Remove !! operators

app/src/main/java/com/example/android/uamp/viewmodels/MediaItemFragmentViewModel.kt

@@ -16,6 +16,7 @@
 
 package com.example.android.uamp.viewmodels
 
+import android.net.Uri
 import android.support.v4.media.MediaBrowserCompat
 import android.support.v4.media.MediaBrowserCompat.MediaItem
 import android.support.v4.media.MediaBrowserCompat.SubscriptionCallback
@@ -61,12 +62,12 @@ class MediaItemFragmentViewModel(
             val itemsList = children.map { child ->
                 val subtitle = child.description.subtitle ?: ""
                 MediaItemData(
-                    child.mediaId!!,
+                    child.mediaId.orEmpty(),
                     child.description.title.toString(),
                     subtitle.toString(),
-                    child.description.iconUri!!,
+                    child.description.iconUri ?: Uri.EMPTY,
                     child.isBrowsable,
-                    getResourceForMediaId(child.mediaId!!)
+                    getResourceForMediaId(child.mediaId.orEmpty())
                 )
             }
             _mediaItems.postValue(itemsList)

app/src/main/java/com/example/android/uamp/viewmodels/NowPlayingFragmentViewModel.kt

@@ -170,7 +170,7 @@ class NowPlayingFragmentViewModel(
         // Only update media item once we have duration available
         if (mediaMetadata.duration != 0L && mediaMetadata.id != null) {
             val nowPlayingMetadata = NowPlayingMetadata(
-                mediaMetadata.id!!,
+                mediaMetadata.id.orEmpty(),
                 mediaMetadata.albumArtUri,
                 mediaMetadata.title?.trim(),
                 mediaMetadata.displaySubtitle?.trim(),

automotive/src/main/java/com/example/android/uamp/automotive/UsernameAndPasswordSignInFragment.kt

@@ -88,7 +88,7 @@ class UsernameAndPasswordSignInFragment : Fragment() {
 
         submitButton.text = getString(R.string.sign_in_submit_button_label)
         submitButton.setOnClickListener {
-            onSignIn(userId!!, passwordInput.text.toString())
+            onSignIn(userId.orEmpty(), passwordInput.text.toString())
         }
     }
 

common/src/main/java/com/example/android/uamp/media/CastMediaItemConverter.kt

@@ -53,7 +53,7 @@ internal class CastMediaItemConverter : MediaItemConverter {
         mediaItem.mediaMetadata.discNumber?.let {
             castMediaMetadata.putInt(MediaMetadata.KEY_DISC_NUMBER, it)
         }
-        val mediaInfo = MediaInfo.Builder(mediaItem.localConfiguration!!.uri.toString())
+        val mediaInfo = MediaInfo.Builder(mediaItem.localConfiguration?.uri.toString())
             .setStreamType(MediaInfo.STREAM_TYPE_BUFFERED)
             .setContentType(MimeTypes.AUDIO_MPEG)
         mediaItem.localConfiguration?.let {

common/src/main/java/com/example/android/uamp/media/MusicService.kt

@@ -217,7 +217,11 @@ open class MusicService : MediaBrowserServiceCompat() {
 
         switchToPlayer(
             previousPlayer = null,
-            newPlayer = if (castPlayer?.isCastSessionAvailable == true) castPlayer!! else exoPlayer
+            newPlayer = if (castPlayer?.isCastSessionAvailable == true) {
+                castPlayer ?: exoPlayer
+            } else {
+                exoPlayer
+            }
         )
         notificationManager.showNotificationForPlayer(currentPlayer)
 
@@ -445,7 +449,7 @@ open class MusicService : MediaBrowserServiceCompat() {
          * remote Cast receiver rather than play audio locally.
          */
         override fun onCastSessionAvailable() {
-            switchToPlayer(currentPlayer, castPlayer!!)
+            castPlayer?.let { switchToPlayer(currentPlayer, it) }
         }
 
         /**
@@ -484,7 +488,7 @@ open class MusicService : MediaBrowserServiceCompat() {
         override fun onPrepare(playWhenReady: Boolean) {
             val recentSong = storage.loadRecentSong() ?: return
             onPrepareFromMediaId(
-                recentSong.mediaId!!,
+                recentSong.mediaId.orEmpty(),
                 playWhenReady,
                 recentSong.description.extras
             )

common/src/main/java/com/example/android/uamp/media/library/BrowseTree.kt

@@ -147,7 +147,7 @@ class BrowseTree(
 
         // Insert the album's root with an empty list for its children, and return the list.
         return mutableListOf<MediaMetadataCompat>().also {
-            mediaIdToChildren[albumMetadata.id!!] = it
+            mediaIdToChildren[albumMetadata.id.orEmpty()] = it
         }
     }
 }