优化

app/src/main/java/io/legado/app/App.kt

@@ -89,7 +89,8 @@ class App : Application() {
      */
     @RequiresApi(Build.VERSION_CODES.O)
     private fun createChannelId() {
-        val notificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
+        val notificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as? NotificationManager
+        notificationManager?.let {
             //用唯一的ID创建渠道对象
             val downloadChannel = NotificationChannel(
                 channelIdDownload,
@@ -124,6 +125,7 @@ class App : Application() {
             webChannel.setSound(null, null)
 
             //向notification manager 提交channel
-        notificationManager.createNotificationChannels(Arrays.asList(downloadChannel, readAloudChannel, webChannel))
+            it.createNotificationChannels(Arrays.asList(downloadChannel, readAloudChannel, webChannel))
+        }
     }
 }