diff --git a/core/src/main/java/org/kiwix/kiwixmobile/core/di/modules/DialogModule.kt b/core/src/main/java/org/kiwix/kiwixmobile/core/di/modules/DialogModule.kt
index d9ad67405..c60954060 100644
--- a/core/src/main/java/org/kiwix/kiwixmobile/core/di/modules/DialogModule.kt
+++ b/core/src/main/java/org/kiwix/kiwixmobile/core/di/modules/DialogModule.kt
@@ -34,5 +34,5 @@ abstract class DialogModule {
   abstract fun bindDialogShower(alertDialogShower: AlertDialogShower): DialogShower
 
   @Binds
-  abstract fun bindMainPresenter(mainPresenter: MainPresenter): MainContract.Presenter
+  internal abstract fun bindMainPresenter(mainPresenter: MainPresenter): MainContract.Presenter
 }
diff --git a/core/src/main/java/org/kiwix/kiwixmobile/core/main/MainPresenter.java b/core/src/main/java/org/kiwix/kiwixmobile/core/main/MainPresenter.java
deleted file mode 100644
index d80fdc393..000000000
--- a/core/src/main/java/org/kiwix/kiwixmobile/core/main/MainPresenter.java
+++ /dev/null
@@ -1,153 +0,0 @@
-/*
- * Kiwix Android
- * Copyright (c) 2019 Kiwix <android.kiwix.org>
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program. If not, see <http://www.gnu.org/licenses/>.
- *
- */
-
-package org.kiwix.kiwixmobile.core.main;
-
-import android.util.Log;
-import io.reactivex.CompletableObserver;
-import io.reactivex.SingleObserver;
-import io.reactivex.disposables.Disposable;
-import java.util.List;
-import javax.inject.Inject;
-import org.kiwix.kiwixmobile.core.base.BasePresenter;
-import org.kiwix.kiwixmobile.core.bookmark.BookmarkItem;
-import org.kiwix.kiwixmobile.core.data.DataSource;
-import org.kiwix.kiwixmobile.core.di.ActivityScope;
-import org.kiwix.kiwixmobile.core.history.HistoryListItem;
-import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.adapter.BooksOnDiskListItem;
-
-/**
- * Presenter for {@link MainActivity}.
- */
-
-@ActivityScope
-public class MainPresenter extends BasePresenter<MainContract.View>
-  implements MainContract.Presenter {
-
-  private static final String TAG = "MainPresenter";
-  private final DataSource dataSource;
-
-  @Inject public MainPresenter(DataSource dataSource) {
-    this.dataSource = dataSource;
-  }
-
-  @Override
-  public void loadBooks() {
-    dataSource.getLanguageCategorizedBooks()
-      .subscribe(new SingleObserver<List<BooksOnDiskListItem>>() {
-        @Override
-        public void onSubscribe(Disposable d) {
-          compositeDisposable.add(d);
-        }
-
-        @Override
-        public void onSuccess(List<BooksOnDiskListItem> books) {
-          view.addBooks(books);
-        }
-
-        @Override
-        public void onError(Throwable e) {
-          Log.e(TAG, "Unable to load books", e);
-        }
-      });
-  }
-
-  @Override
-  public void saveBooks(List<BooksOnDiskListItem.BookOnDisk> book) {
-    dataSource.saveBooks(book)
-      .subscribe(new CompletableObserver() {
-        @Override
-        public void onSubscribe(Disposable d) {
-
-        }
-
-        @Override
-        public void onComplete() {
-          loadBooks();
-        }
-
-        @Override
-        public void onError(Throwable e) {
-          Log.e(TAG, "Unable to save books", e);
-        }
-      });
-  }
-
-  @Override
-  public void saveHistory(HistoryListItem.HistoryItem history) {
-    dataSource.saveHistory(history)
-      .subscribe(new CompletableObserver() {
-        @Override
-        public void onSubscribe(Disposable d) {
-
-        }
-
-        @Override
-        public void onComplete() {
-
-        }
-
-        @Override
-        public void onError(Throwable e) {
-          Log.e(TAG, "Unable to save history", e);
-        }
-      });
-  }
-
-  @Override
-  public void saveBookmark(BookmarkItem bookmark) {
-    dataSource.saveBookmark(bookmark)
-      .subscribe(new CompletableObserver() {
-        @Override
-        public void onSubscribe(Disposable d) {
-
-        }
-
-        @Override
-        public void onComplete() {
-
-        }
-
-        @Override
-        public void onError(Throwable e) {
-          Log.e(TAG, "Unable to save bookmark", e);
-        }
-      });
-  }
-
-  @Override
-  public void deleteBookmark(String bookmarkUrl) {
-    dataSource.deleteBookmark(bookmarkUrl)
-      .subscribe(new CompletableObserver() {
-        @Override
-        public void onSubscribe(Disposable d) {
-
-        }
-
-        @Override
-        public void onComplete() {
-
-        }
-
-        @Override
-        public void onError(Throwable e) {
-          Log.e(TAG, "Unable to delete bookmark", e);
-        }
-      });
-  }
-}
diff --git a/core/src/main/java/org/kiwix/kiwixmobile/core/main/MainPresenter.kt b/core/src/main/java/org/kiwix/kiwixmobile/core/main/MainPresenter.kt
new file mode 100644
index 000000000..a87f02de1
--- /dev/null
+++ b/core/src/main/java/org/kiwix/kiwixmobile/core/main/MainPresenter.kt
@@ -0,0 +1,62 @@
+/*
+ * Kiwix Android
+ * Copyright (c) 2019 Kiwix <android.kiwix.org>
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+package org.kiwix.kiwixmobile.core.main
+
+import android.util.Log
+import org.kiwix.kiwixmobile.core.base.BasePresenter
+import org.kiwix.kiwixmobile.core.bookmark.BookmarkItem
+import org.kiwix.kiwixmobile.core.data.DataSource
+import org.kiwix.kiwixmobile.core.di.ActivityScope
+import org.kiwix.kiwixmobile.core.history.HistoryListItem.HistoryItem
+import org.kiwix.kiwixmobile.core.main.MainContract.Presenter
+import org.kiwix.kiwixmobile.core.main.MainContract.View
+import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.adapter.BooksOnDiskListItem.BookOnDisk
+import javax.inject.Inject
+
+private const val TAG = "MainPresenter"
+
+@ActivityScope
+internal class MainPresenter @Inject constructor(private val dataSource: DataSource) :
+  BasePresenter<View?>(), Presenter {
+  override fun loadBooks() {
+    compositeDisposable.add(
+      dataSource.languageCategorizedBooks.subscribe(
+        view!!::addBooks
+      ) { e -> Log.e(TAG, "Unable to load books", e) })
+  }
+
+  override fun saveBooks(book: List<BookOnDisk>) {
+    dataSource.saveBooks(book)
+      .subscribe(::loadBooks) { e -> Log.e(TAG, "Unable to save books", e) }
+  }
+
+  override fun saveHistory(history: HistoryItem) {
+    dataSource.saveHistory(history)
+      .subscribe({}, { e -> Log.e(TAG, "Unable to save history", e) })
+  }
+
+  override fun saveBookmark(bookmark: BookmarkItem) {
+    dataSource.saveBookmark(bookmark)
+      .subscribe({}, { e -> Log.e(TAG, "Unable to save bookmark", e) })
+  }
+
+  override fun deleteBookmark(bookmarkUrl: String) {
+    dataSource.deleteBookmark(bookmarkUrl)
+      .subscribe({}, { e -> Log.e(TAG, "Unable to delete bookmark", e) })
+  }
+}