CODEWITHSUNDEEP
androidkotlinandroid-volley
mk4
mk4

Reputation: 93

How can I read a huge file JSON with kotlin?

I'm trying to read a json file regarding my scheduling lessons at university, getting it from this link : http://diag.uniroma1.it/pannello/?q=export_json

I tried to do it using https://developer.android.com/training/volley/simple which works for very simple json file as in https://helloacm.com/api/factor/?cached&n=10 ( where given a number it returns the factorization of itself).

But applying same reasoning doesn't works. Actually the application that first that previously worked well, now crashes.

 fun factors (x: String){

        val queue = Volley.newRequestQueue(this)
        //val url = "https://helloacm.com/api/factor/?cached&n="+x

        val url = "http://diag.uniroma1.it/pannello/?q=export_json"

        var reply : String = ""

        // Request a string response from the provided URL.
        val stringRequest = StringRequest(
            Request.Method.GET, url,
            Response.Listener<String> { response ->
                // Display the first 500 characters of the response string.
                reply = JSONObject(response.toString()).toString()
                output.text=reply
            },
            Response.ErrorListener { error: VolleyError? ->  output.text = error.toString() })

        // Add the request to the RequestQueue.
        queue.add(stringRequest)

    }

What is the problem? Is the file too big respect the previous one? I'm really new in this stuff

Upvotes: 1

Views: 2281

Answers (1)

Maksym S.
Maksym S.

Reputation: 151

The reason why it does not work is that you are receiving a JSON array but you are trying to parse it as a JSON object.

In order to simplify deserialization, you can check Google's Gson Library. Here's an example of Gson implementation:

  1. Add the following dependency to your build.gradle file and sync your project with Gradle:

    implementation 'com.google.code.gson:gson:2.8.6'

  2. Create a model that represents your JSON objects:

    import com.google.gson.annotations.SerializedName

data class DataObject(
    @SerializedName("data")
    val data: String,
    @SerializedName("Descrizione")
    val descrizione: String,
    @SerializedName("Id")
    val id: String,
    @SerializedName("id_aula")
    val idAula: String,
    @SerializedName("minuti_fine")
    val minutiFine: String,
    @SerializedName("minuti_inizio")
    val minutiInizio: String,
    @SerializedName("nome_aula")
    val nomeAula: String,
    @SerializedName("ora_fine")
    val oraFine: String,
    @SerializedName("ora_inizio")
    val oraInizio: String
)

  3. Now you can modify your function to deserialize JSON:

    fun factors(x: String) {

    val queue = Volley.newRequestQueue(this)
    //val url = "https://helloacm.com/api/factor/?cached&n="+x

    val url = "http://diag.uniroma1.it/pannello/?q=export_json"

    var reply: List<DataObject> = listOf()

    // Request a string response from the provided URL.
    val stringRequest = StringRequest(
            Request.Method.GET, url,
            Response.Listener<String> { response ->
                // Display the first 500 characters of the response string.
                reply = Gson().fromJson(response, object : TypeToken<List<DataObject>>() {}.type)
                output.text = reply
            },
            Response.ErrorListener { error: VolleyError? -> output.text = error.toString() })

    // Add the request to the RequestQueue.
    queue.add(stringRequest)
}

Upvotes: 2

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