Manipulate MediaItems, Lists and Arrays in Kotlin

When developing media-rich Android applications, especially using ExoPlayer, you’ll often deal with MediaItems. These represent audio or video items that you want to play. Understanding how to manipulate these items and manage them using Kotlin collections is essential for building dynamic playlists and media queues.

This article covers:

• Creating MediaItems using the Builder pattern

   

   

• Adding and removing items from Kotlin lists
• Differences between arrays and lists in Kotlin
• Useful collection operations for working with media items

   

Creating MediaItem in Kotlin

The MediaItem class in ExoPlayer is built using the Builder pattern. Here’s how to create one:

val mediaItem = MediaItem.Builder()
    .setMediaId("media123")
    .setUri("https://example.com/media.mp4")
    .build()

You can also include optional metadata:

val mediaMetadata = MediaMetadata.Builder()
    .setTitle("Sample Video")
    .setArtist("Sample Artist")
    .build()

val mediaItem = MediaItem.Builder()
    .setMediaId("media123")
    .setUri("https://example.com/media.mp4")
    .setMediaMetadata(mediaMetadata)
    .build()

Using Lists to Manage MediaItems

Kotlin offers powerful support for managing collections, such as lists. Here’s how you can manage a playlist:

Creating a Mutable List

val mediaList: MutableList<MediaItem> = mutableListOf()

Adding Items

mediaList.add(mediaItem)

Adding Multiple Items

val secondItem = MediaItem.Builder()
    .setMediaId("media456")
    .setUri("https://example.com/media2.mp4")
    .build()

mediaList.addAll(listOf(mediaItem, secondItem))

Inserting at a Specific Index

mediaList.add(1, mediaItem) // Inserts at position 1

Removing Items

mediaList.remove(mediaItem) // By object
mediaList.removeAt(0)       // By index

Iterating Through the List

Kotlin supports various ways to iterate:

for (item in mediaList) {
    println(item.mediaMetadata?.title)
}

Or with forEach:

mediaList.forEach {
    println(it.mediaMetadata?.title)
}

Arrays vs Lists in Kotlin

Converting Between Array and List

val mediaArray = mediaList.toTypedArray()
val newList = mediaArray.toMutableList()

Advanced Collection Operations

Filtering

val filteredList = mediaList.filter { it.mediaMetadata?.title?.contains("Sample") == true }

Mapping

val titles = mediaList.map { it.mediaMetadata?.title ?: "Untitled" }

Sorting (by title)

val sortedList = mediaList.sortedBy { it.mediaMetadata?.title }

Conclusion

Working with MediaItems and Kotlin collections like List, MutableList, and Array is both flexible and powerful. Whether you’re creating a video playlist, podcast player, or a full-featured music app, understanding these fundamentals will help you build efficient and maintainable code.

FAQs

Q: Can I use a regular List to manage a playlist?
A: You can use List, but it’s immutable. Use MutableList if you plan to add/remove items dynamically.

Q: What is the difference between List and ArrayList in Kotlin?
A: ArrayList is a Java class. MutableList is Kotlin’s recommended abstraction which can be backed by ArrayList or other implementations.

Q: How do I clear all media items from a list?
A: Use mediaList.clear() if it is a MutableList.

Featured Code Snippet: Insert MediaItem Into List

val updatedMediaItems: MutableList<MediaItem> = mutableListOf()
val mediaItem = MediaItem.Builder()
    .setMediaId("id1")
    .setUri("https://example.com/video.mp4")
    .build()

updatedMediaItems.add(mediaItem)