KMP iOS AVAudioPlayer NPE

December 30, 2024

What's inside this article ⌄

Kotlin Multiplatform AudioPlayer null
IOS AVAudioPlayer npe error
KMP IOS audio player crash
Fix AVAudioPlayer null error

If you’re trying to play some sound on the IOS device using KMP, and face NPE while trying to instantiate the AVAudioPlayer instance, you may want to do it another way:

Have designated AVAudioEngine for the sound play operation
Configure AVAudioSession if you have multiple AVAudioEngines (as we already discussed here)
Create AVAudioPlayerNode and attach to our playback engine
Play sound on AVAudioPlayerNode

The code will be as follows:

private var playbackEngine: AVAudioEngine = AVAudioEngine()
private val playerNode = AVAudioPlayerNode()

init {
    setupAudioSession()
    setupPlaybackEngine()
}

private fun setupAudioSession() {
    val audioSession = AVAudioSession.sharedInstance()
    try {
        audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord, null)
        audioSession.setActive(true, null)
    } catch (e: Exception) {
        println("Failed to set audio session category: ${e.message}")
    }
}

private fun setupPlaybackEngine() {
    playbackEngine.attachNode(playerNode)
    playbackEngine.connect(playerNode, playbackEngine.mainMixerNode, null)
    playbackEngine.prepare()
    try {
        playbackEngine.startAndReturnError(null)
    } catch (e: Exception) {
        println("Failed to start playback engine: ${e.message}")
    }
}

fun playAudio(audioBuffer: AVAudioPCMBuffer) {
    playerNode.scheduleBuffer(audioBuffer, null)
    playerNode.play()
}