diff --git a/AnkiDroid/src/main/java/com/ichi2/libanki/Collection.kt b/AnkiDroid/src/main/java/com/ichi2/libanki/Collection.kt
index d0407eb7cd..7b5818a144 100644
--- a/AnkiDroid/src/main/java/com/ichi2/libanki/Collection.kt
+++ b/AnkiDroid/src/main/java/com/ichi2/libanki/Collection.kt
@@ -757,19 +757,19 @@ open class Collection(
      */
     @KotlinCleanup("Check CollectionTask<Int?, Int> - should be fine")
     @KotlinCleanup("change to ArrayList!")
-    fun genCards(nids: kotlin.collections.Collection<Long?>?, model: Model): ArrayList<Long>? {
+    fun genCards(nids: kotlin.collections.Collection<Long>, model: Model): ArrayList<Long>? {
         return genCards<CollectionTask<Int?, Int>>(Utils.collection2Array(nids), model)
     }
 
     fun <T> genCards(
-        nids: kotlin.collections.Collection<Long?>?,
+        nids: kotlin.collections.Collection<Long>,
         model: Model,
         task: T?
     ): ArrayList<Long>? where T : ProgressSender<Int?>?, T : CancelListener? {
         return genCards(Utils.collection2Array(nids), model, task)
     }
 
-    fun genCards(nids: kotlin.collections.Collection<Long?>?, mid: NoteTypeId): ArrayList<Long>? {
+    fun genCards(nids: kotlin.collections.Collection<Long>, mid: NoteTypeId): ArrayList<Long>? {
         return genCards(nids, models.get(mid)!!)
     }
 
@@ -789,7 +789,7 @@ open class Collection(
      */
     @JvmOverloads
     fun <T> genCards(
-        nids: LongArray?,
+        nids: LongArray,
         model: Model,
         task: T? = null
     ): ArrayList<Long>? where T : ProgressSender<Int?>?, T : CancelListener? {
@@ -1036,11 +1036,11 @@ open class Collection(
     }
 
     // NOT IN LIBANKI //
-    fun cardCount(vararg dids: Long?): Int {
+    fun cardCount(vararg dids: Long): Int {
         return db.queryScalar("SELECT count() FROM cards WHERE did IN " + Utils.ids2str(dids))
     }
 
-    fun isEmptyDeck(vararg dids: Long?): Boolean {
+    fun isEmptyDeck(vararg dids: Long): Boolean {
         return cardCount(*dids) == 0
     }
 
@@ -1080,7 +1080,7 @@ open class Collection(
         return rem
     }
 
-    fun emptyCardReport(cids: List<Long>?): String {
+    fun emptyCardReport(cids: List<Long>): String {
         val rep = StringBuilder()
         db.query(
             "select group_concat(ord+1), count(), flds from cards c, notes n " +
@@ -1122,7 +1122,7 @@ open class Collection(
     /** Update field checksums and sort cache, after find&replace, etc.
      * @param nids
      */
-    fun updateFieldCache(nids: kotlin.collections.Collection<Long>?) {
+    fun updateFieldCache(nids: kotlin.collections.Collection<Long>) {
         val snids = Utils.ids2str(nids)
         updateFieldCache(snids)
     }
@@ -1130,7 +1130,7 @@ open class Collection(
     /** Update field checksums and sort cache, after find&replace, etc.
      * @param nids
      */
-    fun updateFieldCache(nids: LongArray?) {
+    fun updateFieldCache(nids: LongArray) {
         val snids = Utils.ids2str(nids)
         updateFieldCache(snids)
     }
@@ -2307,7 +2307,7 @@ open class Collection(
     /**
      * Card Flags *****************************************************************************************************
      */
-    fun setUserFlag(flag: Int, cids: List<Long>?) {
+    fun setUserFlag(flag: Int, cids: List<Long>) {
         assert(0 <= flag && flag <= 7)
         db.execute(
             "update cards set flags = (flags & ~?) | ?, usn=?, mod=? where id in " + Utils.ids2str(
diff --git a/AnkiDroid/src/main/java/com/ichi2/libanki/importer/Anki2Importer.kt b/AnkiDroid/src/main/java/com/ichi2/libanki/importer/Anki2Importer.kt
index fb2f0f5c00..2c80d17ab4 100644
--- a/AnkiDroid/src/main/java/com/ichi2/libanki/importer/Anki2Importer.kt
+++ b/AnkiDroid/src/main/java/com/ichi2/libanki/importer/Anki2Importer.kt
@@ -719,7 +719,7 @@ open class Anki2Importer(col: Collection?, file: String) : Importer(col!!, file)
         return _mediaData(fname, dst.media.dir())
     }
 
