Convert LettersFragment from Java to Kotlin

app/src/main/java/ai/elimu/content_provider/ui/letter/LettersFragment.kt

@@ -0,0 +1,142 @@
+package ai.elimu.content_provider.ui.letter
+
+import ai.elimu.content_provider.BaseApplication
+import ai.elimu.content_provider.R
+import ai.elimu.content_provider.rest.LettersService
+import ai.elimu.content_provider.room.GsonToRoomConverter
+import ai.elimu.content_provider.room.db.RoomDb
+import ai.elimu.model.v2.gson.content.LetterGson
+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.util.concurrent.Executors
+
+class LettersFragment : Fragment() {
+    private var lettersViewModel: LettersViewModel? = null
+
+    private var progressBar: ProgressBar? = null
+
+    private var textView: TextView? = null
+
+    private val TAG = javaClass.name
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        Log.i(TAG, "onCreateView")
+
+        lettersViewModel = ViewModelProvider(this).get(
+            LettersViewModel::class.java
+        )
+        val root = inflater.inflate(R.layout.fragment_letters, container, false)
+        progressBar = root.findViewById(R.id.progress_bar_letters)
+        textView = root.findViewById(R.id.text_letters) as? TextView
+        lettersViewModel!!.text.observe(viewLifecycleOwner, object : Observer<String?> {
+            override fun onChanged(s: String?) {
+                Log.i(TAG, "onChanged")
+                textView?.text = s
+            }
+        })
+        return root
+    }
+
+    override fun onStart() {
+        Log.i(TAG, "onStart")
+        super.onStart()
+
+        // Download Letters from REST API, and store them in the database
+        val baseApplication = activity!!.application as BaseApplication
+        val retrofit = baseApplication.retrofit
+        val lettersService = retrofit.create(LettersService::class.java)
+        val letterGsonsCall = lettersService.listLetters()
+        Log.i(TAG, "letterGsonsCall.request(): " + letterGsonsCall.request())
+        letterGsonsCall.enqueue(object : Callback<List<LetterGson>> {
+            override fun onResponse(
+                call: Call<List<LetterGson>>,
+                response: Response<List<LetterGson>>
+            ) {
+                Log.i(TAG, "onResponse")
+
+                Log.i(TAG, "response: $response")
+                if (response.isSuccessful) {
+                    val letterGsons = response.body()!!
+                    Log.i(TAG, "letterGsons.size(): " + letterGsons.size)
+
+                    if (letterGsons.size > 0) {
+                        processResponseBody(letterGsons)
+                    }
+                } 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<LetterGson>>, t: Throwable) {
+                Log.e(TAG, "onFailure", t)
+
+                Log.e(TAG, "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(letterGsons: List<LetterGson>) {
+        Log.i(TAG, "processResponseBody")
+
+        val executorService = Executors.newSingleThreadExecutor()
+        executorService.execute(object : Runnable {
+            override fun run() {
+                Log.i(TAG, "run")
+
+                val roomDb = RoomDb.getDatabase(context)
+                val letterDao = roomDb.letterDao()
+
+                // Empty the database table before downloading up-to-date content
+                letterDao.deleteAll()
+
+                for (letterGson in letterGsons) {
+                    Log.i(TAG, "letterGson.getId(): " + letterGson.id)
+
+                    // Store the Letter in the database
+                    val letter = GsonToRoomConverter.getLetter(letterGson)
+                    letterDao.insert(letter)
+                    Log.i(TAG, "Stored Letter in database with ID " + letter.id)
+                }
+
+                // Update the UI
+                val letters = letterDao.loadAllOrderedByUsageCount()
+                Log.i(TAG, "letters.size(): " + letters.size)
+                activity!!.runOnUiThread {
+                    textView!!.text = "letters.size(): " + letters.size
+                    Snackbar.make(
+                        textView!!,
+                        "letters.size(): " + letters.size,
+                        Snackbar.LENGTH_LONG
+                    ).show()
+                    progressBar!!.visibility = View.GONE
+                }
+            }
+        })
+    }
+}