The document discusses dependency injection in Android using Dagger, emphasizing its benefits such as decoupling of components, improved testability, and reduced dependency management. It illustrates various examples of dependency injection patterns with code snippets, showcasing how to implement these ideas in Android applications. Additionally, it highlights the use of Dagger for testing and includes references to resources for further exploration.

1. Automated testing
Android
Dependency Injection and Dagger

2. Dependency Injection
Dagger
Live Coding Sample 1
Live Coding Sample 2

3. The Business Goal

4. Why not automated tests on mobile?

5. Motivation for Dependency Injection
● Decouple concrete from concrete
● Uniformity
● Reduced Dependency Carrying
● More Testable Code

6. Decouple concrete from Concrete
class MyStringUtils {
private Context context;
StringUtils(Context context) {
this.context = context;
}
public String helloWorld() {
return context.getString(R.string.hello_ciklum);
}
}

7. Decouple concrete from Concrete
class MainActivity extends Activity implements View.OnClickListener {
@Inject MyStringUtils myStringUtils;
void onCreate(Bundle savedInstanceState) {
… }
void onClick(View v) {
MyStringUtils myStringUtils1 = new MyStringUtils(this.getApplication()); // new operator
MyStringUtils myStringUtils2 = MyStringUtils.getInstance(this); // singleton pattern
MyStringUtils myStringUtils3 = MyStringUtilsFactory.getInstance(this); // factory patterns
String str1 myStr = MyStringUtils.helloWorld(this); // Static
String str = myStringUtils.helloWorld();
TextView msgView = (TextView) findViewById(R.id.textView);
msgView.setText(str);
}}}

8. Uniformity
class MainActivity extends Activity implements View.OnClickListener {
@Inject MyStringUtils myStringUtils;
void onCreate(Bundle savedInstanceState) {
… }
void onClick(View v) {
MyStringUtils myStringUtils1 = new MyStringUtils(this.getApplication()); // new instance
MyStringUtils myStringUtils2 = MyStringUtils.getInstance(this); // Singleton pattern
MyStringUtils myStringUtils3 = MyStringUtilsFactory.getInstance(this); // Factory pattern
String str1 myStr = MyStringUtils.helloWorld(this); // Static
String str = myStringUtils.helloWorld();
TextView msgView = (TextView) findViewById(R.id.textView);
msgView.setText(str);
}
}}

9. Dependency Carrying
class MyActivity extends Activity {
onClick(View v) {
A a = new A(this);
a.doSometing();
}
}
class A {
Context mContext;
public (Context mContext){
this.mContext = mContext;
}
public doSomething() {
B b = new B(mContext);
String str =
b.getSomeString(R.strings.helloWorld);
}
}
class B {
Context mContext;
public B(Context mContext) {
this.mContext = mContext;
}
public String getSomeString(int resourceId) {
return
mContext.getString(resourceId);
}
}

10. Reduced Dependency Carrying
@Module class ProdModule {
Context mContext;
public ProdModule(Context mContext) {
this.mContext = mContext;
}
@Provide B provideB() {
return new B(context);
}
@Provide A provideA(B b) {
return new A(b);
}
}
class MyActivity {
@Inject A a;
onCreate(){
((MyApplication)getApplication()).inject(this);
}
onClick(View v) {
A a = new A(this);
a.doSomething();
}
}
class A {
@Inject B b;
public doSomething() {
String str = b.getSomeString(R.strings.helloWorld);
}
}
class B {
Context mContext;
public B(Context mContext) {
this.mContext = mContext;
}
public String getSomeString(int resourceId) {
return mContext.getString(resourceId);
}
}

11. More Testable Code
class MainActivity extends Activity implements View.OnClickListener {
@Inject MyStringUtils myStringUtils;
void onCreate(Bundle savedInstanceState) {
… }
void onClick(View v) {
String str = myStringUtils.helloWorld();
TextView msgView = (TextView) findViewById(R.id.textView);
msgView.setText(str);
}
}}

12. Other advantages
● More Reusable Code
● More Readable Code
● Reduced Dependencies

13. Dependency Injection
Dagger
Live Coding Sample 1
Live Coding Sample 2

14. DAGger
Direct
Acyclic
Graph

15. Coffee maker
public class CoffeMaker {
@Inject Heater heater;
@Inject Pump pump;
public void brew() {
heater.on();
pump.pump();
System.out.println("coffee!");
heater.off();
}
}

