Synchronous API call using retrofit execute

Question

Im trying to do a synchronous api call in Kotlin android, actually I'm having a function with 2 parameters and I need to make a post request and get a particular response for it and depending on the response i have to return true or false.

I have tried enqueue() & execute() from Retrofit2 but execute() works on the UI thread. even tried making a thread and run still the return statement execute before the response.

        private fun check(v1: String, v2: String): Boolean {

            val vObj = ValidateObj( v1, v2 )
            val boolcheck = false
            Thread {
                try {
                    val retrofit = ServiceBuilder.buildService(API::class.java)
                    val res = retrofit.validate(vObj).execute() 
                    boolcheck = res.code() == 200
                } catch (e: Exception) {
                    boolcheck = false
                }
            }.start()
            return true
        }

I have seen most the the answers for the same nothing seems working for me as the code provided was not complete/ wrong.

Please help with a sample code if possible. (Thanks in advance.)

Answer 1

The problem with your sample code is that inside your function check(p1, p2) you start a new Thread. This means your Thread which started the function will continue and return true. You must add a way to wait for the execution of the call and then continue your process with the result.

There are multiple ways to achieve this:

1. with Callback

private fun check(v1: String, v2: String, onResult: (Boolean) -> Unit) {
            val vObj = ValidateObj( v1, v2 )
            Thread {
                val result = runCatching {
                    val retrofit = ServiceBuilder.buildService(API::class.java)
                    val res = retrofit.validate(vObj).execute() 
                    res.code() == 200
                }.getOrDefault(false)

                onResult(result) // result will then be on the other thread and you have to switch back if necessary
            }.start()
        }


//with Coroutine
private fun check(v1: String, v2: String, onResult: (Boolean) -> Unit) {
            val vObj = ValidateObj( v1, v2 )
            CoroutineScope(Dispatchers.IO).launch {
                val result = runCatching {
                    val retrofit = ServiceBuilder.buildService(API::class.java)
                    val res = retrofit.validate(vObj).execute() 
                    res.code() == 200
                }.getOrDefault(false)

                onResult(result) // result will then be on the other thread and you have to switch back if necessary

                // e.g. CoroutineScope(Dispatchers.Main).launch{onResult(result)}
              
            }
        }


fun logic(){
    check(p1, p2){ boolean ->
       // continue your logic
    }
}

2. with Coroutines

private suspend fun check(v1: String, v2: String): Boolean = 
        withContext(Dispatchers.IO){
            val vObj = ValidateObj( v1, v2 )
            
            runCatching {
                    val retrofit = ServiceBuilder.buildService(API::class.java)
                    val res = retrofit.validate(vObj).execute() 
                    res.code() == 200
                }.getOrDefault(false)
       }    

fun logic{
    
    //use function inside a coroutine, e.g.
    CoroutineScope(Dispatchers.Main).launch{
        val checkResult = check(p1, p2)

        ...
    }

}