How do I successfully make an okHttp request in Kotlin

Question

Issues: 1. The request is not hitting my python flask server. 2. My app crashes whenever this code is run. *Note: I have used Postman to test the localhost address, which is successful

I am trying to create an okHttp request in my kotlin android application. I have implemented the needed dependencies in my build.gradle file:

implementation 'com.squareup.okhttp3:okhttp:3.10.0

edit: I included the Internet permission in the manifest file

<uses-permission android:name="android.permission.INTERNET" />

I have tried using my IP as part of the URL, along with a few different localhost links and have determined that the URL is not the issue.
If I am not mistaken, the app crash error occurs during build (), but I cannot wrap my mind around why.

Ideally, this code would hit the rest API and return data (printed as text) on my login screen. After a couple of days of researching and trying other request methods, I am unable to find a solution.

val mTextviewResult: TextView = findViewById(R.id.text_view_result)
            //http client
            var client = OkHttpClient()

            val url = "http://localhost:5000/test"
            val request = Request.Builder()
                .url(url)
                .build()
            Log.d(request.toString(), ":  I build Request")

            client.newCall(request).enqueue(object : Callback {
                override fun onFailure(call: Call, e: IOException) {
                    Log.d(url, ":  I fail")
                    e.printStackTrace()
                }

                @Throws(IOException::class)
                override fun onResponse(call: Call, response: Response) {
                    if (response.isSuccessful()) {
                        Log.d(url, ": I success")
                        val myResponse = response.body()?.string()
                        this@LoginActivity.runOnUiThread(object : Runnable {
                            override fun run() {
                                mTextviewResult.setText(myResponse)
                            }
                        })
                    }
                }
            })

Did you define the permission `` in the manifest file? sometimes this is the main problem XD — Oscar Emilio Perez Martinez, Mar 22 '20 at 04:21
Are you using 10.0.2.2 from within the emulator? https://stackoverflow.com/questions/1621796/accessing-webserver-running-within-eclipse-from-outside-the-workstation/1630532#1630532 — Jesse Wilson, Mar 22 '20 at 10:12
I tried that as well, ,but it actually crashes before reaching that point — zDJ, Mar 23 '20 at 01:20

score 0 · Answer 1 · answered Jan 09 '21 at 18:18

To access localhost you should use local IPv4 + server PORT for localhost.

How to get this IPv4: https://www.whatismybrowser.com/detect/what-is-my-local-ip-address

KOTLIN async request:

private val client = OkHttpClient()

fun run() {
    val request = Request.Builder()
        .url("http://IPv4_FROM_THE_LINK_ABOVE:5000/test")
        .build()

    client.newCall(request).enqueue(object : Callback {
        override fun onFailure(call: Call, e: IOException) {
            e.printStackTrace()
        }

        override fun onResponse(call: Call, response: Response) {
            response.use {
                if (!response.isSuccessful) throw IOException("Unexpected code $response")

                for ((name, value) in response.headers) {
                    println("$name: $value")
                }

                println(response.body!!.string())
            }
        }
    })
}

Install OkHttp: https://square.github.io/okhttp/

How do I successfully make an okHttp request in Kotlin

1 Answers1