Trying to implement the same functionality on Android on different devices, OS versions, manufacturers etc. can be more eventful than it should. This presentation is a guide about how you can achieve your task at hand without compromising code quality and readability. Specifically, I demonstrate how to use Dependency Injection, the MVP pattern and other techniques to your favour, for graceful handling and degrading experience at production code and automated tests.

1. Device Fragmentation
Clean Code
Iordanis “Jordan” Giannakakis
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2. Introduction
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Iordanis “Jordan” Giannakakis
Android Team Lead – Shazam
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3. How Shazam works
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4. Bad vs. good code
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5. How is fragmentation related to
clean code?
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6. Is fragmentation really a problem?
android.support
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7. Is fragmentation really a problem?
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8. Is clean code really a concern?
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9. Is clean code really a concern?
A couple of months later...
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10. SharedPreferences.Editor
• commit() – slow
• apply() – fast
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11. API example – MainActivity
protected void onResume() {
super.onResume();
SharedPreferences sharedPreferences =
PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = sharedPreferences.edit();
prefEditor.putBoolean("has_launched_before", true);
// Will only be available for versions after Froyo
if(VERSION.SDK_INT >= VERSION_CODES.GINGERBREAD) {
editor.apply();
} else {
editor.commit();
}
}
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12. Fixed it!
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13. What are the issues?
protected void onResume() {
super.onResume();
SharedPreferences sharedPreferences =
Glue
PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = sharedPreferences.edit();
Business
prefEditor.putBoolean("has_launched_before", true);
Logic
// Will only be available for versions after Froyo
if(VERSION.SDK_INT >= VERSION_CODES.GINGERBREAD) {
editor.apply();
} else {
editor.commit();
}
Glue
}
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14. How to unit test?
Good luck!
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15. Dependency Injection
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16. Dependency Injection Framework
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17. New MainActivity
@Override
public void onResume() {
super.onResume();
editor.putBoolean("has_launched_before", true);
preferencesSaver.save(editor);
}
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18. Before & After
protected void onResume() {
super.onResume();
SharedPreferences sharedPreferences =
PreferenceManager
.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor =
sharedPreferences.edit();
prefEditor.putBoolean(
"has_launched_before", true);
// Will only be available for versions
after Froyo
if(VERSION.SDK_INT >=
VERSION_CODES.GINGERBREAD) {
editor.apply();
} else {
editor.commit();
}
}
public void onResume() {
super.onResume();
editor.putBoolean(
"has_launched_before", true);
preferencesSaver.save(editor);
}
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19. New MainActivity – Constructors
// Constructor the system will call to instantiate this activity
public MainActivity() {
this(sharedPreferencesEditor(), preferencesSaver());
}
// Constructor that can be used in production and test code
public MainActivity(Editor editor, PreferencesSaver preferencesSaver) {
this.editor = editor;
this.preferencesSaver = preferencesSaver;
}
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20. Module classes
public class SharedPreferencesEditorModule {
public static SharedPreferences.Editor sharedPreferencesEditor() {
Context context = getApplication().getApplicationContext();
SharedPreferences preferences = getDefaultSharedPreferences(context);
Editor editor = preferences.edit();
return editor;
}
}
public class PreferencesSaverModule {
public static PreferencesSaver preferencesSaver() {
if(VERSION.SDK_INT >= VERSION_CODES.GINGERBREAD) {
return new ApplyPreferencesSaver();
}
return new CommitPreferencesSaver();
}
}
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21. Application
public class MyCoolApplication extends Application {
private static MyCoolApplication application;
@Override
public void onCreate() {
application = this;
}
public static MyCoolApplication getApplication() {
return application;
}
}
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22. How to unit test?
@Mock Editor editor;
@Mock PreferencesSaver saver;
@Test
public void canSaveLaunchFlag() {
mockery.checking(new Expectations() {{
atLeast(1).of(editor).putBoolean("has_launched_before", true);
oneOf(saver).save(editor);
}});
MainActivity activity = new MainActivity(editor, saver);
activity.onResume();
}
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23. Capabilities example – Google+
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24. Capabilities example
public void onCreate(Bundle savedInstanceState) {
// Set layout
View googlePlus = findViewById(R.id.google_plus);
try {
getPackageManager().getApplicationInfo("com.android.vending", 0);
googlePlus.setVisibility(VISIBLE);
} catch (PackageManager.NameNotFoundException e) {
googlePlus.setVisibility(GONE);
}
}
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25. MVP pattern
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26. The Model
public class GooglePlayAvailability {
private PackageManager packageManager;
public GooglePlayAvailability(PackageManager packageManager) {
this.packageManager = packageManager;
}
public boolean googlePlayIsAvailable() {
try {
packageManager.getApplicationInfo("com.android.vending", 0);
return true;
} catch (PackageManager.NameNotFoundException e) {
return false;
}
}
}
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27. The View
public interface GooglePlusView {
public void showGooglePlus();
public void hideGooglePlus();
}
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28. Activity as View
public class MainActivity extends Activity implements GooglePlusView {
public void onCreate(Bundle savedInstanceState) {
//Set layout...
