diff --git a/Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/fragments/CustomFilePickerFragment.java b/Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/fragments/CustomFilePickerFragment.java
deleted file mode 100644
index 933b4ad2ff..0000000000
--- a/Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/fragments/CustomFilePickerFragment.java
+++ /dev/null
@@ -1,90 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-or-later
-
-package org.dolphinemu.dolphinemu.fragments;
-
-import android.net.Uri;
-import android.os.Bundle;
-import android.view.View;
-import android.widget.TextView;
-
-import androidx.annotation.NonNull;
-import androidx.core.content.FileProvider;
-
-import com.nononsenseapps.filepicker.FilePickerFragment;
-
-import org.dolphinemu.dolphinemu.R;
-
-import java.io.File;
-import java.util.HashSet;
-
-public class CustomFilePickerFragment extends FilePickerFragment
-{
-  public static final String KEY_EXTENSIONS = "KEY_EXTENSIONS";
-
-  private HashSet<String> mExtensions;
-
-  public void setExtensions(HashSet<String> extensions)
-  {
-    Bundle b = getArguments();
-    if (b == null)
-      b = new Bundle();
-
-    b.putSerializable(KEY_EXTENSIONS, extensions);
-    setArguments(b);
-  }
-
-  @NonNull
-  @Override
-  public Uri toUri(@NonNull final File file)
-  {
-    return FileProvider
-            .getUriForFile(getContext(),
-                    getContext().getApplicationContext().getPackageName() + ".filesprovider",
-                    file);
-  }
-
-  @Override public void onActivityCreated(Bundle savedInstanceState)
-  {
-    super.onActivityCreated(savedInstanceState);
-
-    mExtensions = (HashSet<String>) getArguments().getSerializable(KEY_EXTENSIONS);
-
-    if (mode == MODE_DIR)
-    {
-      TextView ok = getActivity().findViewById(R.id.nnf_button_ok);
-      ok.setText(R.string.select_dir);
-
-      TextView cancel = getActivity().findViewById(R.id.nnf_button_cancel);
-      cancel.setVisibility(View.GONE);
-    }
-  }
-
-  @Override
-  protected boolean isItemVisible(@NonNull final File file)
-  {
-    // Some users jump to the conclusion that Dolphin isn't able to detect their
-    // files if the files don't show up in the file picker when mode == MODE_DIR.
-    // To avoid this, show files even when the user needs to select a directory.
-
-    return (showHiddenItems || !file.isHidden()) &&
-            (file.isDirectory() ||
-                    mExtensions.contains(fileExtension(file.getName()).toLowerCase()));
-  }
-
-  @Override
-  public boolean isCheckable(@NonNull final File file)
-  {
-    // We need to make a small correction to the isCheckable logic due to
-    // overriding isItemVisible to show files when mode == MODE_DIR.
-    // AbstractFilePickerFragment always treats files as checkable when
-    // allowExistingFile == true, but we don't want files to be checkable when mode == MODE_DIR.
-
-    return super.isCheckable(file) && !(mode == MODE_DIR && file.isFile());
-  }
-
-  private static String fileExtension(@NonNull String filename)
-  {
-    int i = filename.lastIndexOf('.');
-    return i < 0 ? "" : filename.substring(i + 1);
-  }
-}
diff --git a/Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/fragments/CustomFilePickerFragment.kt b/Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/fragments/CustomFilePickerFragment.kt
new file mode 100644
index 0000000000..aa74fb6f8a
--- /dev/null
+++ b/Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/fragments/CustomFilePickerFragment.kt
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package org.dolphinemu.dolphinemu.fragments
+
+import android.net.Uri
+import android.os.Bundle
+import android.view.View
+import android.widget.TextView
+import androidx.core.content.FileProvider
+import com.nononsenseapps.filepicker.FilePickerFragment
+import org.dolphinemu.dolphinemu.R
+import org.dolphinemu.dolphinemu.utils.SerializableHelper.serializable
+import java.io.File
+import java.util.Locale
+
+class CustomFilePickerFragment : FilePickerFragment() {
+    private var extensions: HashSet<String>? = null
+
+    fun setExtensions(extensions: HashSet<String>?) {
+        var b = arguments
+        if (b == null)
+            b = Bundle()
+        b.putSerializable(KEY_EXTENSIONS, extensions)
+        arguments = b
+    }
+
+    override fun toUri(file: File): Uri {
+        return FileProvider.getUriForFile(
+            requireContext(),
+            "${requireContext().applicationContext.packageName}.filesprovider",
+            file
+        )
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+
+        extensions = requireArguments().serializable(KEY_EXTENSIONS) as HashSet<String>?
+
+        if (mode == MODE_DIR) {
+            val ok = requireActivity().findViewById<TextView>(R.id.nnf_button_ok)
+            ok.setText(R.string.select_dir)
+
+            val cancel = requireActivity().findViewById<TextView>(R.id.nnf_button_cancel)
+            cancel.visibility = View.GONE
+        }
+    }
+
+    override fun isItemVisible(file: File): Boolean {
+        // Some users jump to the conclusion that Dolphin isn't able to detect their
+        // files if the files don't show up in the file picker when mode == MODE_DIR.
+        // To avoid this, show files even when the user needs to select a directory.
+        return (showHiddenItems || !file.isHidden) &&
+                (file.isDirectory || extensions!!.contains(fileExtension(file.name).lowercase(Locale.getDefault())))
+    }
+
+    override fun isCheckable(file: File): Boolean {
+        // We need to make a small correction to the isCheckable logic due to
+        // overriding isItemVisible to show files when mode == MODE_DIR.
+        // AbstractFilePickerFragment always treats files as checkable when
+        // allowExistingFile == true, but we don't want files to be checkable when mode == MODE_DIR.
+        return super.isCheckable(file) && !(mode == MODE_DIR && file.isFile)
+    }
+
+    companion object {
+        const val KEY_EXTENSIONS = "KEY_EXTENSIONS"
+
+        private fun fileExtension(filename: String): String {
+            val i = filename.lastIndexOf('.')
+            return if (i < 0) "" else filename.substring(i + 1)
+        }
+    }
+}