diff --git a/app/src/main/java/ai/elimu/content_provider/ui/audio/AudiosFragment.java b/app/src/main/java/ai/elimu/content_provider/ui/audio/AudiosFragment.java
deleted file mode 100644
index 2b3fc29e..00000000
--- a/app/src/main/java/ai/elimu/content_provider/ui/audio/AudiosFragment.java
+++ /dev/null
@@ -1,177 +0,0 @@
-package ai.elimu.content_provider.ui.audio;
-
-import android.os.Bundle;
-import android.util.Log;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.view.ViewGroup;
-import android.widget.ProgressBar;
-import android.widget.TextView;
-
-import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
-import androidx.fragment.app.Fragment;
-import androidx.lifecycle.Observer;
-import androidx.lifecycle.ViewModelProvider;
-
-import com.google.android.material.snackbar.Snackbar;
-
-import java.io.File;
-import java.io.FileNotFoundException;
-import java.io.FileOutputStream;
-import java.io.IOException;
-import java.util.List;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-
-import ai.elimu.content_provider.BaseApplication;
-import ai.elimu.content_provider.R;
-import ai.elimu.content_provider.rest.AudiosService;
-import ai.elimu.content_provider.room.GsonToRoomConverter;
-import ai.elimu.content_provider.room.dao.AudioDao;
-import ai.elimu.content_provider.room.db.RoomDb;
-import ai.elimu.content_provider.room.entity.Audio;
-import ai.elimu.content_provider.util.FileHelper;
-import ai.elimu.content_provider.util.MultimediaDownloader;
-import ai.elimu.model.v2.gson.content.AudioGson;
-import retrofit2.Call;
-import retrofit2.Callback;
-import retrofit2.Response;
-import retrofit2.Retrofit;
-
-public class AudiosFragment extends Fragment {
-
-    private AudiosViewModel audiosViewModel;
-
-    private ProgressBar progressBar;
-
-    private TextView textView;
-
-    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
-        Log.i(getClass().getName(), "onCreateView");
-
-        audiosViewModel = new ViewModelProvider(this).get(AudiosViewModel.class);
-        View root = inflater.inflate(R.layout.fragment_audios, container, false);
-        progressBar = root.findViewById(R.id.progress_bar_audios);
-        textView = root.findViewById(R.id.text_audios);
-        audiosViewModel.getText().observe(getViewLifecycleOwner(), new Observer<String>() {
-            @Override
-            public void onChanged(@Nullable String s) {
-                Log.i(getClass().getName(), "onChanged");
-                textView.setText(s);
-            }
-        });
-        return root;
-    }
-
-    @Override
-    public void onStart() {
-        Log.i(getClass().getName(), "onStart");
-        super.onStart();
-
-        // Download Audios from REST API, and store them in the database
-        BaseApplication baseApplication = (BaseApplication) getActivity().getApplication();
-        Retrofit retrofit = baseApplication.getRetrofit();
-        AudiosService audiosService = retrofit.create(AudiosService.class);
-        Call<List<AudioGson>> audioGsonsCall = audiosService.listAudios();
-        Log.i(getClass().getName(), "audioGsonsCall.request(): " + audioGsonsCall.request());
-        audioGsonsCall.enqueue(new Callback<List<AudioGson>>() {
-
-            @Override
-            public void onResponse(Call<List<AudioGson>> call, Response<List<AudioGson>> response) {
-                Log.i(getClass().getName(), "onResponse");
-
-                Log.i(getClass().getName(), "response: " + response);
-                if (response.isSuccessful()) {
-                    List<AudioGson> audioGsons = response.body();
-                    Log.i(getClass().getName(), "audioGsons.size(): " + audioGsons.size());
-
-                    if (audioGsons.size() > 0) {
-                        processResponseBody(audioGsons);
-                    }
-                } else {
-                    // Handle error
-                    Snackbar.make(textView, response.toString(), Snackbar.LENGTH_LONG)
-                            .setBackgroundTint(getResources().getColor(R.color.deep_orange_darken_4))
-                            .show();
-                    progressBar.setVisibility(View.GONE);
-                }
-            }
-
-            @Override
-            public void onFailure(Call<List<AudioGson>> call, Throwable t) {
-                Log.e(getClass().getName(), "onFailure", t);
-
-                Log.e(getClass().getName(), "t.getCause():", t.getCause());
-
-                // Handle error
-                Snackbar.make(textView, t.getCause().toString(), Snackbar.LENGTH_LONG)
-                        .setBackgroundTint(getResources().getColor(R.color.deep_orange_darken_4))
-                        .show();
-                progressBar.setVisibility(View.GONE);
-            }
-        });
-    }
-
-    private void processResponseBody(List<AudioGson> audioGsons) {
-        Log.i(getClass().getName(), "processResponseBody");
-
-        ExecutorService executorService = Executors.newSingleThreadExecutor();
-        executorService.execute(new Runnable() {
-            @Override
-            public void run() {
-                Log.i(getClass().getName(), "run");
-
-                RoomDb roomDb = RoomDb.getDatabase(getContext());
-                AudioDao audioDao = roomDb.audioDao();
-
-                // Empty the database table before downloading up-to-date content
-                audioDao.deleteAll();
-                // TODO: also delete corresponding audio files (only those that are no longer used)
-
-                for (AudioGson audioGson : audioGsons) {
-                    Log.i(getClass().getName(), "audioGson.getId(): " + audioGson.getId());
