Android Debug

Android App Debugging Skill

Expert guidance for debugging Android Flutter applications, covering runtime errors, build issues, device connectivity, and performance problems.

When to Use This Skill

• App crashes or runtime errors on Android
• Build failures in Android-specific code
• Device/emulator connection issues
• Performance problems (lag, memory, battery)
• Platform channel issues
• Native Android integration bugs
• APK/App Bundle generation problems

Debugging Workflow

1. Identify the Problem Type

Runtime Errors: App crashes, exceptions, unexpected behavior Build Errors: Gradle failures, dependency conflicts, compilation errors Device Issues: Cannot connect, not detecting device Performance Issues: Slow UI, memory leaks, battery drain

2. Gather Information

# Check Flutter doctor
flutter doctor -v

# List connected devices
flutter devices

# Run with verbose logging
flutter run --verbose

# Check Android logcat
flutter logs
# Or directly: adb logcat

3. Common Debug Commands

Device Connection

# List connected devices
adb devices

# Restart adb server
adb kill-server
adb start-server

# Connect to device over network
adb connect <device-ip>:5555

# Check device info
adb shell getprop ro.build.version.release

App Debugging

# Install debug APK
flutter install

# Run with debug logging
flutter run -d <device-id> --verbose

# Hot reload
r (in running flutter session)

# Hot restart
R (in running flutter session)

# View performance overlay
P (in running flutter session)

Log Analysis

# Filter logs by app
flutter logs | grep -i "flutter"

# Android-specific logs
adb logcat -s flutter

# Clear logs
adb logcat -c

# Save logs to file
adb logcat > debug.log

4. Common Issues and Solutions

Build Failures

Issue: Gradle build fails

# Clean and rebuild
flutter clean
cd android
./gradlew clean
cd ..
flutter pub get
flutter build apk

Issue: Dependency conflicts

# Check dependencies
cd android
./gradlew app:dependencies

# Update Gradle
cd android
./gradlew wrapper --gradle-version=8.0

Issue: Java version mismatch

# Check Java version (should be 17)
java -version

# Set JAVA_HOME if needed
export JAVA_HOME=/path/to/java17

Runtime Crashes

Issue: App crashes on startup

1. Check logs: flutter logs
2. Look for stack traces
3. Check AndroidManifest.xml permissions
4. Verify minimum SDK version in android/app/build.gradle.kts

Issue: Platform channel errors

1. Verify method names match between Dart and Kotlin/Java
2. Check parameter types are compatible
3. Add null safety checks
4. Review platform-specific code in android/app/src/main/kotlin/

Performance Issues

Issue: UI lag or jank

# Run in profile mode
flutter run --profile

# Enable performance overlay
flutter run --profile --trace-skia

Issue: Memory leaks

1. Use Flutter DevTools Memory tab
2. Check for retained references
3. Dispose controllers properly
4. Review image caching

Issue: Large APK size

# Analyze size
flutter build apk --analyze-size

# Enable R8 shrinking (already enabled in template)
# Check android/app/build.gradle.kts

5. Using Flutter DevTools

# Open DevTools
flutter pub global activate devtools
flutter pub global run devtools

# Or run automatically
flutter run --devtools

DevTools Features:

• Inspector: Widget tree visualization
• Timeline: Performance profiling
• Memory: Heap snapshots and leak detection
• Network: HTTP request monitoring
• Logging: Real-time log viewing
• Debugger: Breakpoints and step debugging

6. Android-Specific Debug Tools

Android Studio

1. Open android/ folder in Android Studio
2. Use Android Profiler for deep analysis
3. Run layout inspector
4. Use APK Analyzer

ADB Commands

# Take screenshot
adb shell screencap /sdcard/screen.png
adb pull /sdcard/screen.png

# Record screen
adb shell screenrecord /sdcard/demo.mp4

# Get app info
adb shell dumpsys package com.cmwen.min_flutter_template

# Force stop app
adb shell am force-stop com.cmwen.min_flutter_template

# Clear app data
adb shell pm clear com.cmwen.min_flutter_template

# Monitor CPU usage
adb shell top | grep flutter

Common Error Patterns

Gradle Errors

• Solution: Clean build, check Java version, update dependencies
• Files to check: android/build.gradle.kts, android/app/build.gradle.kts

Permission Errors

• Solution: Add permissions to AndroidManifest.xml
• File: android/app/src/main/AndroidManifest.xml

Native Code Errors

• Solution: Check Kotlin/Java code in platform channels
• Files: android/app/src/main/kotlin/

Resource Errors

• Solution: Check drawable/mipmap resources
• Files: android/app/src/main/res/

Best Practices

1. Always check Flutter doctor first: flutter doctor -v
2. Use verbose logging: flutter run --verbose or flutter build apk --verbose
3. Clean before rebuild: flutter clean when in doubt
4. Check device connection: flutter devices and adb devices
5. Read full stack traces: Don't just look at the first error
6. Test on multiple Android versions: Emulators for API 21, 29, 33+
7. Use profile mode for performance: flutter run --profile
8. Enable DevTools: Best for deep debugging

Quick Troubleshooting Checklist

• Run flutter doctor -v - all green?
• Run flutter clean && flutter pub get
• Check adb devices - device connected?
• Check Java version - is it 17?
• Review error logs - full stack trace?
• Try on different device/emulator
• Check android/app/build.gradle.kts config
• Verify AndroidManifest.xml settings
• Test with flutter run --verbose
• Use DevTools for deep analysis

Additional Resources

• Flutter Debugging Docs
• Android Developer Debug Guide
• Flutter DevTools
• ADB Reference