Apply software principles to android development

Apply software principles to android development

Transcript

1. APPLY SOFTWARE PRINCIPLES TO ANDROID DEVELOPMENT Orhan Obut
2. Implement Mobile development process Find an idea Define requirements Backend API, Design Test Publish
3. Reality Find an idea Implement Backend API, Design Define requirements Test Submit
4. Flexibility ? Solution Software principles Design patterns
6. • displayLogin • displayRegistration • displayHome AuthActivity • displayRegistration • makeLoginRequest • displayHome LoginFragment • displayLogin • makeRegistrationRequest • displayHome RegistrationFragment
7. Entities should have only one responsibility. Responsibility is “a reason for change”. Single responsibility Entities should have only one
8. public class LoginFragment extends Fragment { void onLoginClicked() void makeLoginRequest() void displayHome() void onRegisterClicked() void displayRegistration() }
9. AuthActivity • displayLogin() • makeLoginRequest() • parseToUser() • makeRegisterRequest() • displayHome() • onLoginClicked() • onRegisterClicked() • onRegisterClicked() • onLoginClicked() LoginFragment RegistrationFragmentt
10. View Listener Login Fragment Login Presenter
11. public class AuthActivity extends Activity { void onLoginClicked(){} void makeLoginRequest(){ HttpPost httpPost = new HttpPost(URL); HttpClient client = new DefaultHttpClient(); HttpResponse response = client.execute(httpPost); } User parseToUser(String json){ JSONObject jsonObject = new JSONObject(content); String name = jsonObject.getString("name"); } void displayHome(){} void onRegisterClicked(){} void displayRegistration(){} }
12. • displayLogin() • displayRegistration() • displayHome() • onLogin() AuthActivity ApiManager • login() • register() • parseToUser() public class ApiManager { void login(Callback callback){} User parseToUser(String content){} void register(Callback callback){} } public class AuthActivity extends Activity { ApiManager apiManager = new ApiManager(); void onLogin(){ apiManager.login(callback); } }
13. ApiManager • login() • register() • parseToUser() public class ApiManager { void login(Callback callback){ ... User user = parseToUser(json); } User parseToUser(String content) { JSONObject jsonObject = new JSONObject(content); String name = jsonObject.getString("name"); return new User(name); } }
14. public class ApiManager { Gson gson = new Gson(); void makeLoginRequest(Callback callback){ ... User user = gson.fromJson(json, User.class); } } ApiManager • login() • register() Gson • toJson() • fromJson()
15. Auth Activity Login Fragment Registration Fragment Api Manager Gson Home Fragment
16. Open/Closed principle Entities should be open for extension but closed to modification.
17. Close for modification but how? • Use abstraction (stay tuned) • Make all variables private • Avoid global variables as much as possible
18. Login Fragment Api Manager Gson Registration Fragment Home Fragment Home Activity Base Activity Auth Activity
19. public class MyView extends View { boolean editMode; @Override public void setBackgroundColor(int color) { if (editMode) { super.setBackgroundColor(Color.WHITE); return; } super.setBackgroundColor(color); } } for (View view : views) { view.setBackgroundColor(Color.BLACK); }
