Crashing is good for your app

As Android devs, we are usually too afraid of the crash. We go way too far to avoid crashing.

Sometimes our motto is no Crash at all costs.

Wrapping all of our java objects in double null checks, Elvis (?:) operators everywhere, absolutely no double bang (!!), "try-catch" everything.

These are just a few samples of what we do to avoid that innocent crash.

I'm here to tell you to stop.
We should let our crashes happen. I'll show you how they are useful and help us build better and safer apps.
Removing all of them does not help our apps or users.

I explain why it's bad to stop crashing at all costs.

Let's crash!!!

Slides with Animations:
https://bit.ly/3nQVbdv

Transcript

1. In the name of God Crashing is good for your app
2. I am Seyed Jafari Software Engineer @ Revolut Ltd worldsnas.com @worldsnas
3. What is a CRASH 💥 Wiki: In computing, a crash, occurs when a software application stops functioning properly and exits. Me: When a program stops working unexpectedly
4. How do they crash? 🤔 • Hardware issues • Galactic rays 🤯 • Software bugs
5. Software bugs Exceptions
6. Exception Techopedia: An exception is an abnormal or unprecedented event that occurs after the execution of a software program or application. It is a runtime error of an undesired result or event affecting normal program flow.
7. Exceptions for exceptionals! When something terribly goes wrong. It’s unacceptable. No way! Does not meet the rules. Simple Example: var result = 1 / 0
8. Famous exceptions/errors we all know 1. NullPointerException 2. IOException 3. OutOfMemoryError 4. StackOverflowError Kotlin/Native InvalidMutabilityException
9. Exceptions Good Bad or
10. Exception driven vs If-Else Effective Java chapter 10, item 69 Elixir
11. Use Cases and how to deal with them
12. fun getBookNames(libraryId : String): Data<Error, List<String>> = try { Data.Success(fetchBookNames(libraryId)) }catch(e : IOException) { Data.Failed(e) } NetworkRequests AwesomeRepository.kt Catching example
13. Enum mappings Good Exceptions enum class LightSwitchState{ ON, OFF, UNKNOWN, } fun mapStateToEnum(state : String): LightSwitchState = LightSwitchState .values() .find { it.name == state } ?: UNKNOWN
14. Enum mappings Good Exceptions enum class LightSwitchState{ ON, OFF, } fun mapStateToEnum(state : String): LightSwitchState? = LightSwitchState .values() .find { it.name == state }
15. Enum mappings Good Exceptions enum class LightSwitchState{ ON, OFF, } fun mapStateToEnum(state : String): LightSwitchState = LightSwitchState .values() .first { it.name == state }
16. var binding: FragmentAwesomeBinding? = null ViewBinding vs Fragments AwesomeFragment.kt Good Exceptions fun setTitle(txt : String) { binding?.title.text = txt }
17. var _binding: FragmentAwesomeBinding? = null val binding get() = _binding!! fun onViewCreated(view: View) { _binding = FragmentAwesomeBinding.bind(view) } fun onViewDestroyed(view: View){ _binding = null } fun setTitle(txt : String) { binding.title.text = txt } ViewBinding vs Fragments AwesomeFragment.kt Good Exceptions
18. Good Exceptions var _binding: FragmentAwesomeBinding? = null val binding get() = _binding!! fun onViewCreated(view: View) { _binding = FragmentAwesomeBinding.bind(view) } fun onViewDestroyed(view: View){ _binding = null } fun setTitle(txt : String) { binding.title.text = txt } ViewBinding vs Fragments AwesomeFragment.kt
19. var _binding: FragmentAwesomeBinding? = null val binding get() = _binding!! fun onViewCreated(view: View) { _binding = FragmentAwesomeBinding.bind(view) } fun onViewDestroyed(view: View){ _binding = null } fun setTitle(txt : String) { binding.title.text = txt } ViewBinding vs Fragments AwesomeFragment.kt Good Exceptions
20. Good Exceptions Business logics and specs fun packThreeBooks(books : List<Book>): BookPack { require(books.size == 3){ "we need exactly three books to pack" } return packageBooks(books) }
21. Catching exceptions Safe layering the good exceptions fun getBooksAndPackThem(library : Library) : BookPack? { val books = library.getBooks() return try{ packThreeBooks(books) }catch(e: Exception){ null } }
22. Try-catch Let them pass vs
23. BUT
24. Exception vs UX
25. Exception is bad for UX, Let’s Fix it 1. Try-Catch everything 2. Add Safe Layers 3. Set Thread Uncaught Exception handlers We are safe now!
26. Are we really “safe“ now?
27. UX in “Safe” mode fun enablePayBtn() { binding?.payBtn.isEnabled = true } Users: Still not fixed
28. Let it crash fun enablePayBtn() { binding.payBtn.isEnabled = true } Users: Fixed immediately
