
45. Testing
46. Instrumentation Testing
47. Instrumentation Testing with Espresso @RunWith(AndroidJUnit4.class) public class CalculatorActivityTest { @Rule public ActivityTestRule<CalculatorActivity> activityTestRule = new ActivityTestRule<>(CalculatorActivity.class); @Test public void testSum() throws Exception { onView(withId(R.id.calculator_input)) .perform(typeText("2 + 2")) onView(withText("=")) .perform(click()); onView(withId(R.id.calculator_result)) .check(matches(withText("4"))); } }
48. Unit Testing
49. Unit Testing with Mockito class Controller { private final Database database; private final Screen screen; public Controller(Database database, Screen screen) { this.database = database; this.screen = screen; } public void check() { List<String> fruits = database.getFruits(); if (fruits.isEmpty()) { screen.showEmptyMessage(); } else { screen.showFruits(fruits); } } }
50. Unit Testing with Mockito public class ControllerTest extends AndroidTestCase { private Controller controller; private Database database; private Screen screen; @Override protected void setUp() throws Exception { super.setUp(); database = mock(Database.class); screen = mock(Screen.class); controller = new Controller(database, screen); } // Tests... } // Tests public void testCheckWithFruit() { List<String> fruits = new ArrayList<>(); fruits.add("banana"); fruits.add("apple"); when(database.getFruits()).thenReturn(fruits); controller.check(); verify(screen).showFruits(eq(fruits)); } public void testCheckEmpty() { List<String> emptyFruits = new ArrayList<>(); when(database.getFruits()).thenReturn(emptyFruits); controller.check(); verify(screen).showEmptyMessage(); }
51. Dependency Injection
52. Dependencies // Avoid class Foo { public Foo() { Bar bar = new Bar(); // or Bar.getInstance() bar.something(); } } new Foo(); // Better class Foo { public Foo(Bar bar) { bar.something(); } } new Foo(new Bar());
53. Dependencies // Perfect interface Bar { void something() } class MyBar implements Bar { @Override public void something() { // ... } } class Foo { public Foo(Bar bar) { bar.something(); } } new Foo(new MyBar());
54. Dependency Injection // Goal class Foo { @Inject public Foo(Bar bar) { bar.something(); } } Dagger v1: http://square.github.io/dagger/ Dagger v2: http://google.github.io/dagger/
55. Future
56. Reactive
57. Theory vs real architecture
58. Kotlin
59. Kotlin
60. Resources
61. Resources • Google Codelabs: https://codelabs.developers.google.com • Android development like a pro: https://speakerdeck.com/rallat/android-development-like-a-pro • Fernando Cejas: http://fernandocejas.com • Kotlin 101: https://speakerdeck.com/ivanbruel/kotlin-101 • Bloco’s blog: https://bloco.io/blog
62. @sdsantos www.bloco.io hello@bloco.io Introduction to Android Development