20. Liskov’s Substitution Derived types must be completely substitutable for their base types.
21. public class MyView extends View { boolean editMode; @Override public void setBackgroundColor(int color) { super.setBackgroundColor(color); } public void setBackground(int color) { if (editMode) { super.setBackgroundColor(Color.WHITE); return; } super.setBackgroundColor(color); } }
22. class ImageActivity extends Activity { @Override public void onCreate(Bundle bundle) { super.onCreate(savedInstance); // init some variables } @Override public void onDestroy() { // free some memory } public void showGalery() public void dismissGalery() public void takePhoto() } class AccountActivity extends ImageActivity { @Override public void onCreate(Bundle bundle) { // init } public void onAvatarClicked() { showGalery(); } public void onTakePhotoClicked() { takePhoto(); } }
23. public class ProductActivity extends ImageActivity { @Override public void onCreate(Bundle bundle) { // init } public void onNewPhotoClicked() { showGalery(); } public void onTakePhotoClicked() { takePhoto(); } }
24. class ShareActivity extends BaseActivity { @Override public void onCreate(Bundle bundle) { // init some fields } public void showGalery() {} public void dismissGalery() {} } class ProductListActivity extends ShareActivity { @Override public void onCreate(Bundle bundle) { // init } public void onShareClicked() { showGalery(); } public void onDismissClicked() { dismissGalery(); } }
25. ShareAndImage Activity Share Activity Base Activity Image Activity Product Activity Account Activity ProductList Activity
26. class ImageActivity extends BaseActivity { @Override public void onCreate(Bundle bundle) { super.onCreate(savedInstance); // init some variables } @Override public void onDestroy() { // free some memory } public void showGalery(){} public void dismissGalery(){} public void takePhoto(){} } class ShareActivity extends BaseActivity { @Override public void onCreate(Bundle bundle) { // init some fields } public void showGalery() {} public void dismissGalery() {} }
27. Favor composition over inheritance
28. class ImageHelper { void onCreate() void onDestroy() void showGalery() void dismissGalery() void takePhoto() } class AccountActivity extends BaseActivity { ImageHelper imageHelper; @Override public void onCreate(Bundle bundle){ imageHelper.onCreate(); } @Override public void onDestroy() { imageHelper.onDestroy(); } public void onAvatarClicked() { imageHelper.showGalery(); } public void onTakePhotoClicked() { imageHelper.takePhoto(); } }
29. public class ImageHelper { public void onCreate() public void onDestroy() public void showGalery() public void dismissGalery() public void takePhoto() } public class ShareHelper { public void onCreate() public void showGalery() public void dismissGalery() } class ShareAndImageActivity extends BaseActivity { ImageHelper imageHelper; ShareHelper shareHelper; @Override public void onCreate(Bundle bundle) { ... imageHelper.onCreate(); shareHelper.onCreate(); } public void onGaleryClicked() { imageHelper.showGalery(); } public void onShareClicked() { shareHelper.showGalery(); } }
30. Base Activity ShareAndImage Activity Product Activity Account Activity ProductList Activity
31. AuthActivity LoginFragment public class LoginFragment extends Fragment { void onLoginClicked() { ((AuthActivity) getActivity()).onLogin(); } }
32. Dependency Inversion Depend upon abstractions
33. AuthActivity LoginFragment LoginListener class AuthActivity extends Activity implements LoginListener { @Override public void onLogin(){ apiManager.login(); } @Override public void onRegister() { apiManager.register(); } } interface LoginListener { void onLogin(); void onRegister(); } class LoginFragment extends Fragment { LoginListener listener; void onLoginClicked() { listener.onLogin(); } void onRegisterClicked() { listener.onRegister(); }
34. LoginFragment AuthActivity class AuthActivity extends Activity implements LoginListener { @Override public void onLogin(){ apiManager.login(new Callback(){ @Override public void onSuccess(){ LoginFragment fragment = (LoginFragment) getFragmentManager() .findFragmentByTag("LoginFragment"); fragment.addItems(items) } }); } }
35. LoginFragment LoginActivity Bus or RxJava
36. Api Manager Auth Activity public class AuthActivity extends Activity { ApiManager apiManager = new ApiManager(); void login(){ apiManager.login(callback); } }
37. Api Manager Auth Activity Api Service public class AuthActivity { ApiService api = new ApiManager(); void login(){ api.login(callback); } } interface ApiService { void login(); void register(); } class ApiManager implements ApiService{ Gson gson = new Gson(); @Override public void login() {} @Override public void register() {} }
38. Gson Api Manager public class ApiManager implements ApiService { Gson gson = new Gson(); @Override public void login() { ... User user = gson.fromJson(body, User.class); } @Override public void register() {} }
39. Gson Api Manager Parser class ApiManager implements ApiService { Parser parser = new GsonParser(); @Override public void login() { ... parser.fromBody(data, User.class); } @Override public void register() {} } public interface Parser { String toBody(...); <T> T fromBody(...); } class GsonParser implements Parser { Gson gson = new Gson(); @Override String toBody(...) { gson.toJson(object); } @Override <T> T fromBody(...){ gson.fromJson(body, type); } }
40. Login Fragment ApiManager GsonParser Registration Fragment Home Fragment Home Activity Base Activity Auth Activity Api Service Parser Home Listener Registration Listener Login Listener
41. public class ApiManager implements ApiService { Parser parser = new GsonParser(); ... }
42. Use dependency injection
43. class ApiManager implements ApiService { Parser parser; public ApiManager(Parser parser){ this.parser = parser; } } public class AuthActivity extends Activity { ApiService apiService = new ApiManager(new GsonParser); void login(){ apiService.login(callback); } }
44. Login Fragment Auth Activity Login Listener Notify user name text changes
45. public interface LoginListener { void onLogin(); void onRegister(); void onUsernameTextChanged(); } public class AuthActivity extends BaseActivity implements LoginListener { @Override public void onLogin(){} @Override public void onRegister(){} @Override public void onUsernameTextChanged() { showToastMessage(); } }
46. public class AccountActivity extends BaseActivity implements LoginListener { @Override public void onLogin(){} @Override public void onRegister(){} @Override public void onUsernameTextChanged() { } }
