CODEWITHSUNDEEP
androidfunctionkotlincallbackandroid-volley
Pratham Vaidya
Pratham Vaidya

Reputation: 105

How to callback a value from Volley On Response function in Kotlin

I am integrating a Login System for that I want the Response.Listener and Response.ErrorListener function to return a Boolean.

I searched on the google and found that it can be done using a callback interface ( This Question ). But I don't know how to do that in Kotlin

[ALSO UPDATED] This is my Kotlin file containing my function which are used by many activities:

package com.pratham.example
// My required imports
import ...  

fun function1(){
...
}
fun function2(){
...
}

// This Auth function will return True if login success

fun auth(activity:Activity):Boolean{
 val queue = Volley.newRequestQueue(activity)
            val req = JsonObjectRequest(Request.Method.POST, url, jsonObj,
                Response.Listener { response ->
                    val JSONObj = response.getString("Status")
                    if(JSONObj=="200"){
                        // return true 
                    }
                    else{
                        // return false 
                    }
                }, Response.ErrorListener {
                    // return  false 
                }
            )
            queue.add(req)
}

fun function4(){
...
}

This function will return true or false according to the Volley Response. How can i return value from a Response.Listener and Response.ErrorListener in Kotlin

Edit:: I tried to use Interface like this

package com.pratham.sitapuriya

import ...

fun function1(){
...
}
fun function2(){
...
}

interface MyInterface {
    fun onCallback(response: Boolean,context:Context)
}

class Login : MyInterface {
    private val myInterface = this

    override fun onCallback(response: Boolean,context:Context) {
        Toast.makeText(context,"Working",Toast.LENGTH_SHORT).show()
    }

    fun auth(activity: Activity): Boolean {

        val sp1 = activity.getSharedPreferences("Login", AppCompatActivity.MODE_PRIVATE)
        if (sp1.contains("token") && sp1.contains("deviceId")) {
            val token = sp1.getString("token", null)
            val deviceId = sp1.getString("deviceId", null)
            if (!token.isNullOrEmpty() && !deviceId.isNullOrEmpty()) {
                //  val url = "http://10.0.2.2:80/Projects/Sitapuriya/login.php"
                val url = activity.getString(R.string.server) + "/tokenAuth.php"
                val params = HashMap<String, String>()
                params["token"] = token
                params["deviceId"] = deviceId
                val jsonObj = JSONObject(params)
                val queue = Volley.newRequestQueue(activity)
                val req = JsonObjectRequest(Request.Method.POST, url, jsonObj,
                    Response.Listener { response ->
                        val JSONObj = response.getString("Status")
                        if (JSONObj == "200") {
                            // return true
                            myInterface.onCallback(true,activity)
                        } else {
                            // return false
                            myInterface.onCallback(false,activity)
                        }
                    }, Response.ErrorListener {
                        // return  false
                        myInterface.onCallback(false,activity)
                    }
                )
                queue.add(req)


            } else {
                return false
            }

        } else {
            return false
        }

        return false
    }
}

fun function4(){
...
}

But now i have no idea that how the callback will return value in auth() function and also how I'll be calling this auth() fucntion in my other activities .

Please help I have never used a callback before..

Upvotes: 0

Views: 4744

Answers (1)

Belal Khan
Belal Khan

Reputation: 2119

You can't, the code you have executes asynchronously so you can't have the return statement there. But it doesn't mean you can not get the value. The easiest option is create a LiveData<Boolean> and observe it in your activity. When the value changes you will get notified.

The next thing you can do is you can create an interface. 

interface MyCallback{
    fun onValueChanged()
}

Then implement this interface in your activity and override the method. Then you can use it to get a callback when your asynchronous call finishes. See the below code. 

interface MyInterface{
    fun onCallback(response:Boolean)
}

class LoginActivity : AppCompatActivity(), AuthListener, MyInterface {

    val myInterface = this

    override fun onCallback(response: Boolean) {

    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val queue = Volley.newRequestQueue(activity)
        val req = JsonObjectRequest(Request.Method.POST, url, jsonObj,
            Response.Listener { response ->
                val JSONObj = response.getString("Status")
                if(JSONObj=="200"){
                    //return true
                    myInterface.onCallback(true)
                }
                else{
                    myInterface.onCallback(false)
                }
            }, Response.ErrorListener {
                // return  false 
            }
        )
        queue.add(req)

    }
}

Hope this helps. Thank You :)

Upvotes: 2

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