Summary of steps for developing apps

The following are detailed explanations of the logical implementation steps of using IDEA backend Java development (such as Spring Boot) and Android Studio front-end development app:

---

1. Technical selection

1. Communication Protocol: Recommended to use RESTful API (HTTP/HTTPS)
2. Data format: JSON (lightweight and cross-platform)
3. Backend framework：Spring Boot
4. Android network library：Retrofit + OkHttp
5. Interface testing tool：Postman

---

2. Implementation steps

1. Backend development (IDEA Spring Boot)

// Example: User API interface
 @RestController
 @CrossOrigin(origins = "*") // Solve cross-domain problems
 @RequestMapping("/api/users")
 public class UserController {
    
     @Autowired
     private UserService userService;

     // Create a user
     @PostMapping
     public ResponseEntity<User> createUser(@RequestBody User user) {
         User createdUser = (user);
         return new ResponseEntity<>(createdUser, );
     }

     // Get the user list
     @GetMapping
     public List<User> getAllUsers() {
         return ();
     }

     // Query the user by ID
     @GetMapping("/{id}")
     public ResponseEntity<User> getUserById(@PathVariable Long id) {
         return (id)
                 .map(user -> new ResponseEntity<>(user, ))
                 .orElse(new ResponseEntity<>(HttpStatus.NOT_FOUND));
     }
 }

Key configurations：

# 
=8080
=jdbc:mysql://localhost:3306/mydb
-auto=update

2. Front-end development (Android Studio)

Step 1: Add dependencies

//  (Module)
dependencies {
    implementation '.retrofit2:retrofit:2.9.0'
    implementation '.retrofit2:converter-gson:2.9.0'
    implementation '.okhttp3:logging-interceptor:4.9.3'
}

Step 2: Create a Data Model

// 
data class User(
    @SerializedName("id") val id: Long,
    @SerializedName("name") val name: String,
    @SerializedName("email") val email: String
)

Step 3: Configure Retrofit

//
 object ApiClient {
     private const val BASE_URL = "http://10.0.2.2:8080/api/" // Android emulator accesses native address

     private val okHttpClient = ()
         .addInterceptor(HttpLoggingInterceptor().apply {
             level =
         })
         .build()

     private val retrofit = ()
         .baseUrl(BASE_URL)
         .client(okHttpClient)
         .addConverterFactory(())
         .build()

     val userService: UserService = (UserService::)
 }

Step 4: Define API Interface

// 
interface UserService {
    @GET("users")
    suspend fun getUsers(): Response<List<User>>

    @POST("users")
    suspend fun createUser(@Body user: User): Response<User>

    @GET("users/{id}")
    suspend fun getUserById(@Path("id") id: Long): Response<User>
}

Step 5: Initiate a network request

//
 class MainActivity: AppCompatActivity() {
     private val userService =

     override fun onCreate(savedInstanceState: Bundle?) {
         (savedInstanceState)
         setContentView(.activity_main)

         CoroutineScope().launch {
             try {
                 // Get the user list
                 val response = ()
                 if () {
                     val users = ()
                     users?.forEach { user ->
                         ("API_RESPONSE", "User: ${}")
                     }
                 }
             } catch (e: Exception) {
                 ()
             }
         }
     }
 }

---

3. Key points of joint adjustment

1. IP address configuration：

   • The emulator accesses the machine:10.0.2.2
   • Real-time debugging requires ensuring that the mobile phone and PC are on the same LAN, and the LAN IP of the PC is used.

2. Network permissions：

   <!--  -->
   <uses-permission android:name="" />
   

---

4. Test process

1. Testing backend interfaces using Postman
2. Start Android emulator
3. View Logcat output

---