29. Still not convinced? 😲 Another example...
30. I hear you, skepticals! Logging
31. Exception Logging vs
32. I/Fitness: OnPackageChangedOperation got intent: Intent... I/Icing: Indexing com.google.android.gms-apps from com.google.android.gms [CONTEXT service_id=21 ] I/Icing: Indexing done com.google.android.gms-apps [CONTEXT service_id=21 ] I/Telecom: DefaultDialerCache: Refreshing default dialer for user 0: now com.android.dialer: DDC.oR@AI8 I/system_server: Background young concurrent copying GC freed 80900(4601KB) AllocSpace objects, 11(1124KB) LOS objects, 11% free, 31MB/35MB, paused 458us total 142.940ms I/CarrierSvcBindHelper: No carrier app for: 0 I/Fitness: FitCleanupIntentOperation received Intent android.intent.action.PACKAGE_CHANGED I/Fitness: OnPackageChangedOperation got intent: Intent... I/Icing: Indexing com.google.android.gms-apps from com.google.android.gms [CONTEXT service_id=21 ] I/Icing: Indexing done com.google.android.gms-apps [CONTEXT service_id=21 ] I/Fitness: FitCleanupIntentOperation received Intent android.intent.action.PACKAGE_CHANGED Logging issues Dear Logcat indistinct
33. I/Fitness: OnPackageChangedOperation got intent: Intent... I/Icing: Indexing com.google.android.gms-apps from com.google.android.gms [CONTEXT service_id=21 ] I/Icing: Indexing done com.google.android.gms-apps [CONTEXT service_id=21 ] I/Telecom: DefaultDialerCache: Refreshing default dialer for user 0: now com.android.dialer: DDC.oR@AI8 I/system_server: Background young concurrent copying GC freed 80900(4601KB) AllocSpace objects, 11(1124KB) LOS objects, 11% free, 31MB/35MB, paused 458us total 142.940ms I/CarrierSvcBindHelper: No carrier app for: 0 I/Fitness: FitCleanupIntentOperation received Intent android.intent.action.PACKAGE_CHANGED I/Fitness: OnPackageChangedOperation got intent: Intent... I/Icing: Indexing com.google.android.gms-apps from com.google.android.gms [CONTEXT service_id=21 ] I/Icing: Indexing done com.google.android.gms-apps [CONTEXT service_id=21 ] I/Fitness: FitCleanupIntentOperation received Intent android.intent.action.PACKAGE_CHANGED Logging issues Dear Logcat indistinct
34. java.lang.OutOfMemoryError at android.graphics.BitmapFactory.nativeDecodeAsset(Native Method) at android.graphics.BitmapFactory.decodeStream(BitmapFactory.java:683) at android.graphics.BitmapFactory.decodeResourceStream(BitmapFactory.java:513) at android.graphics.drawable.Drawable.createFromResourceStream(Drawable.java:889) at android.content.res.Resources.loadDrawable(Resources.java:3436) at android.content.res.Resources.getDrawable(Resources.java:1909) at android.view.View.setBackgroundResource(View.java:16251) at com.autkusoytas.bilbakalim.SoruEkrani.cevapSecimi(SoruEkrani.java:666) at com.autkusoytas.bilbakalim.SoruEkrani$9$1.run(SoruEkrani.java:862) at android.os.Handler.handleCallback(Handler.java:733) ….. Exceptions advantage Dear Logcat Easily distinguishable
35. • V: Verbose. • D: Debug. • I: Info. • W: Warning. • E: Error. • A: Assert. Logging issues Android SDK Hard to choose
36. Exceptions advantage Java std throwables Clear types • java.lang.NullPointerException • java.io.IOException • java.lang.IllegalStateException • java.lang.IllegalArgumentException • java.lang.OutOfMemoryError • java.lang.StackOverflowError
37. tag= MainActivity::class.simpleName, msg= "some f… thing went wrong", tr= null Logging issues Logcat.d Manual INFO gathering ) Log.d(
38. Exceptions advantage IllegalArgumentException() Automatic Info attaching • No tags needed • StackTrace • Name is a good enough message
39. • Checking logs regularly (usually ignored) • Finding the right one (find a needle in a haystack) • Setting severity level • Assigning to the right team • Velocity Alerts Logging issues Slow & Hard Addersing
40. Exceptions advantage Fast & Easy Addersing • They are highly prioritised (fixed even during weekends! 󰣻) • Usually delivered to devs inbox • They can be assigned automatically • Types can be used as Severity • Alerts already set (Crashlytics)
41. • Firebase Events Logging issues Custom vs Paid options Reporting tool
42. Exceptions advantage Exception reporting services Most of the services are free • Crashlytics • Sentry • Yandex • Bugsnag
43. Logs Are good and useful Not a replacement for Exceptions
44. Exceptions Good Bad or It depends
45. 💥 Happy Crashing 💥 @worldsnas Reach out to me about your crashes 🤗 Thanks We are actively hiring in wide range of positions. make sure to checkout our openings on: https://www.revolut.com/careers