Mobile Apps 2023W Lecture 8

Resources

Documentation:

• Volley
• Weatherbit - create an account, sign up for the free plan

Tutorials (From GeeksforGeeks.org):

• Volley Tutorial
• Weather App Tutorial

Notes

Lecture 8
---------

Playing with REST APIs in Android

Resources are on the wiki.

Steps:
 * make an empty Compose project (I'm doing it at API 31 level)
 * Add Internet permissions in AndroidManifest.xml:
    <uses-permission android:name="android.permission.INTERNET" />
   (put inside <manifest> at the top level)
 * Add Volley to the project:
   edit build.gradle (Module: <app name>)
   in the dependencies {} section at the bottom, add:

     implementation("com.android.volley:volley:1.2.1")

   (make sure to context select to sync this after adding this)

Code

package carleton.comp2601.weather2601

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.material.MaterialTheme
import androidx.compose.material.Surface
import androidx.compose.material.Text
import androidx.compose.runtime.*
import androidx.compose.ui.Modifier
import carleton.comp2601.weather2601.ui.theme.Weather2601Theme
import com.android.volley.Request
import com.android.volley.RequestQueue
import com.android.volley.toolbox.StringRequest
import com.android.volley.toolbox.Volley
import org.json.JSONObject

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

        val queue = Volley.newRequestQueue(this)

        setContent {
            Weather2601Theme {
                // A surface container using the 'background' color from the theme
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colors.background
                ) {
                    ShowTemp(queue)
                }
            }
        }
    }
}


@Composable
fun ShowTemp(queue: RequestQueue) {
    var temp by remember {
        mutableStateOf("No Temp Yet")
    }

    getTemp({newTemp -> temp = newTemp}, queue)
    Text(text = temp)
}

fun getTemp(updater: (String)->Unit, queue: RequestQueue) {
    val weatherbitKey = "648ba46141624d01a4c4fc5c7b2be856"

    val url: String = "https://api.weatherbit.io/v2.0/current?" +
            "&city=Nashville&state=TN&country=USA" +
            "&key=" + weatherbitKey

    val stringReq = StringRequest(
        Request.Method.GET, url,
        { response ->
            val obj = JSONObject(response)
            val arr = obj.getJSONArray("data")
            val data = arr.getJSONObject(0)
            val newTemp = data.getString("temp")
            updater("Temp in Nashville: " + newTemp)
        },
        { updater("Couldn't get temp")})

    queue.add(stringReq)
}