-
-                    Audio audio = GsonToRoomConverter.getAudio(audioGson);
-
-                    // Check if the corresponding audio file has already been downloaded
-                    File audioFile = FileHelper.getAudioFile(audioGson, getContext());
-                    Log.i(getClass().getName(), "audioFile: " + audioFile);
-                    Log.i(getClass().getName(), "audioFile.exists(): " + audioFile.exists());
-                    if (!audioFile.exists()) {
-                        // Download file bytes
-                        BaseApplication baseApplication = (BaseApplication) getActivity().getApplication();
-                        String downloadUrl = baseApplication.getBaseUrl() + audioGson.getBytesUrl();
-                        Log.i(getClass().getName(), "downloadUrl: " + downloadUrl);
-                        byte[] bytes = MultimediaDownloader.downloadFileBytes(downloadUrl);
-                        Log.i(getClass().getName(), "bytes.length: " + bytes.length);
-
-                        // Store the downloaded file in the external storage directory
-                        try {
-                            FileOutputStream fileOutputStream = new FileOutputStream(audioFile);
-                            fileOutputStream.write(bytes);
-                        } catch (FileNotFoundException e) {
-                            Log.e(getClass().getName(), null, e);
-                        } catch (IOException e) {
-                            Log.e(getClass().getName(), null, e);
-                        }
-                        Log.i(getClass().getName(), "audioFile.exists(): " + audioFile.exists());
-                    }
-
-                    // Store the Audio in the database
-                    audioDao.insert(audio);
-                    Log.i(getClass().getName(), "Stored Audio in database with ID " + audio.getId());
-                }
-
-                // Update the UI
-                List<Audio> audios = audioDao.loadAll();
-                Log.i(getClass().getName(), "audios.size(): " + audios.size());
-                getActivity().runOnUiThread(() -> {
-                    textView.setText("audios.size(): " + audios.size());
-                    Snackbar.make(textView, "audios.size(): " + audios.size(), Snackbar.LENGTH_LONG).show();
-                    progressBar.setVisibility(View.GONE);
-                });
-            }
-        });
-    }
-}
diff --git a/app/src/main/java/ai/elimu/content_provider/ui/audio/AudiosFragment.kt b/app/src/main/java/ai/elimu/content_provider/ui/audio/AudiosFragment.kt
new file mode 100644
index 00000000..c9cad71c
--- /dev/null
+++ b/app/src/main/java/ai/elimu/content_provider/ui/audio/AudiosFragment.kt
@@ -0,0 +1,166 @@
+package ai.elimu.content_provider.ui.audio
+
+import ai.elimu.content_provider.BaseApplication
+import ai.elimu.content_provider.R
+import ai.elimu.content_provider.rest.AudiosService
+import ai.elimu.content_provider.room.GsonToRoomConverter
+import ai.elimu.content_provider.room.db.RoomDb
+import ai.elimu.content_provider.util.FileHelper
+import ai.elimu.content_provider.util.MultimediaDownloader
+import ai.elimu.model.v2.gson.content.AudioGson
+import android.os.Bundle
+import android.util.Log
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.ProgressBar
+import android.widget.TextView
+import androidx.fragment.app.Fragment
+import androidx.lifecycle.Observer
+import androidx.lifecycle.ViewModelProvider
+import com.google.android.material.snackbar.Snackbar
+import retrofit2.Call
+import retrofit2.Callback
+import retrofit2.Response
+import java.io.FileNotFoundException
+import java.io.FileOutputStream
+import java.io.IOException
+import java.util.concurrent.Executors
+
+class AudiosFragment : Fragment() {
+    private var audiosViewModel: AudiosViewModel? = null
+
+    private var progressBar: ProgressBar? = null
+
+    private var textView: TextView? = null
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        Log.i(javaClass.name, "onCreateView")
+
+        audiosViewModel = ViewModelProvider(this).get(AudiosViewModel::class.java)
+        val root = inflater.inflate(R.layout.fragment_audios, container, false)
+        progressBar = root.findViewById(R.id.progress_bar_audios)
+        textView = root.findViewById(R.id.text_audios) as? TextView
+        audiosViewModel!!.text.observe(viewLifecycleOwner, object : Observer<String?> {
+            override fun onChanged(s: String?) {
+                Log.i(javaClass.name, "onChanged")
+                textView?.text = s
+            }
+        })
+        return root
+    }
+
+    override fun onStart() {
+        Log.i(javaClass.name, "onStart")
+        super.onStart()
+
+        // Download Audios from REST API, and store them in the database
+        val baseApplication = activity!!.application as BaseApplication
+        val retrofit = baseApplication.retrofit
+        val audiosService = retrofit.create(AudiosService::class.java)
+        val audioGsonsCall = audiosService.listAudios()
+        Log.i(javaClass.name, "audioGsonsCall.request(): " + audioGsonsCall.request())
+        audioGsonsCall.enqueue(object : Callback<List<AudioGson>> {
+            override fun onResponse(
+                call: Call<List<AudioGson>>,
+                response: Response<List<AudioGson>>
+            ) {
+                Log.i(javaClass.name, "onResponse")
+
+                Log.i(javaClass.name, "response: $response")
+                if (response.isSuccessful) {
+                    val audioGsons = response.body()!!