googlePlus = findViewById(R.id.google_plus);
//Injected googlePlusPresenter
googlePlusPresenter.setView(this);
googlePlusPresenter.present();
}
public void showGooglePlus() {
googlePlus.setVisibility(VISIBLE);
}
public void hideGooglePlus() {
googlePlus.setVisibility(GONE);
}
}
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29. The Presenter
public class GooglePlusPresenter {
private GooglePlayAvailability googlePlayAvailability;
private GooglePlusView googlePlusView;
public GooglePlusPresenter(GooglePlayAvailability availability) {
googlePlayAvailability = availability;
}
public void present() {
if (googlePlayAvailability.googlePlayIsAvailable()) {
googlePlusView.showGooglePlus();
} else {
googlePlusView.hideGooglePlus();
}
}
}
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30. How to unit test?
@Mock GooglePlayAvailability googlePlayAvailability;
@Mock GooglePlusView googlePlus;
private GooglePlusPresenter presenter;
@Test
public void hidesGooglePlusIfNotAvailable() {
mockery.checking(new Expectations() {{
allowing(googlePlayAvailability).googlePlayIsAvailable();
will(returnValue(false));
oneOf(googlePlus).hideGooglePlus();
}});
presenter.present();
}
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31. Device size diversity
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32. Device size diversity
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33. How about Acceptance Tests?
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34. How about Acceptance Tests?
public class ShazamTest extends
ActivityInstrumentationTestCase2<ActivityUnderTest> {
private static final int TIMEOUT = 5000;
private Solo solo;
protected void setUp() {
solo = new Solo(getInstrumentation());
}
}
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35. How about Acceptance Tests?
public void testCanShazamOnPhone() {
// Action
// User hits the big Shazam button
View shazamButton = solo.getView(R.id.big_button);
solo.clickOnView(shazamButton);
// Assertions
// Track details are showing on full screen
assertThat(solo.waitForCondition(titleShowsOnFullScreen(),
TIMEOUT), is(true));
}
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36. How about Acceptance Tests?
public void testShazamingOnTablet() {
// Action
// Hit small Shazam button and wait for animation to finish
final View shazamButton = solo.getView(R.id.small_button);
solo.clickOnView(shazamButton);
waitForAnimationToFinish();
// Assertions
// Track details are showing on side-panel
assertThat(solo.waitForCondition(titleShowsOnSidePanel(),
TIMEOUT), is(true));
}
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37. Fixed it!
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38. Test frameworks
GWEN
https://github.com/shazam/gwen
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39. New Acceptance Test
protected void setUp() {
solo = new Solo(getInstrumentation());
user = new User(solo);
}
public void testCanShowTrackAfterShazaming() {
when(user).shazams();
then(user).seesDetailsForTrack();
}
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40. User class
public class User implements Actor, Asserter {
private final Solo solo;
public void shazams() {
Action<Solo, Void> action;
if (isTablet()) {
action = new ShazamTabletButtonAction();
} else {
action = new ShazamPhoneButtonAction();
}
action.actOn(solo);
}
public void seesDetailsForTrack() {
Assertion<Solo> assertion;
if (isTablet()) {
assertion = new TabletDetailsAssertion();
} else {
assertion = new PhoneDetailsAssertion();
}
assertion.assertWith(solo);
}
}
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41. Actions
public class ShazamPhoneButtonAction implements Action<Solo, Void> {
public void actOn(Solo solo) {
View bigButton = solo.getView(R.id.big_button);
solo.clickOnView(bigButton);
}
}
public class ShazamTabletButtonAction implements Action<Solo, Void> {
public void actOn(Solo solo) {
View smallButton = solo.getView(R.id.small_button);
solo.clickOnView(smallButton);
}
}
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42. Assertions
public class PhoneDetailsAssertion implements Assertion<Solo>{
public void assertWith(Solo solo) {
assertThat(solo.waitForCondition(titleShowsOnFullScreen(),
TIMEOUT), is(true));
}
}
public class TabletDetailsAssertion implements Assertion<Solo> {
public void assertWith(Solo solo) {
waitForAnimationToFinish();
assertThat(solo.waitForCondition(titleShowsOnSidePanel(),
TIMEOUT), is(true));
}
}
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43. Fixed it!
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44. Hiring...
Questions?
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github.com/iordanis/androidCleanCode