获取活跃AudioSession ID：Visualizer类可视化第三方音频遇阻

Hey there, I feel your pain—trying to get the Visualizer working with Spotify or other third-party apps can be tricky now that the old session ID 0 method is deprecated. Let’s break down how to handle this depending on your target Android version:

For Android 9 (API 28) and Below #

Before API 29, you could still access mixed audio output or grab active audio session IDs from other apps, but you need the right permissions and setup:

• First, add the RECORD_AUDIO permission to your manifest:

  <uses-permission android:name="android.permission.RECORD_AUDIO" />
  

• To fetch the active audio session ID from a third-party app, use AudioManager to query active playback sessions:

  val audioManager = getSystemService(Context.AUDIO_SERVICE) as AudioManager
  val activeSessions = audioManager.getActiveAudioPlaybackSessions()
  
  for (session in activeSessions) {
      // Skip your app's own sessions to target third-party apps like Spotify
      if (session.packageName != packageName) {
          val sessionId = session.id
          // Initialize Visualizer with this third-party session ID
          val visualizer = Visualizer(sessionId)
          // Configure your Visualizer callbacks and settings here
          break
      }
  }
  

  Note: This method isn’t 100% reliable across all apps and is restricted starting from API 29.

For Android 10 (API 29) and Above #

Due to privacy restrictions, accessing other apps’ audio session IDs directly is no longer allowed. Instead, you need to use the MediaProjection API to capture system-wide audio, then process that data for visualization:

1. Request MediaProjection Permission:
   Prompt the user to grant permission to capture screen and audio:

   private val REQUEST_CODE_MEDIA_PROJECTION = 101
   val mediaProjectionManager = getSystemService(Context.MEDIA_PROJECTION_SERVICE) as MediaProjectionManager
   val intent = mediaProjectionManager.createScreenCaptureIntent()
   startActivityForResult(intent, REQUEST_CODE_MEDIA_PROJECTION)
   

2. Handle Permission Result:
   Once the user approves, create a MediaProjection instance and set up audio capture:

   override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
       super.onActivityResult(requestCode, resultCode, data)
       if (requestCode == REQUEST_CODE_MEDIA_PROJECTION && resultCode == RESULT_OK) {
           val mediaProjection = mediaProjectionManager.getMediaProjection(resultCode, data!!)
           
           // Configure audio format for capture
           val audioFormat = AudioFormat.Builder()
               .setEncoding(AudioFormat.ENCODING_PCM_16BIT)
               .setSampleRate(44100)
               .setChannelMask(AudioFormat.CHANNEL_IN_MONO)
               .build()
           
           // Initialize AudioRecord with MediaProjection
           val bufferSize = AudioRecord.getMinBufferSize(44100, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT)
           val audioRecord = AudioRecord.Builder()
               .setAudioSource(MediaRecorder.AudioSource.REMOTE_SUBMIX)
               .setAudioFormat(audioFormat)
               .setBufferSizeInBytes(bufferSize)
               .setMediaProjection(mediaProjection)
               .build()
           
           // Start capturing audio in a background thread
           audioRecord.startRecording()
           // Read PCM data and compute FFT manually for visualization (replace Visualizer class logic)
       }
   }
   

3. Manual Visualization Logic:
   Since you can’t use the Visualizer class directly here, you’ll need to compute the frequency spectrum yourself from the captured PCM data. Use an FFT implementation (custom or a lightweight library) to convert time-domain PCM data into frequency-domain data for your visualizer UI.

Key Notes #

• Permissions: Ensure you request RECORD_AUDIO and handle foreground service requirements if your app needs to run in the background (newer Android versions restrict background audio capture).
• Visualizer Class Limitation: The Visualizer class now primarily works with your app’s own audio sessions. For third-party apps, MediaProjection is the official, supported approach.

I hope this helps you get your audio visualization up and running with Spotify and other apps! Let me know if you hit any specific roadblocks.

内容的提问来源于stack exchange，提问作者DoktorMerlin