Khmer Angkor Academy | សិក្សាបង្កើតគេហទំព័រជាភាសាខ្មែរ

Networking

Android apps ច្រើនត្រូវការទំនាក់ទំនងជាមួយ internet ដើម្បីទាញយកទិន្នន័យពី servers (APIs)។ Networking គឺជា core skill សម្រាប់ modern apps!

🌐 Network Communication Flow

┌─────────────────┐
│  Android App    │  ──► Send HTTP Request
└────────┬────────┘      (GET, POST, PUT, DELETE)
         │
         ▼ Internet
         │
┌────────▼────────┐
│   Web Server    │  ──► Process request
│   (API/Backend) │      Execute logic
└────────┬────────┘
         │
         ▼ Response
         │
┌────────▼────────┐
│  Android App    │  ──► Parse JSON/XML
│  (Display data) │      Update UI
└─────────────────┘

📡 HTTP Request Methods

Method	Purpose	Example
GET	Retrieve data (read-only)	Get user list, Get post by ID
POST	Create new resource	Create user, Submit form
PUT	Update entire resource	Update user profile
PATCH	Update partial resource	Update user email only
DELETE	Delete resource	Delete user account

📚 Android Networking Libraries

Library	Pros	Cons	When to Use
Volley	✅ Easy to use ✅ Built-in caching ✅ Request queue	❌ Limited features ❌ Verbose code	Simple APIs, Quick tasks
Retrofit	✅ Type-safe ✅ Clean syntax ✅ Powerful	❌ Learning curve ❌ More setup	✅ RESTful APIs (Recommended)
OkHttp	✅ Low-level control ✅ HTTP/2 support ✅ WebSocket	❌ More code ❌ Manual parsing	Custom protocols, WebSockets

🆚 Volley vs Retrofit (Detailed)

Feature	Volley	Retrofit
Syntax	⚠️ Verbose, callback hell	✅ Clean, interface-based
JSON Parsing	❌ Manual	✅ Automatic (Gson/Moshi)
Type Safety	❌ String-based	✅ Type-safe models
Request/Response	⚠️ JSONObject/JSONArray	✅ POJOs (User, Post objects)
Error Handling	⚠️ Manual parsing	✅ Structured callbacks
Caching	✅ Built-in	✅ Via OkHttp interceptor
File Upload	⚠️ Complex	✅ Simple
Recommendation	Legacy apps, Simple tasks	✅ Modern apps (Use this!)

📊 Response Status Codes

Code Range	Meaning	Common Codes
2xx Success	✅ Request succeeded	200 OK, 201 Created, 204 No Content
3xx Redirection	🔄 Further action needed	301 Moved, 304 Not Modified
4xx Client Error	❌ Client mistake	400 Bad Request, 401 Unauthorized, 404 Not Found
5xx Server Error	⚠️ Server problem	500 Internal Error, 503 Service Unavailable

🔐 Network Security

Security Practice	Why Important
🔒 Use HTTPS	Encrypt data in transit (not HTTP!)
🔑 API Keys	Don't hardcode in code (use BuildConfig)
📌 Certificate Pinning	Prevent man-in-the-middle attacks
⏱️ Timeouts	Handle slow/failed connections
🔄 Retry Logic	Handle temporary network failures

⚠️ Permission Required: ត្រូវបន្ថែម <uses-permission android:name="android.permission.INTERNET"/> ក្នុង AndroidManifest.xml!

✅ Best Practice: ប្រើ Retrofit + OkHttp + Gson សម្រាប់ modern Android apps! មិនត្រូវធ្វើ network calls នៅលើ main thread!

Java Code

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