CODEWITHSUNDEEP
androidkotlinandroid-livedatamutablelivedata
Arpan Sircar
Arpan Sircar

Reputation: 530

LiveData Doesn't Return The Updated String

I'm trying to learn LiveData. I wrote a sample code to download some API data asynchronously and return it to the MainActivity for being logged. I'm not using ViewModel as I've yet to learn it.

Here's the code for the DownloadInfoClass.kt in which I'm placing the LiveData object:

package com.example.kotlincurrency

import androidx.lifecycle.MutableLiveData
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers.IO
import kotlinx.coroutines.Dispatchers.Main
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext
import java.io.InputStreamReader
import java.lang.Exception
import java.net.HttpURLConnection
import java.net.URL

class DownloadParseInfoClass {

    private var mutableLiveData: MutableLiveData<String> = MutableLiveData()
    private var result: String = ""

    fun downloadMethod(urls: String) = CoroutineScope(Main).launch {
        result = infoDownloadMethod(urls)
    }

    private suspend fun infoDownloadMethod(urls: String): String{
        var result = ""

        withContext(IO){
            try {
                val url = URL(urls)
                val httpURLConnection = url.openConnection() as HttpURLConnection
                val inputStream = httpURLConnection.inputStream
                val inputStreamReader = InputStreamReader(inputStream)

                var data: Int = inputStreamReader.read()
                while (data != -1){
                    val current = data.toChar().toString()
                    result += current
                    data = inputStreamReader.read()
                }
            }

            catch (e: Exception){
                e.printStackTrace()
            }
        }

        return result
    }

    fun getMutableLiveData(): MutableLiveData<String>{
        mutableLiveData.value = result
        return mutableLiveData
    }

}

In the MainActivity.kt class, I'm placing the Observer in the OnCreate method. Here's the code:

override fun onCreate(savedInstanceState: Bundle?){
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        setActionBarMethod()
        initViews()

        val downloadParseInfoClass = DownloadParseInfoClass()
        downloadParseInfoClass.downloadMethod("https://api.exchangeratesapi.io/latest?base=INR")
        downloadParseInfoClass.getMutableLiveData().observe(this, Observer {
            Log.i("Result", it)
        })
    }

I don't understand why it's not logging the data. Could it because I'm not using a ViewModel? I mean, all the blogs that I've gone through for a solution, each of them has used a ViewModel with LiveData.

Upvotes: 0

Views: 151

Answers (1)

Blackbelt
Blackbelt

Reputation: 157447

you need to post the new value after reading it from the inputstream.

while (data != -1){
     val current = data.toChar().toString()
     result += current
     data = inputStreamReader.read()
} 
mutableLiveData.postValue(result)

Upvotes: 2

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