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Journey to 99% Crash Free Fumihiko Shiroyama

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Slide URL • https://goo.gl/zwxdyy

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About Me • Fumihiko Shiroyama • Android App Developer • Nikkei Inc. • https://github.com/srym • https://twitter.com/fushiroyama

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Agenda • Face up to the reality of crash! • Take the first step for Unit Testing • Make biggest gains without Unit Testing

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The Fact Your App is Crashing

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The Fact Your App is Crashing • 99% Crash Free? Good! • DAU 30000

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The Fact Your App is Crashing • 99% Crash Free? Good! • DAU 30000 $SBTIFT

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The Fact Your App is Crashing • 99% Crash Free? Good! • DAU 30000 • 99.9% Crash Free? Great!!

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The Fact Your App is Crashing • 99% Crash Free? Good! • DAU 30000 • 99.9% Crash Free? Great!! 4UJMM$SBTIFT

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Keep Going!!!

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Fabric • Crashlytics • Beta • Answers • Acquired by Google

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"41MVHJO

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Crashlytics • Automatically collects crash info • No need for uploading obfuscation mappings • Crashlytics#logException(e) for non-fatal

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Crashlytics private void logUser() { // info about user Crashlytics.setUserIdentifier("12345"); Crashlytics.setUserEmail("user@fabric.io"); Crashlytics.setUserName("Test User"); }

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Crashlytics private void logUser() { // info about user Crashlytics.setUserIdentifier("12345"); Crashlytics.setUserEmail("user@fabric.io"); Crashlytics.setUserName("Test User"); }

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Firebase Crash Reporting • Similar to Crashlytics

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"41MVHJO

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Crash Reporting • Automatically collects crash info as well • Need for uploading obfuscation mappings (there is a helper gradle plugin) • FirebaseCrash.report(e) for non-fatal

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Crash Reporting Normal Stack Trace

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Crash Reporting Device Info

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Crash Reporting Contextual History

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Crash Reporting Contextual History $00- &WFOU -PH

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Integration

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Timber dependencies { compile 'com.jakewharton.timber:timber:4.5.1' }

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Timber dependencies { compile 'com.jakewharton.timber:timber:4.5.1' } #FUUFS-PHE

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Timber public class CrashReportingTree extends Timber.Tree { @Override protected void log(int priority, String tag, String message, Throwable t) { if (priority == Log.VERBOSE || priority == Log.DEBUG || priority == Log.INFO) { return; } if (t != null) { Crashlytics.logException(t); FirebaseCrash.report(t); } } }

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Timber public class CrashReportingTree extends Timber.Tree { @Override protected void log(int priority, String tag, String message, Throwable t) { if (priority == Log.VERBOSE || priority == Log.DEBUG || priority == Log.INFO) { return; } if (t != null) { Crashlytics.logException(t); FirebaseCrash.report(t); } } }

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Timber public class CrashReportingTree extends Timber.Tree { @Override protected void log(int priority, String tag, String message, Throwable t) { if (priority == Log.VERBOSE || priority == Log.DEBUG || priority == Log.INFO) { return; } if (t != null) { Crashlytics.logException(t); FirebaseCrash.report(t); } } }

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Timber public class CrashReportingTree extends Timber.Tree { @Override protected void log(int priority, String tag, String message, Throwable t) { if (priority == Log.VERBOSE || priority == Log.DEBUG || priority == Log.INFO) { return; } if (t != null) { Crashlytics.logException(t); FirebaseCrash.report(t); } } } /PO'BUBM

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Timber public class MyApplication extends Application { @Override public void onCreate() { super.onCreate(); initTimber(); } private void initTimber() { if (BuildConfig.DEBUG) { Timber.plant(new Timber.DebugTree()); } else { Timber.plant(new CrashReportingTree()); } } }

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Timber public class MyApplication extends Application { @Override public void onCreate() { super.onCreate(); initTimber(); } private void initTimber() { if (BuildConfig.DEBUG) { Timber.plant(new Timber.DebugTree()); } else { Timber.plant(new CrashReportingTree()); } } }

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Timber public class MyApplication extends Application { @Override public void onCreate() { super.onCreate(); initTimber(); } private void initTimber() { if (BuildConfig.DEBUG) { Timber.plant(new Timber.DebugTree()); } else { Timber.plant(new CrashReportingTree()); } } }

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Timber Timber.d("log message"); // or Timber.e(error, error.getMessage());

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Take the first step for Unit Testing

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Why can't you write test?

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Typical Case

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Fat Activity @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { User user = fetchUser(userId); processUser(user); } }); }

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Fat Activity @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { User user = fetchUser(userId); processUser(user); } }); }

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Fat Activity @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { User user = fetchUser(userId); processUser(user); } }); }

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Typical Case private User fetchUser(long userId) { return apiClient.findUserById(userId); }

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Typical Case private User fetchUser(long userId) { return apiClient.findUserById(userId); } pFMEBDDFTT

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How do I test MyActivity#fetchUser ?

