android-platform

Android Platform

Overview

Guide users through Android platform features, runtime permissions, and troubleshooting. Cover modern APIs that replace older approaches, permission best practices, and common error resolution. Emphasis on current best practices — many online tutorials teach deprecated patterns.

Disclaimer: This skill provides educational guidance for learning Android development. For production apps handling sensitive user data, payment processing, authentication, or security-critical features, consult a professional Android developer or security auditor.

Runtime Permissions Decision Tree

Before requesting a permission, check if you actually need it:

Do I need this capability?
├── Camera → REQUEST_PERMISSION (CAMERA)
├── Location → REQUEST_PERMISSION (ACCESS_FINE_LOCATION or COARSE)
├── Pick a photo/video → USE Photo Picker (no permission needed!)
├── Read/write media → USE MediaStore API (scoped storage, no permission needed for own files)
├── Read all files → AVOID if possible; REQUEST_PERMISSION (READ_MEDIA_IMAGES etc.) if needed
├── Notifications (API 33+) → REQUEST_PERMISSION (POST_NOTIFICATIONS)
├── Bluetooth (API 31+) → REQUEST_PERMISSION (BLUETOOTH_CONNECT)
└── Contacts, Calendar, etc. → REQUEST_PERMISSION (specific permission)

Permission Request Flow

1. Check if the feature is essential — if optional, offer degraded experience without it
2. Explain why before requesting — users grant permissions at higher rates when they understand the reason
3. Use ActivityResultContracts.RequestPermission() (not the deprecated onRequestPermissionsResult)
4. Handle denial gracefully — show explanation, offer alternative, never block the app
5. Handle "Don't ask again" — direct user to Settings with a clear explanation

Modern Platform Features

Features that replace older approaches — present with rolling API requirements:

Feature	Min API	What It Replaces	Why It Matters
Photo Picker	19 (backported)	READ_EXTERNAL_STORAGE for media selection	No permission needed; scoped, privacy-preserving
Credential Manager	23 (backported)	SmartLock, legacy login flows	Passkeys, passwords, federated sign-in in one API
Predictive Back	34+ (opt-in, default on API 35+)	onBackPressed() override	System back gesture shows preview; breaks apps that don't handle it
Per-app Language	33+	Manual locale switching	System-managed language per app
Baseline Profiles	24+	No equivalent	15-50% cold start improvement; profiles compiled AOT
Scoped Storage	29+ (enforced 30+)	WRITE_EXTERNAL_STORAGE	App-specific dirs without permission; MediaStore for shared media
Foreground Service Types	34+	Untyped foreground services	Must declare type (camera, location, etc.) in manifest
Adaptive Layouts	Recommended for all	Fixed orientation lock	Can't restrict orientation on large screens (Android 16+)

Predictive Back — Important Note

Predictive Back is on by default starting API 35. Apps that override onBackPressed() or use FLAG_ACTIVITY_CLEAR_TOP carelessly will break. To prepare:

• Use OnBackPressedCallback instead of overriding onBackPressed()
• Enable android:enableOnBackInvokedCallback="true" in the manifest to test
• Compose Navigation handles this correctly by default

Troubleshooting Quick Reference

Error / Symptom	Likely Cause	Fix
Gradle sync failed	Version mismatch, missing SDK	Check references/troubleshooting.md
Unresolved reference after adding dependency	Missing Gradle sync	Sync Gradle files
App crashes on rotation	State not in ViewModel	Move state to ViewModel + StateFlow
NetworkOnMainThreadException	Network call on Main thread	Use Dispatchers.IO in repository
Compose preview blank	Missing @Preview parameter defaults	Add default parameter values
INSTALL_FAILED_OLDER_SDK	Device API < minSdk	Lower minSdk or use newer device
Emulator won't start	Hardware acceleration disabled	Enable VT-x/AMD-V in BIOS
Could not find :compose-bom	Missing Google Maven repository	Add google() to repositories block
R8/ProGuard strips needed class	Missing keep rule	Add -keep rule for the class
java.lang.OutOfMemoryError during build	Insufficient Gradle heap	Increase org.gradle.jvmargs in gradle.properties

Security Awareness

Flag these areas for professional review — they're beyond educational scope:

• Authentication & user data — Use Credential Manager for basic login; complex auth (OAuth, HIPAA data) needs professional review
• Payment processing — Use Google Play Billing Library; never handle raw payment data
• Encryption — Use Jetpack Security (EncryptedSharedPreferences, EncryptedFile) for local secrets
• Network security — Enable certificate pinning for sensitive APIs; use Network Security Config
• API keys — Never commit to source control; use local.properties or BuildConfig injection

References

• references/permissions-guide.md — Runtime permissions patterns with complete code examples
• references/platform-features.md — Credential Manager, Predictive Back, Photo Picker, Baseline Profiles deep dives
• references/troubleshooting.md — Common errors, Gradle failures, crash debugging, emulator fixes