activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              xmlns:tools="http://schemas.android.com/tools"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:orientation="vertical"
              tools:context=".MainActivity">

    <EditText
            android:id="@+id/inputToTranslate"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_marginTop="48dp"
            android:layout_marginBottom="16dp"
            android:ems="10"
            android:hint="Enter text"
            android:inputType="text" />

    <Button
            android:id="@+id/translateButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_marginBottom="32dp"
            android:text="Translate" />

    <TextView
            android:id="@+id/translatedText"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:textSize="16sp" />
</LinearLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android">
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
    <!--Activities below as usual-->

</manifest>

MainActivity.kt

class MainActivity : AppCompatActivity() {

    private var translate: Translate? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        getTranslateService()
        translateButton.setOnClickListener {
            if (checkInternetConnection()) {
                translate()
            } else {
                translatedText.text = getString(R.string.no_connection)
            }
        }
    }

    private fun getTranslateService() {
        try {
            resources.openRawResource(R.raw.credentials).use { `is` ->
                val myCredentials = GoogleCredentials.fromStream(`is`)
                val translateOptions = TranslateOptions.newBuilder().setCredentials(myCredentials).build()
                translate = translateOptions.service
            }
        } catch (ioe: IOException) {
            ioe.printStackTrace()

        }

    }

    private fun translate() {
        val translation = translate!!.translate(
            inputToTranslate.text.toString(),
            Translate.TranslateOption.targetLanguage("tr"),
            Translate.TranslateOption.model("base")
        )

        //Translated text is set to the TextView:
        translatedText.text = translation.translatedText

    }

    private fun checkInternetConnection(): Boolean {
        val cm = this.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
        val activeNetwork: NetworkInfo? = cm.activeNetworkInfo
        return activeNetwork?.isConnected == true
    }

}