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That's impossible

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Make it testable private User fetchUser(long userId) { return apiClient.findUserById(userId); }

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Make it testable private User fetchUser(ApiClient apiClient, long userId) { return apiClient.findUserById(userId); }

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private User fetchUser(ApiClient apiClient, long userId) { return apiClient.findUserById(userId); } 3FNPWFE pFMEBDDFTT Make it testable

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private User fetchUser(ApiClient apiClient, long userId) { return apiClient.findUserById(userId); } Make it testable

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public class UserFetcher { private User fetchUser(ApiClient apiClient, long userId) { return apiClient.findUserById(userId); } } Make it testable

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public class UserFetcher { public User fetchUser(ApiClient apiClient, long userId) { return apiClient.findUserById(userId); } } Make it testable

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public class UserFetcher { private final ApiClient apiClient; public UserFetcher(ApiClient apiClient) { this.apiClient = apiClient; } public User fetchUser(long userId) { return apiClient.findUserById(userId); } } Make it testable

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public class UserFetcher { private final ApiClient apiClient; public UserFetcher(ApiClient apiClient) { this.apiClient = apiClient; } public User fetchUser(long userId) { return apiClient.findUserById(userId); } } Make it testable

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Make it testable • This is so-called Dependency Injection • DI can be done without any libraries! • You can use DI library at any time though

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Anything else?

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Problem is Activity

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Everything is in Activity @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { User user = fetchUser(userId); processUser(user); } }); }

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Let's split this into parts!

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MVP

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What is MVP • Model - View - Presenter • View…Activity (Fragment) • Model…Business Logic (e.g. fetching data) • Presenter…Bridge between V & M

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Introduce MVP public interface UserContract { public interface View { void showUser(User user); void showError(Exception error); } public interface Interaction { void clickButton(long userId); } }

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Introduce MVP public interface UserContract { public interface View { void showUser(User user); void showError(Exception error); } public interface Interaction { void clickButton(long userId); } } $POUSBDUCFUXFFO 7JFXBOE1SFTFOUFS

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Introduce MVP public interface UserContract { public interface View { void showUser(User user); void showError(Exception error); } public interface Interaction { void clickButton(long userId); } }

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Introduce MVP public interface UserContract { public interface View { void showUser(User user); void showError(Exception error); } public interface Interaction { void clickButton(long userId); } } $BMMCBDLGSPN 1SFTFOUFS

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Introduce MVP public interface UserContract { public interface View { void showUser(User user); void showError(Exception error); } public interface Interaction { void clickButton(long userId); } }

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Introduce MVP public interface UserContract { public interface View { void showUser(User user); void showError(Exception error); } public interface Interaction { void clickButton(long userId); } } &WFOUGSPN 6*

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Introduce MVP public class UserPresenter implements UserContract.Interaction { private final UserContract.View view; private final UserFetcher userFetcher; public UserPresenter(UserContract.View view, UserFetcher userFetcher) { this.view = view; this.userFetcher = userFetcher; } @Override public void clickButton(long userId) { } }

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Introduce MVP public class UserPresenter implements UserContract.Interaction { private final UserContract.View view; private final UserFetcher userFetcher; public UserPresenter(UserContract.View view, UserFetcher userFetcher) { this.view = view; this.userFetcher = userFetcher; } @Override public void clickButton(long userId) { } }

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Introduce MVP public class UserPresenter implements UserContract.Interaction { private final UserContract.View view; private final UserFetcher userFetcher; public UserPresenter(UserContract.View view, UserFetcher userFetcher) { this.view = view; this.userFetcher = userFetcher; } @Override public void clickButton(long userId) { } }

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Introduce MVP @Override public void clickButton(long userId) { userFetcher.findUserAsync(userId, new UserFetcher.OnSuccessCallback() { @Override public void onSuccess(User user) { view.showUser(user); } }, new UserFetcher.OnFailureCallback() { @Override public void onFailure(Exception e) { view.showError(e); } }); }

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Introduce MVP @Override public void clickButton(long userId) { userFetcher.findUserAsync(userId, new UserFetcher.OnSuccessCallback() { @Override public void onSuccess(User user) { view.showUser(user); } }, new UserFetcher.OnFailureCallback() { @Override public void onFailure(Exception e) { view.showError(e); } }); }

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Introduce MVP @Override public void clickButton(long userId) { userFetcher.findUserAsync(userId, new UserFetcher.OnSuccessCallback() { @Override public void onSuccess(User user) { view.showUser(user); } }, new UserFetcher.OnFailureCallback() { @Override public void onFailure(Exception e) { view.showError(e); } }); }

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Introduce MVP public class MyActivity extends BaseActivity implements UserContract.View { @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); } @Override public void showUser(User user) {} @Override public void showError(Exception error) {} }

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Introduce MVP public class MyActivity extends BaseActivity implements UserContract.View { @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); } @Override public void showUser(User user) {} @Override public void showError(Exception error) {} }

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Introduce MVP @Override protected void onCreate(@Nullable Bundle savedInstanceState) { final UserPresenter presenter = new UserPresenter(this, userFetcher); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { presenter.clickButton(userId); } }); } @Override public void showUser(User user) { toastMessage(user.getName()); } @Override public void showError(Exception e) { toastMessage(e()); } }

