Surviving Mobile Constraints

This is a lightning talk I gave for the “Mobile Lightning” event at Philly Tech Week 2012.

Transcript

1. Surviving Mobile Constraints
2. June 29, 2007 2 Quad Core Processors @ 3.0GHz 1 Single Core Processor @ 412 MHz 1GB - 32GB RAM 128MB RAM Gigabit Ethernet Edge & WiFi Up to 8 2560x1600 Displays One 3½ Inch 320x480 Display
3. Mobile Constraints Limited Memory Slow Processor Battery Life Slow Network Small Screen
4. iOS Beware of Watchdog • Watchdog is a process that ensures apps play nice within these constraints. • It will kill your app if it takes up too many resources. animalsbeingdicks.com
5. Limited Memory Slow Processor Battery Life Slow Network Small Screen
6. Limited Memory • On iOS, there’s no swap file. • 20MB*, you get memory warnings. • 30MB*, watchdog kills your app. *These can vary based on device, apps running, etc…
7. Limited Memory • Always test on the device: • Simulator doesn’t have memory constraints. • Profile memory usage: • “Allocations” instrument on iOS • iOS - Check for memory leaks Test
8. Limited Memory • Cache judiciously: • NSCache on iOS. • getCacheDir() on Android. • Download large files directly to disk: • NSFileHandle on iOS • DownloadManager on Android Tips
9. Limited Memory • Always handle memory warnings: • iOS - didReceiveMemoryWarning. Tips
10. Slow Processor Low Memory Battery Life Slow Network Small Screen
11. Slow Processor • Complex operations will take more time. • Long operations can block the UI. • iOS - Watchdog will kill an app if it blocks the main thread for > 30 seconds. • Exception: 0x8badf00d (ate bad food).
12. Slow Processor • Test on Device: • iOS - Simulator will run at native processor speed. • Profile slow code: • iOS - “Timer Profiler” instrument. • View methods by time how long they take. Test
13. Slow Processor • Familiarize yourself with concurrency: • iOS - NSOperation. • iOS - Grand Central Dispatch. • Android - AsyncTask. • Both Android and iOS have specific threads that UI updates must be called on. Tips
14. Battery Life Low Memory Slow Processor Slow Network Small Screen
15. Battery Life
16. Battery Life • This is a major issue with many factors: • CPU/GPU usage. • Antennas: Cellular, WiFi, GPS, Bluetooth. • Screen Brightness. • etc…
17. Battery Life • iOS - You can test this! • Profile with the “Energy Diagnostics” instrument. • Always profile while on battery power! • See “Instruments User Guide” for more details Test
18. Battery Life Test
19. Slow Network Low Memory Slow Processor Small Screen Battery Life
20. Slow Network • User may have a super slow network connection. • User may not even have a network connection. • User may often often lose connection. • Most users may have a cellular data cap!
21. Slow Network • Hard to test all network situations. • Do real world testing as much as possible. • iOS - Network Link Conditioner system preference can simulate different network conditions. Test
22. Slow Network • Don’t assume anything about the network connection. • Fail Gracefully. It will fail for someone. • Avoid UI blocking networking: • iOS - sendSynchronousRequest Tips
23. Small Screen Low Memory Slow Processor Slow Network Battery Life
24. Small Screen • Expect screens between 3½ and 5 inches. • Fingers are larger and less precise than mice: • iOS - 44 square points recommended for controls.
25. Small Screen • Always do user testing. • User may interact through accessibility controls: • Test these too! Test
26. Small Screen • Re-prioritize what is important & keep only what is needed. • Minimize screen space used for branding or unnecessary elements. • Grouping & hierarchy become very important: • iOS - UINavigationController Tips
27. Small Screen • Hide controls when they’re not needed • Find interesting uses for gestures • Scrolling and panning is fun. Take advantage of it. (e.g. Twitter) Tips
28. Mobile Constraints Limited Memory Slow Processor Battery Life Slow Network Small Screen
29. Embrace these Constraints
30. Why? “…more iOS devices were sold in 2011… than all the Macs ever sold” - asymco.com “There are more Android activations every day than babies born on earth” - Robert Kyncl, YouTube
31. Why? Mobile is popular! It is just beginning to bloom. It is leading innovation… despite these constraints.
32. Why? …or because of them?
33. Why? “Necessity is the mother of all invention.”
34. @mthomas Matt Thomas codecaffeine.com