47. Interface Segregation No method should be forced to implement if it is not used.
48. Split the interface
49. class LoginFragment extends Fragment { TextListener textListener; void setTextListener(TextListener listener) { textListener = listener; } public interface LoginListener { void onLogin(); void onRegister(); } public interface TextListener { void onUsernameTextChanged(); } } class AccountActivity extends Activity implements LoginFragment.LoginListener, LoginFragment.TextListener { public void displayLogin() { LoginFragment f = new LoginFragment(); f.setTextListener(this); ... } @Override public void onLogin(){} @Override public void onRegister(){} @Override public void onUsernameTextChanged(){} }
50. Keys of key-value pair
51. public class HomeActivity extends Activity { private static final String KEY_USER = "KEY_USER"; void something() { intent.putExtra(KEY_USER, user); } } public class HomeFragment extends Fragment { private static final String KEY_USER = "KEY_USER"; void something() { User user = intent.getParcelableExtra(KEY_USER); } } Create the same keys in each class
52. public class HomeActivity extends Activity { public static final String KEY_USER = "KEY_USER"; void something() { intent.putExtra(KEY_USER, user); } } public class HomeFragment extends Fragment { void something() { User user = intent.getParcelableExtra(HomeActivity.KEY_USER); } } Make the keys public
53. public class Constants { public static final String KEY_USER = "KEY_USER"; } public class HomeActivity extends Activity { void something() { intent.putExtra(Constants.KEY_USER, user); } } public class HomeFragment extends Fragment { void something() { User user = intent.getParcelableExtra(Constants.KEY_USER); } } Put all keys to a class
54. Consider static factory method
55. public class HomeActivity extends Activity { private static final String KEY_USER = "KEY_USER"; public static Intent newIntent(Context context, User user) { Intent intent = new Intent(context, HomeActivity.class); intent.putExtra(KEY_USER, user); return intent; } @Override public void onCreate(Bundle bundle) { User user = getIntent().getParcelableExtra(KEY_USER); } } public class LoginActivity extends Activity { void displayHome() { startActivity( HomeActivity.newIntent(this, user); ); } void displayLogin() { … LoginFragment.newFragment(foo); } }
56. public class User { private Account account; public Account getAccount(){ return account; } } public class Account { private Image image; private Credentials credentials; public Image getImage(){ return image; } public Credentials getCredentials() { return credentials; } } public MainActivity { User user; private void initAvatar() { Image image = user.getAccount().getImage(); } }
57. • Each unit should only talk to its friends • Don't talk to strangers. Law of Demeter
58. class User { private final Account account; public Image getAvatar(){ if (account == null){ return null; } return account.getImage(); } } public MainActivity extends Activity { User user; private void initAvatar() { Image image = user.getAvatar(); } }
59. Single Responsibility Liskov’s Substitution Interface Segregation Open/Closed Dependency Inversion Dependency Injection Composite High Cohesion Loose Coupling Static Factory Method Law of Demeter
60. THANK YOU github: github.com/orhanobut twitter: @orhanobut