+                    Log.i(javaClass.name, "audioGsons.size(): " + audioGsons.size)
+
+                    if (audioGsons.size > 0) {
+                        processResponseBody(audioGsons)
+                    }
+                } else {
+                    // Handle error
+                    Snackbar.make(textView!!, response.toString(), Snackbar.LENGTH_LONG)
+                        .setBackgroundTint(resources.getColor(R.color.deep_orange_darken_4))
+                        .show()
+                    progressBar!!.visibility = View.GONE
+                }
+            }
+
+            override fun onFailure(call: Call<List<AudioGson>>, t: Throwable) {
+                Log.e(javaClass.name, "onFailure", t)
+
+                Log.e(javaClass.name, "t.getCause():", t.cause)
+
+                // Handle error
+                Snackbar.make(textView!!, t.cause.toString(), Snackbar.LENGTH_LONG)
+                    .setBackgroundTint(resources.getColor(R.color.deep_orange_darken_4))
+                    .show()
+                progressBar!!.visibility = View.GONE
+            }
+        })
+    }
+
+    private fun processResponseBody(audioGsons: List<AudioGson>) {
+        Log.i(javaClass.name, "processResponseBody")
+
+        val executorService = Executors.newSingleThreadExecutor()
+        executorService.execute(object : Runnable {
+            override fun run() {
+                Log.i(javaClass.name, "run")
+
+                val roomDb = RoomDb.getDatabase(context)
+                val audioDao = roomDb.audioDao()
+
+                // Empty the database table before downloading up-to-date content
+                audioDao.deleteAll()
+
+                // TODO: also delete corresponding audio files (only those that are no longer used)
+                for (audioGson in audioGsons) {
+                    Log.i(javaClass.name, "audioGson.getId(): " + audioGson.id)
+
+                    val audio = GsonToRoomConverter.getAudio(audioGson)
+
+                    // Check if the corresponding audio file has already been downloaded
+                    val audioFile = FileHelper.getAudioFile(audioGson, context)
+                    Log.i(javaClass.name, "audioFile: $audioFile")
+                    Log.i(javaClass.name, "audioFile.exists(): " + audioFile.exists())
+                    if (!audioFile.exists()) {
+                        // Download file bytes
+                        val baseApplication = activity!!.application as BaseApplication
+                        val downloadUrl = baseApplication.baseUrl + audioGson.bytesUrl
+                        Log.i(javaClass.name, "downloadUrl: $downloadUrl")
+                        val bytes = MultimediaDownloader.downloadFileBytes(downloadUrl)
+                        Log.i(javaClass.name, "bytes.length: " + bytes.size)
+
+                        // Store the downloaded file in the external storage directory
+                        try {
+                            val fileOutputStream = FileOutputStream(audioFile)
+                            fileOutputStream.write(bytes)
+                        } catch (e: FileNotFoundException) {
+                            Log.e(javaClass.name, null, e)
+                        } catch (e: IOException) {
+                            Log.e(javaClass.name, null, e)
+                        }
+                        Log.i(javaClass.name, "audioFile.exists(): " + audioFile.exists())
+                    }
+
+                    // Store the Audio in the database
+                    audioDao.insert(audio)
+                    Log.i(javaClass.name, "Stored Audio in database with ID " + audio.id)
+                }
+
+                // Update the UI
+                val audios = audioDao.loadAll()
+                Log.i(javaClass.name, "audios.size(): " + audios.size)
+                activity!!.runOnUiThread {
+                    textView!!.text = "audios.size(): " + audios.size
+                    Snackbar.make(textView!!, "audios.size(): " + audios.size, Snackbar.LENGTH_LONG)
+                        .show()
+                    progressBar!!.visibility = View.GONE
+                }
+            }
+        })
+    }
+}