Refactor DocumentPropertiesAsyncTaskLoader to Kotlin

app/src/main/java/app/grapheneos/pdfviewer/PdfViewer.java

@@ -491,7 +491,7 @@ private int getWebViewRelease() {
     @NonNull
     @Override
     public Loader<List<CharSequence>> onCreateLoader(int id, Bundle args) {
-        return new DocumentPropertiesAsyncTaskLoader(this, args.getString(KEY_PROPERTIES), mNumPages, mUri);
+        return new DocumentPropertiesAsyncTaskLoader(this, args.getString(KEY_PROPERTIES), mNumPages, mUri).asLoader();
     }
 
     @Override

app/src/main/java/app/grapheneos/pdfviewer/loader/DocumentPropertiesAsyncTaskLoader.kt

@@ -0,0 +1,33 @@
+package app.grapheneos.pdfviewer.loader
+
+import android.content.Context
+import android.net.Uri
+import androidx.loader.content.AsyncTaskLoader
+import androidx.loader.content.Loader
+
+class DocumentPropertiesAsyncTaskLoader(context: Context, private val mProperties: String, private val mNumPages: Int, private val mUri: Uri):
+    AsyncTaskLoader<List<CharSequence>>(context) {
+
+    companion object {
+        const val TAG = "DocumentPropertiesLoader"
+        const val ID = 1
+    }
+
+    //Workaround till PdfViewer is migrated to Kotlin
+    fun asLoader() = this as Loader<List<CharSequence>>
+
+    override fun onStartLoading() {
+        super.onStartLoading()
+        forceLoad()
+    }
+
+    override fun loadInBackground(): List<CharSequence> {
+        val loader = DocumentPropertiesLoader(
+            context,
+            mProperties,
+            mNumPages,
+            mUri
+        )
+        return loader.loadAsList()
+    }
+}