In-App Purchases应用内购买

When to Use

User needs to implement in-app purchases, subscriptions, paywalls, or monetization flows. Agent handles native APIs (StoreKit 2, Google Play Billing), cross-platform SDKs (RevenueCat, Adapty, Qonversion), paywall design, server verification, and subscription analytics.

Quick Reference

Topic	File
iOS StoreKit 2	INLINECODE0
Android Billing

google-play.md | | Flutter packages | flutter.md | | RevenueCat SDK | revenuecat.md | | Platform comparison | platforms.md | | Server verification | server.md | | Paywall design | paywalls.md | | Subscription metrics | analytics.md | | Testing & sandbox | testing.md |

Core Rules

1. Choose Your Architecture

Approach	When to Use	Tradeoff
Native only	Single platform, full control	More code, no cross-platform sync
RevenueCat/Adapty

Cross-platform, fast launch | 1-2% fee, dependency |

| Hybrid | Native + own backend | Full control, more work |

2. Platform SDKs (Managed)

Platform	Pricing	Best For
RevenueCat	Free <$2.5k MTR, then 1%	Most apps, best docs
Adapty

Free <$10k MTR, then 0.6% | Cost-conscious, A/B paywalls |

| Qonversion | Free <$10k MTR, then 3% | Simple setup | | Superwall | Paywall-focused | Paywall A/B only | | Glassfy | Free <$10k, then 0.5% | Budget option |

3. Product Types

Type	iOS	Android	Use Case
Consumable	✅	✅	Credits, coins, lives
Non-consumable

✅ | ✅ | Unlock feature forever |

| Auto-renewable | ✅ | ✅ | Subscriptions | | Non-renewing | ✅ | ❌ | Season pass, time-limited |

4. Server Verification is Non-Negotiable

Never trust client-side validation alone:

• - iOS: App Store Server API with JWS verification
• Android: Google Play Developer API
• RevenueCat: Webhooks + REST API

5. Handle All Transaction States

State	Action
Purchased	Verify → grant → finish
Pending

Wait, show pending UI |

| Failed | Show error, don't grant | | Deferred | Wait for parental approval | | Refunded | Revoke immediately | | Grace period | Limited access, prompt payment | | Billing retry | Maintain access during retry |

6. Subscription Lifecycle Events

Must handle all of these (native or via webhooks):

• - INITIALPURCHASE → grant access
• RENEWAL → extend access
• CANCELLATION → mark will-expire
• EXPIRATION → revoke access
• BILLINGISSUE → prompt to update payment
• GRACEPERIOD → limited access window
• PRICEINCREASE → consent required (iOS)
• REFUND → revoke + flag user
• UPGRADE/DOWNGRADE → prorate

7. Restore Purchases Always

Required by App Store guidelines:

• - Prominent restore button
• Works for logged-out users
• Handles family sharing (iOS)
• Cross-device sync

8. Paywall Best Practices

See paywalls.md for detailed patterns:

• - Show value before price
• Anchor pricing (3 options, highlight middle)
• Free trial prominent
• Social proof if available
• A/B test everything

9. Testing Strategy

Environment	iOS	Android
Dev/Debug	StoreKit Config file	License testers
Sandbox

Sandbox accounts | Internal testing |

| Production | Real accounts | Production |

Sandbox subscription times:

• - 1 week → 3 minutes
• 1 month → 5 minutes
• 1 year → 1 hour

10. App Store Guidelines

• - No external payment links (anti-steering)
• Must use IAP for digital goods
• Physical goods/services can use Stripe
• Reader apps have exceptions
• 15-30% commission applies

Common Traps

• - Testing with real money → use sandbox/test accounts
• Not finishing transactions → auto-refund (Android 3 days)
• Hardcoding prices → always fetch from store (regional pricing)
• Missing transaction observer → lose purchases made outside app
• No server verification → trivially bypassable
• Ignoring grace period → users churn when they could recover
• Poor paywall UX → kills conversion regardless of price
• Not tracking metrics → can't optimize what you don't measure
• Forgetting restore button → App Store rejection
• Not handling family sharing → confused users