-    private fun _writeDstMedia(fname: String?, data: BufferedInputStream) {
+    private fun _writeDstMedia(fname: String, data: BufferedInputStream) {
         try {
             val path = File(dst.media.dir(), Utils.nfcNormalized(fname)).absolutePath
             Utils.writeToFile(data, path)
diff --git a/AnkiDroid/src/main/java/com/ichi2/libanki/importer/NoteImporter.kt b/AnkiDroid/src/main/java/com/ichi2/libanki/importer/NoteImporter.kt
index e06087b03c..e551c0b97e 100644
--- a/AnkiDroid/src/main/java/com/ichi2/libanki/importer/NoteImporter.kt
+++ b/AnkiDroid/src/main/java/com/ichi2/libanki/importer/NoteImporter.kt
@@ -11,10 +11,7 @@ import com.ichi2.libanki.*
 import com.ichi2.libanki.template.ParsedNode
 import com.ichi2.libanki.utils.StringUtils
 import com.ichi2.libanki.utils.TimeManager
-import com.ichi2.utils.Assert
-import com.ichi2.utils.HashUtil
-import com.ichi2.utils.HtmlUtils
-import com.ichi2.utils.JSONObject
+import com.ichi2.utils.*
 
 // Ported from https://github.com/ankitects/anki/blob/50fdf9b03dec33c99a501f332306f378db5eb4ea/pylib/anki/importing/noteimp.py
 // Aside from 9f676dbe0b2ad9b87a3bf89d7735b4253abd440e, which allows empty notes.
@@ -37,6 +34,7 @@ open class NoteImporter(col: com.ichi2.libanki.Collection, file: String) : Impor
 
     /** _nextID in python  */
     private var mNextId: Long = 0
+    @KotlinCleanup("maybe lateinit/nonnull")
     private var mIds: ArrayList<Long>? = null
     private var mEmptyNotes = false
     private var mUpdateCount = 0
@@ -210,9 +208,9 @@ open class NoteImporter(col: com.ichi2.libanki.Collection, file: String) : Impor
         addNew(_new)
         addUpdates(updates)
         // make sure to update sflds, etc
-        mCol.updateFieldCache(mIds)
+        mCol.updateFieldCache(mIds!!)
         // generate cards
-        if (mCol.genCards(mIds, mModel)!!.isNotEmpty()) {
+        if (mCol.genCards(mIds!!, mModel)!!.isNotEmpty()) {
             this.log.add(0, getString(R.string.note_importer_empty_cards_found))
         }
 
diff --git a/AnkiDroid/src/main/java/com/ichi2/libanki/sched/BaseSched.kt b/AnkiDroid/src/main/java/com/ichi2/libanki/sched/BaseSched.kt
index 1da1c8ea00..f3d485ea2e 100644
--- a/AnkiDroid/src/main/java/com/ichi2/libanki/sched/BaseSched.kt
+++ b/AnkiDroid/src/main/java/com/ichi2/libanki/sched/BaseSched.kt
@@ -388,7 +388,7 @@ abstract class BaseSched(val col: Collection) {
             "end)"
     }
 
-    fun remFromDyn(cids: Iterable<Long>?) {
+    fun remFromDyn(cids: Iterable<Long>) {
         emptyDyn("id IN " + Utils.ids2str(cids) + " AND odid")
     }