16. class Thermosiphon implements Pump {
Heater heater;
Thermosiphon(Heater heater) {
this.heater = heater;
}
@Override public void pump() {
if (heater.isHot()) {
System.out.println("=> => pumping => =>");
}
}

17. Declare Dependencies
class Thermosiphon implements Pump {
Heater heater;
@Inject
Thermosiphon(Heater heater) {
this.heater = heater;
}
}

18. Satisfy Dependencies
@Module
class DripCoffeeModule {
@Provides Heater provideHeater() {
return new ElectricHeater();
}
@Provides Pump providePump(Thermosiphon pump) {
return pump;
}
}

19. Build the Graph
class CoffeeApp {
public static void main(String[] args) {
ObjectGraph objectGraph = ObjectGraph.create(new
DripCoffeeModule());
CoffeeMaker coffeeMaker = objectGraph.get(CoffeeMaker.class);
coffeeMaker.brew();
} }

20. Neat features
● Lazy<T>
● Module overrides

21. Lazy<T>
class GridingCoffeeMaker {
@Inject Lazy<Grinder> lazyGrinder;
public void brew() {
while (needsGrinding()) {
// Grinder created once and cached.
Grinder grinder = lazyGrinder.get()
grinder.grind();
}
} }

22. Module Overrides
@Module(
includes = DripCoffeeModule.class,
injects = CoffeeMakerTest.class,
overrides = true
)
static class TestModule {
@Provides @Singleton Heater provideHeater() {
return Mockito.mock(Heater.class);
}
}

23. Dependency Injection
Dagger
Live Coding Sample 1
Live Coding Sample 2

24. Live coding - Sample 1
● add dependencies (with Gradle)
● create module
● set up Dagger in Application context
● inject dependencies to Activity
● create Activity test which injects a mock

25. Add depedencies (Gradle)
dependencies {
……...
compile 'com.squareup.dagger:dagger:1.2.1'
compile 'com.squareup.dagger:dagger-compiler:1.2.1'
androidTestCompile 'org.mockito:mockito-core:1.9.5'
androidTestCompile 'com.google.dexmaker:dexmaker:1.0'
androidTestCompile 'com.google.dexmaker:dexmaker-mockito:1.0'
}

26. Module
@Module(
injects = {
MyStringUtils.class, MainActivity.class })
class ProdModule {
Application application;
ProdModule(Application application){
this.application = application;
}
@Provides @Singleton
MyStringUtils provideMyStringUtils() {
return new MyStringUtils(application);
}

27. Define Dagger Application
class MyApplication extends Application {
ObjectGraph mGraph;
void onCreate() {
super.onCreate();
mGraph = ObjectGraph.create(getModules().toArray());
}
void inject(Object o){
mGraph.inject(o);
}
List<Object> getModules() {
List<Object> result = new ArrayList<Object>();
result.add(new ProdModule(this));
return result;
}}

28. Create MyStringUtils
class MyStringUtils {
MyStringUtils(Context context) {
this.context = context;
}
public String helloWorld() {
return context.getString(R.string.hello_ciklum);
}
}

29. Inject dependencies Activity
class MainActivity extends Activity {
@Inject
MyStringUtils myStringUtils;
void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// set dependencies to this activity
((MyApplication)getApplication()).inject(this);
setContentView(R.layout.activity_main);
findViewById(R.id.button).setOnClickListener(this);
}

30. Unit test Activity with mock
class MainActivityUnitTest extends ActivityUnitTestCase<MainActivity> {
@Inject
MyStringUtils myStringUtils;
void setUp() {
// create test application context, Dagger Graph with our test module.
MyApplication application = new TestApplication();
application.inject(this); // inject the dependencies we need to this class
setApplication(application); // use our custom test application context
}
void testOnClick() {
String testingStr = "olala";
when(myStringUtils.helloWorld()).thenReturn(testingStr);
this.activity = startActivity(intent, null, null);
// the test
View view = activity.findViewById(R.id.button);
activity.onClick(view);
// verify the mock was invoked
verify(myStringUtils, times(1)).helloWorld();
// assert view got updated correctly
TextView msgView = (TextView) activity.findViewById(R.id.textView);
assertEquals(testingStr, msgView.getText());
}

31. Dependency Injection
Dagger
Live Coding Sample 1
Live Coding Sample 2

32. Sample app 2
● Threads
● HTTP mocks

33. Tips, tricks and Frameworks
● https://github.com/tha022/dagger-testing-example
● https://github.com/fizz-buzz/fb-android-dagger