Dagger is a dependency injection framework that allows injecting collaborators into objects without requiring manual passing of dependencies. RxJava implements reactive programming, allowing observable streams to be manipulated through operators like map and filter. Retrofit makes REST API calls simply by defining an interface and allows results to be easily converted to Java objects. Together these libraries help create testable Android applications by decoupling classes and managing dependencies and asynchronous processes in a declarative way.

1. Dagger & RxJava &
Retrofit
Ted

2. what is Dagger
Dagger is a Dependency Injector

3. example1
public class School {
public Teacher teacher = new Teacher();
}

4. Cons?
● school 裡會有很多teacher，但是如果沒有
setter 代表school必須跟teacher綁定
● how to test?

5. example2
public class School {
public Teacher teacher ;
public void setTeacher(Teacher t){
teacher = t;
}
}

6. Pros
● now we can set whoever we want.
● and easy to test

7. TestSample
s = new Schoole();
s.setTeacher(new MockTeacher());
assert.equals(s.getTeacherName(),”balabala”);

8. so...how to use dagger
● source (Module)
● target (class)

9. Source (Module)
create a @Module
tell the module you are going to @Inject to
which class
@Provides a type to that class

10. Target(class)
@Inject the Modules to class
auto @Inject to field or get type by code

11. example1
demo and explain
https://github.
com/nightbear1009/Dagger_StepByStep
repository = feature/simpleDagger

12. example2
demo and explain
https://github.
com/nightbear1009/Dagger_StepByStep
repository = feature/plusIfNecessary

13. what’s the meaning of plus?
AppGraph
NetworkModules
AccountModules

14. what’s the meaning of plus?
AppGraph
NetworkModules
AccountModules
LoginGraph
LoginHelperModules
UserLogin App + Login Graph

15. what’s the meaning of plus?
UserLogout
AppGraph
NetworkModules
AccountModules

16. what about test
override

17. example3
https://github.
com/nightbear1009/Dagger_StepByStep
repository = feature/testTeacher

18. Rxjava
Funtional Programing

19. forEach
rx.Observable.from("1","2","3").forEach(new Action1<String>() {
@Override
public void call(String s) {
Log.d("Ted","s "+s);
}
});
s 1
s 2
s 3

20. map
rx.Observable.from("1","2","3").map(new Func1<String, Boolean>() {
@Override
public Boolean call(String s) {
return s.equals("1");
}
}).subscribe(new Action1<Object>() {
@Override
public void call(Object o) {
Log.d("Ted","o "+o);
}
});
o true
o false
o false

21. flapMap
rx.Observable.from("1","2","3").flatMap(new Func1<String, rx.Observable<?>>() {
@Override
public rx.Observable<?> call(String s) {
Log.d("Ted","num "+s);
return rx.Observable.from(s);
}
}).subscribe(new Action1<Object>() {
@Override
public void call(Object o) {
}
});
num 1
num 2
num 3

22. filter
rx.Observable.from("1","2","3").filter(new Func1<String, Boolean>() {
@Override
public Boolean call(String s) {
return s.equals("1");
}
}).subscribe(new Action1<String>() {
@Override
public void call(String s) {
Log.d("Ted","s "+s);
}
});
s 1

23. toSortedList
rx.Observable.from("1","3","2").toSortedList(new Func2<String, String, Integer>() {
@Override
public Integer call(String s, String s2) {
return Integer.valueOf(s2) - Integer.valueOf(s);
}
}).subscribe(new Action1<List<String>>() {
@Override
public void call(List<String> strings) {
for(String s :strings){
Log.d("Ted","s "+s);
}
}
});
s 3
s 2
s 1

24. groupby
false integer 1 false integer 3
true integer 2 true integer 2 false integer 3
false integer 5 true integer 6 false integer 7
true integer 8 false integer 9

25. Observable.just vs Observable.from
一次丟全部資料和一次丟一筆資料的差別?

26. without publish + connect
D s url1
D s url2
D s url3
D s2 url1
D s2 url2
D s2 url3

27. publish + connect
D s url1
D s2 url1
D s url2
D s2 url2
D s url3
D s2 url3

28. refcount
還沒時間看XD

29. Pros & Cons
Pros
logic will be clear
Cons
high leaning curve
lots of callback(with retrolamda maybe better)

30. Ingram 說
http://ingramchen.
io/blog/2014/10/retromlambda.html

31. 華生大大 說
https://twitter.
com/jakewharton/status/3858989968
84971520

32. 過了幾個月後 華生大大又說..

33. 華生大大 again

34. 都是別人說，現在換我說XD
rxjava的確算是較大型的lib，learning curve比較
高，有很多東西需要花時間學習＆了解.
but如果我們只是用來處理 api + data handle 而
不用來處理複雜的邏輯 or data combining...
(https://github.com/nightbear1009/RxAndroid-
Login-Sample )，
我相信會是個不錯的選擇

35. Retrofit
three steps
1. create interface
2. create api
3. handleData

39. retrofit
1. build in gson
2. no need to implement parcelable
3. easy to test

40. test

41. test more with gradle + dagger
前情提要：
randy: 有沒有可能寫出
XXXListView.get(url) ; 然後就可以畫出layout的
辦法?
https://github.
com/nightbear1009/SmallDaggerRetr
ofitRxjavaSample

42. 當然，目前的版本還有很多高耦合的問題必須解
決，ex : adapter 但或許是個將view 封裝的一個
方向？

43. so… what can we do with these lib
Demo Time again

44. Conclusion
● use Retrofit to handle Network api
● use dagger to injection every retrofit’s
adapter
(so we can mock the api data)
● use rxjava to handle every event including
api call back
(so our logic will be clearly)