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Introduce MVP @Override protected void onCreate(@Nullable Bundle savedInstanceState) { final UserPresenter presenter = new UserPresenter(this, userFetcher); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { presenter.clickButton(userId); } }); } @Override public void showUser(User user) { toastMessage(user.getName()); } @Override public void showError(Exception e) { toastMessage(e()); } }

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Introduce MVP @Override protected void onCreate(@Nullable Bundle savedInstanceState) { final UserPresenter presenter = new UserPresenter(this, userFetcher); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { presenter.clickButton(userId); } }); } @Override public void showUser(User user) { toastMessage(user.getName()); } @Override public void showError(Exception e) { toastMessage(e()); } }

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Introduce MVP @Override protected void onCreate(@Nullable Bundle savedInstanceState) { final UserPresenter presenter = new UserPresenter(this, userFetcher); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { presenter.clickButton(userId); } }); } @Override public void showUser(User user) { toastMessage(user.getName()); } @Override public void showError(Exception e) { toastMessage(e()); } }

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Result • Now objects' responsibilities are clearer • Dependency is provided at constructor • Thus testable!

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Make biggest gains without Unit Testing

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It turned out...

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Quite a few crashes were caused by...

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IllegalStateException java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState

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IllegalStateException java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState 'SBHNFOU5SBOTBDUJPODPNNJU

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FragmentTransaction • FragmentTransaction#commit • DialogFragment#show

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FragmentTransaction public void show(FragmentManager manager, String tag) { mDismissed = false; mShownByMe = true; FragmentTransaction ft = manager.beginTransaction(); ft.add(this, tag); ft.commit(); }

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FragmentTransaction public void show(FragmentManager manager, String tag) { mDismissed = false; mShownByMe = true; FragmentTransaction ft = manager.beginTransaction(); ft.add(this, tag); ft.commit(); }

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Don't commit after... • AsyncTask#onPostExecute • LoaderCallbacks#onLoadFinished • Actually ANY KINDS OF ASYNC CALLBACKS are not safe

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RxLifecycle?

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RxLifecycle • RxLifecycle IS GREAT!! • Not all programmers, nor projects always need this. • Vulture is for you!

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Vulture • https://github.com/srym/vulture • Handles async callback safely • Based on PauseHandler* picture from wikimedia.org * https://goo.gl/g6w3CS

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Vulture void fetchAsynchronously() { /* do heavy asynchronous task here */ doCallback("finished!"); } void doCallback(@NonNull String message) { FinishDialog.newInstance().show( getSupportFragmentManager(), "TAG"); }

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Vulture void fetchAsynchronously() { /* do heavy asynchronous task here */ doCallback("finished!"); } void doCallback(@NonNull String message) { FinishDialog.newInstance().show( getSupportFragmentManager(), "TAG"); }

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Vulture void fetchAsynchronously() { /* do heavy asynchronous task here */ doCallback("finished!"); } void doCallback(@NonNull String message) { FinishDialog.newInstance().show( getSupportFragmentManager(), "TAG"); }

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Vulture void fetchAsynchronously() { /* do heavy asynchronous task here */ doCallback("finished!"); } void doCallback(@NonNull String message) { FinishDialog.newInstance().show( getSupportFragmentManager(), "TAG"); } 6OTBGF

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Vulture @ObserveLifecycle public class YourActivity extends AppCompatActivity { void fetchAsynchronously() { SafeMainActivity.doCallbackSafely("finished!"); } @SafeCallback void doCallback(@NonNull String message) { FinishDialog.newInstance().show( getSupportFragmentManager(), "TAG"); } }

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Vulture @ObserveLifecycle public class YourActivity extends AppCompatActivity { void fetchAsynchronously() { SafeMainActivity.doCallbackSafely("finished!"); } @SafeCallback void doCallback(@NonNull String message) { FinishDialog.newInstance().show( getSupportFragmentManager(), "TAG"); } }

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Vulture @ObserveLifecycle public class YourActivity extends AppCompatActivity { void fetchAsynchronously() { SafeMainActivity.doCallbackSafely("finished!"); } @SafeCallback void doCallback(@NonNull String message) { FinishDialog.newInstance().show( getSupportFragmentManager(), "TAG"); } }

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Vulture @Override protected void onResume() { super.onResume(); SafeMainActivity.register(this); } @Override protected void onPause() { SafeMainActivity.unregister(); super.onPause(); }

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Vulture @Override protected void onResume() { super.onResume(); SafeMainActivity.register(this); } @Override protected void onPause() { SafeMainActivity.unregister(); super.onPause(); }

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Supported Types • Primitive types and its boxed types • String, Bundle, Parcelable, Serializable • ParcelableArray • ParcelableArrayList

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Vulture • Currently Beta release • I need your feedbacks! picture from wikimedia.org

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Thank You!

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Special Thanks • Illustrations by ͍Β͢ͱ΍ • http://www.irasutoya.com/ • Thank you so much!!! • https://www.wikimedia.org/ • All the audiences! Thank you!