500 Error code with "Internal server Error" message, while doing POST method using API in android application

Question

For API confirmation, I have tried in POSTMAN app, But response is getting properly and the data has been inserted successfully. Below is the result of POSTMAN.

Also getting following errors in Logcat.

2021-06-01 17:56:58.522 16534-16534/? E/ample.addcours: Unknown bits set in runtime_flags: 0x8000
2021-06-01 17:56:58.893 1791-2057/? E/SurfaceFlinger: ro.sf.lcd_density must be defined as a build property
2021-06-01 17:56:58.897 1791-1897/? E/SurfaceFlinger: ro.sf.lcd_density must be defined as a build property
2021-06-01 17:57:01.325 1887-1887/? E/netmgr: Failed to open QEMU pipe 'qemud:network': Invalid argument
2021-06-01 17:57:01.713 1895-1895/? E/wifi_forwarder: RemoteConnection failed to initialize: RemoteConnection failed to open pipe

2021-06-01 17:57:48.882 1746-16596/? E/ResolverController: No valid NAT64 prefix (100, <unspecified>/0)
2021-06-01 17:57:48.915 2062-2154/system_process E/InputDispatcher: Window handle Window{33fd41d u0 com.example.addcourse/com.example.addcourse.RegisterActivity} has no registered input channel
2021-06-01 17:57:48.934 2062-6837/system_process E/InputDispatcher: Window handle Window{33fd41d u0 com.example.addcourse/com.example.addcourse.RegisterActivity} has no registered input channel 

As am new to android application. this is my first program using API concepts. Here is the code which I tried. Please guide me find the issue.

data class RegisterResponse(
    @SerializedName("status")
    val status: Int,
    @SerializedName("message")
    val message: String
)
 object ApiClient {

    // retrofit is HTTP client which can send request to API
    fun getRetrofit() : Retrofit {

        val retrofit = Retrofit.Builder()
            .addConverterFactory(GsonConverterFactory.create())  // this is used to automatically convert json string into java/kotlin object and java/kotlin object into json string whenever required
            .baseUrl("https://XXXX.com/XXXX/api/index.php/")

            .build()

        return retrofit
    }
}

interface ApiService { 
 //   @Headers("Content-type: application/json")
    @POST("Course/addCourse")
    @FormUrlEncoded

    fun signup(
        @Field("course_title") title: String,
        @Field("course_desc") desc: String,
        @Field("course_fees") fees: String
    ) : Call<RegisterResponse>

}

class RegisterActivity : AppCompatActivity() {
    lateinit var binding: ActivityRegisterBinding
    lateinit var retrofit: Retrofit
    lateinit var apiSerice: ApiService

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityRegisterBinding.inflate(layoutInflater)
        setContentView(binding.root)
        retrofit = ApiClient.getRetrofit()
        apiSerice = retrofit.create(ApiService::class.java)
        binding.btnRegister.setOnClickListener {
            register()
        }
    }

    private fun register() {
        val title = binding.etCourseTitle.text.toString()
        val desc = binding.etCourseDescription.text.toString()
        val fees = binding.etCourseFee.text.toString()

        val call = apiSerice.signup(title, desc, fees)

        val progressDialog = ProgressDialog(this);
        progressDialog.setMessage("Please wait. We are processing your request")
        progressDialog.setCancelable(false)

        call.enqueue(object: Callback<RegisterResponse> {
            override fun onResponse(call: Call<RegisterResponse>, response: Response<RegisterResponse>) {

                progressDialog.dismiss()

                if(response.isSuccessful) {
                    val registerResponse: RegisterResponse? = response.body()
                    if(registerResponse?.status == 0) {
                        Toast.makeText(baseContext, "Registered successfully", Toast.LENGTH_LONG).show()
                    } else {
                        Toast.makeText(baseContext, registerResponse?.message, Toast.LENGTH_LONG).show()
                    }
                } else {
                    Toast.makeText(baseContext, response.message()+"/nSomething went wrong. Please retry.(1)", Toast.LENGTH_LONG).show()
                }
            }
            override fun onFailure(call: Call<RegisterResponse>, t: Throwable) {
                progressDialog.dismiss()
                Toast.makeText(baseContext, t.message+"Something went wrong. Please retry.(2)", Toast.LENGTH_LONG).show()
            }
        })
        progressDialog.show()
    }
}

Answer 1

Your API requires JSON data in the request body. But you're trying to send the data in the form FormURLEncoded.

Create a data model class in Kotlin like below.

data class Course(

    @SerializedName("course_title")
    val courseTitle: String,

    @SerializedName("course_desc")
    val courseDesc: String,

    @SerializedName("course_fees")
    val courseFees: String
)

And do the changes in ApiService.kt file

interface ApiService { 

    @POST("Course/addCourse")
    fun signup(
       @Body data: Course
    ): Call<RegisterResponse>

}

In Activity or Fragment prepare the object of the Course class type and pass it to the signup() function.

// rest of your code
// .....
val data = Course("Some course title", "Course desc", "150")

val service = .....

// call and pass parameter

val call = serivce.signup(data)

// handle response here