OkHttp en Kotlin

Descarga de un fichero usando OkHttp en Kotlin

AndroidManifest.xml

Añadir el permiso de Internet

Añadir cleartext para poder usar http

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">

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

    <application
        android:usesCleartextTraffic="true"

build.gradle

Añadir viewBinding

plugins {
    id 'com.android.application'
    id 'org.jetbrains.kotlin.android'
}

android {
    namespace 'com.example.okhttpkotlin'
    compileSdk 33

    buildFeatures {
        viewBinding true
    }

Añadir la biblioteca de okhttp a build.gradle (y sincronizar)

Release

dependencies {
    
    implementation("com.squareup.okhttp3:okhttp:4.10.0")
}

strings.xml

<resources>
    <string name="app_name">OkHttp en Kotlin</string>
    <string name="web">https://dam.org.es/ficheros/frases.html</string>
    <string name="descargar">Descargar</string>
</resources>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/myLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_margin="16dp"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/editText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginBottom="10dp"
        android:ems="10"
        android:inputType="textPersonName"
        android:text="@string/web"
        android:textAppearance="@android:style/TextAppearance.Material.Large"
        app:layout_constraintBottom_toTopOf="@+id/button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="344dp"
        android:layout_height="41dp"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginBottom="16dp"
        android:text="@string/descargar"
        app:layout_constraintBottom_toTopOf="@+id/webView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.333"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editText" />

    <WebView
        android:id="@+id/webView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginBottom="16dp"
        app:layout_constraintBottom_toTopOf="@+id/textView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:layout_marginBottom="79dp"
        android:text="Tiempo de descarga"
        android:textAppearance="@android:style/TextAppearance.Material.Large"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/webView" />
</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.xml

class MainActivity : AppCompatActivity(), View.OnClickListener {
    private lateinit var binding: ActivityMainBinding
    var inicio: Long = 0
    lateinit var url: URL

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        val view = binding.root
        setContentView(view)

        binding.button.setOnClickListener(this)
    }

    override fun onClick(p0: View?) {
        try {
            url = URL(binding.editText.text.toString())
            // descarga usando OkHttp
            descargaOkHTTP(url)
        } catch (e: MalformedURLException) {
            e.printStackTrace()
            mostrarError(e.message)
        } catch (ex: IOException) {
            mostrarError(ex.message)
        }
    }

    private fun mostrarError(message: String?) {
        Toast.makeText(this, "Error: $message", Toast.LENGTH_SHORT).show()
    }

    private fun descargaOkHTTP(web: URL) {
        inicio = System.currentTimeMillis()
        //https://square.github.io/okhttp/recipes/#asynchronous-get-kt-java
        val client = OkHttpClient()
        val request = Request.Builder()
            .url(web)
            .build()

        client.newCall(request).enqueue(object : Callback {
            override fun onFailure(call: Call, e: IOException) {
                Log.e("Error: ", e.message!!)
                mostrarRespuesta("Fallo: " + e.message)
            }

            @Throws(IOException::class)
            override fun onResponse(call: Call, response: Response) {
                try {
                    if (!response.isSuccessful) {
                        //throw new IOException("Unexpected code " + response);
                        mostrarRespuesta("Unexpected code: <br>$response")
                    } else {
                        // Read data on the worker thread
                        //https://kotlinlang.org/docs/null-safety.html#the-operator
                        val responseData = response.body!!.string()
                        //Toast.makeText(getApplicationContext(), datos, Toast.LENGTH_SHORT).show();
                        mostrarRespuesta(responseData)
                    }
                } catch (e: Error) {
                    Log.e("Error", "Error when executing get request: " + e.localizedMessage)
                }
            }
        })
    }

    private fun mostrarRespuesta(message: String) {
        var fin = System.currentTimeMillis()

        // Run view-related code back on the main thread
        runOnUiThread {
            binding.webView.loadDataWithBaseURL(url.toString(), message, "text/html", "UTF-8", null)
            binding.textView.text = "Duración: " + (fin - inicio).toString() + " milisegundos"
        }
    }
}

Código de OkHttpKotlin