diff --git a/app/src/main/kotlin/org/koitharu/kotatsu/core/util/BufferedObserver.kt b/app/src/main/kotlin/org/koitharu/kotatsu/core/util/BufferedObserver.kt
deleted file mode 100644
index ccebce668..000000000
--- a/app/src/main/kotlin/org/koitharu/kotatsu/core/util/BufferedObserver.kt
+++ /dev/null
@@ -1,6 +0,0 @@
-package org.koitharu.kotatsu.core.util
-
-fun interface BufferedObserver<T> {
-
-	fun onChanged(t: T, previous: T?)
-}
diff --git a/app/src/main/kotlin/org/koitharu/kotatsu/core/util/FileUtil.java b/app/src/main/kotlin/org/koitharu/kotatsu/core/util/FileUtil.java
deleted file mode 100644
index 9bda23a7e..000000000
--- a/app/src/main/kotlin/org/koitharu/kotatsu/core/util/FileUtil.java
+++ /dev/null
@@ -1,117 +0,0 @@
-package org.koitharu.kotatsu.core.util;
-
-import android.annotation.TargetApi;
-import android.content.Context;
-import android.net.Uri;
-import android.os.Build;
-import android.os.storage.StorageManager;
-import android.os.storage.StorageVolume;
-import android.provider.DocumentsContract;
-
-import androidx.annotation.Nullable;
-
-import java.io.File;
-import java.lang.reflect.Array;
-import java.lang.reflect.Method;
-import java.util.List;
-
-public final class FileUtil {
-
-	private static final String PRIMARY_VOLUME_NAME = "primary";
-
-	@Nullable
-	public static String getFullPathFromTreeUri(@Nullable final Uri treeUri, Context con) {
-		if (treeUri == null) return null;
-		String volumePath = getVolumePath(getVolumeIdFromTreeUri(treeUri), con);
-		if (volumePath == null) return File.separator;
-		if (volumePath.endsWith(File.separator))
-			volumePath = volumePath.substring(0, volumePath.length() - 1);
-
-		String documentPath = getDocumentPathFromTreeUri(treeUri);
-		if (documentPath.endsWith(File.separator))
-			documentPath = documentPath.substring(0, documentPath.length() - 1);
-
-		if (documentPath.length() > 0) {
-			if (documentPath.startsWith(File.separator))
-				return volumePath + documentPath;
-			else
-				return volumePath + File.separator + documentPath;
-		} else return volumePath;
-	}
-
-
-	private static String getVolumePath(final String volumeId, Context context) {
-		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
-			return getVolumePathForAndroid11AndAbove(volumeId, context);
-		} else
-			return getVolumePathBeforeAndroid11(volumeId, context);
-	}
-
-
-	private static String getVolumePathBeforeAndroid11(final String volumeId, Context context) {
-		try {
-			StorageManager mStorageManager = (StorageManager) context.getSystemService(Context.STORAGE_SERVICE);
-			Class<?> storageVolumeClazz = Class.forName("android.os.storage.StorageVolume");
-			Method getVolumeList = mStorageManager.getClass().getMethod("getVolumeList");
-			Method getUuid = storageVolumeClazz.getMethod("getUuid");
-			Method getPath = storageVolumeClazz.getMethod("getPath");
-			Method isPrimary = storageVolumeClazz.getMethod("isPrimary");
-			Object result = getVolumeList.invoke(mStorageManager);
-
-			final int length = Array.getLength(result);
-			for (int i = 0; i < length; i++) {
-				Object storageVolumeElement = Array.get(result, i);
-				String uuid = (String) getUuid.invoke(storageVolumeElement);
-				Boolean primary = (Boolean) isPrimary.invoke(storageVolumeElement);
-
-				if (primary && PRIMARY_VOLUME_NAME.equals(volumeId))    // primary volume?
-					return (String) getPath.invoke(storageVolumeElement);
-
-				if (uuid != null && uuid.equals(volumeId))    // other volumes?
-					return (String) getPath.invoke(storageVolumeElement);
-			}
-			// not found.
-			return null;
-		} catch (Exception ex) {
-			return null;
-		}
-	}
-
-	@TargetApi(Build.VERSION_CODES.R)
-	private static String getVolumePathForAndroid11AndAbove(final String volumeId, Context context) {
-		try {
-			StorageManager mStorageManager = (StorageManager) context.getSystemService(Context.STORAGE_SERVICE);
-			List<StorageVolume> storageVolumes = mStorageManager.getStorageVolumes();
-			for (StorageVolume storageVolume : storageVolumes) {
-				// primary volume?
-				if (storageVolume.isPrimary() && PRIMARY_VOLUME_NAME.equals(volumeId))
-					return storageVolume.getDirectory().getPath();
-
-				// other volumes?
-				String uuid = storageVolume.getUuid();
-				if (uuid != null && uuid.equals(volumeId))
-					return storageVolume.getDirectory().getPath();
-
-			}
-			// not found.
-			return null;
-		} catch (Exception ex) {
-			return null;
-		}
-	}
-
-	private static String getVolumeIdFromTreeUri(final Uri treeUri) {
-		final String docId = DocumentsContract.getTreeDocumentId(treeUri);
-		final String[] split = docId.split(":");
-		if (split.length > 0) return split[0];
-		else return null;
-	}
-
-
-	private static String getDocumentPathFromTreeUri(final Uri treeUri) {
-		final String docId = DocumentsContract.getTreeDocumentId(treeUri);
-		final String[] split = docId.split(":");
-		if ((split.length >= 2) && (split[1] != null)) return split[1];
-		else return File.separator;
-	}
-}
diff --git a/app/src/main/kotlin/org/koitharu/kotatsu/details/ui/MangaDetailsAdapter.kt b/app/src/main/kotlin/org/koitharu/kotatsu/details/ui/MangaDetailsAdapter.kt
deleted file mode 100644
index 03cf1d76c..000000000
--- a/app/src/main/kotlin/org/koitharu/kotatsu/details/ui/MangaDetailsAdapter.kt
+++ /dev/null
@@ -1,16 +0,0 @@
-package org.koitharu.kotatsu.details.ui
-
-import androidx.fragment.app.Fragment
-import androidx.fragment.app.FragmentActivity
-import androidx.viewpager2.adapter.FragmentStateAdapter
-
-class MangaDetailsAdapter(activity: FragmentActivity) : FragmentStateAdapter(activity) {
-
-	override fun getItemCount() = 2
-
-	override fun createFragment(position: Int): Fragment = when (position) {
-		0 -> DetailsFragment()
-		1 -> ChaptersFragment()
-		else -> throw IndexOutOfBoundsException("No fragment for position $position")
-	}
-}
\ No newline at end of file