Mobile App Debugging

Overview

Mobile app debugging addresses platform-specific issues, device hardware limitations, and mobile-specific network conditions.

When to Use

• App crashes on mobile

• Performance issues on device

• Platform-specific bugs

• Network connectivity issues

• Device-specific problems

Instructions

1. iOS Debugging

Xcode Debugging:

Attach Debugger:

• Xcode → Run on device
• Set breakpoints in code
• Step through execution
• View variables
• Console logs

View Logs:

• Xcode → Window → Devices & Simulators
• Select device → View Device Logs
• Filter by app name
• Check system logs for crashes

Inspect Memory:

• Xcode → Debug → View Memory Graph
• Identify retain cycles
• Check object count
• Monitor allocation growth

Common iOS Issues:

App Crash (SIGABRT): Cause: Exception in Objective-C Solution: Check console for error message Debug: Set breakpoint on exception

Memory Warning (SIGKILL): Cause: Too much memory usage Solution: Reduce memory footprint Optimize: Image caching, data structures

Networking: Issue: Network requests fail on device Check: Network connectivity status Solution: Implement Network Link Conditioner Test: Throttle network in Xcode

2. Android Debugging

Android Studio:

Attach Debugger:

• Run → Debug
• Set breakpoints
• Step through code
• Watch variables
• Evaluate expressions

Logcat:

• Displays all app logs
• Filter by tag
• Filter by process
• Show errors and warnings

Device Monitor:

• Memory profiler
• CPU profiler
• Network profiler
• Battery usage

Common Android Issues:

App Crash (ANR): Cause: Long-running operation on main thread Solution: Move to background thread Example: Use AsyncTask or coroutines

Memory Leak: Cause: Activity not garbage collected Solution: Clear references in onDestroy Debug: Android Profiler shows retained objects

Networking: Issue: Network requests timeout Check: Network connectivity Solution: Implement timeout and retry Test: Simulate poor network

3. Cross-Platform Issues

React Native Debugging:

Console Logs:

• Run app with: react-native run-android
• View logs: adb logcat | grep ReactNativeJS
• Or use remote debugger

Remote Debugging:

• Shake device → Enable Remote Debugging
• Chrome DevTools debugging
• Set breakpoints in JS
• Inspect state

Performance:

• Perf Monitor: Shake → Perf Monitor
• Shows FPS, RAM, Bridge traffic
• Identify frame drops
• Check excessive bridge calls

Flutter Debugging:

Device Logs: flutter logs Shows all device and app output

Debugging: flutter run --debug Set breakpoints in IDE Step through code

Hot Reload: Useful for rapid iteration Hot restart for full reload Useful for debugging UI changes

Common Mobile Issues:

Network Connectivity: Issue: App works on WiFi, fails on cellular Solution: Test on both networks Debug: Use network throttler Implement: Retry logic, offline support

Device Specific: Issue: Works on simulator, fails on device Solution: Always test on real device Causes: - Memory constraints - Performance differences - Platform differences - Screen size issues

Battery/Memory: Issue: Excessive battery drain Debug: Use power profiler Optimize: Reduce background work Monitor: Location tracking, networking

4. Mobile Testing & Debugging Checklist

Device Testing:

[ ] Test on both iOS and Android [ ] Test on old and new devices [ ] Test with poor network (3G throttle) [ ] Test in airplane mode [ ] Test with low battery [ ] Test with low memory [ ] Test with location disabled [ ] Test with notifications disabled [ ] Test rotation changes [ ] Test while backgrounded

Performance:

[ ] <16ms per frame (60 FPS) [ ] Memory usage <100MB [ ] Battery drain acceptable [ ] Network requests efficient [ ] Background tasks minimal

Networking:

[ ] Works on WiFi [ ] Works on cellular [ ] Handles network timeouts [ ] Handles offline mode [ ] Retries failed requests [ ] Shows loading indicators [ ] Shows error messages

UI/UX:

[ ] Responsive touch targets (44x44 min) [ ] Readable text (16pt minimum) [ ] Colors accessible [ ] Orientation changes handled [ ] Keyboard shows/hides correctly [ ] Safe areas respected (notches)

Tools:

Testing Devices:

• iOS: iPhone SE (small), iPhone 12/13 (modern)
• Android: Pixel 4 (standard), Pixel 6 (new)
• Virtual: Simulators for iteration

Device Management:

• TestFlight (iOS)
• Google Play Beta (Android)
• Firebase Test Lab
• BrowserStack

Monitoring:

• Crashlytics
• Firebase Analytics
• App Performance Monitoring
• Custom event tracking

Key Points

• Always test on real devices

• Simulate poor network conditions

• Monitor memory and CPU

• Test on old and new devices

• Use platform-specific debugging tools

• Check device logs for crashes

• Test network edge cases

• Monitor battery/memory impact

• Use profilers to identify bottlenecks

• Implement proper error handling