fix: 🐛 Prevent Android recorder crash from stopping unstarted muxer

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 2.1.0 (#unreleased)
 
 - Feature [#468](https://github.com/SimformSolutionsPvtLtd/audio_waveforms/pull/468) - Add macOS support
+- Fixed [#482](https://github.com/SimformSolutionsPvtLtd/audio_waveforms/issues/482) - Prevent Android crash on stop by checking muxer state before stopping
 
 ## 2.0.2
 

android/src/main/kotlin/com/simform/audio_waveforms/AudioRecorder.kt

@@ -135,16 +135,22 @@ class AudioRecorder : PluginRegistry.RequestPermissionsResultListener {
             )
             wavEncoder?.start(result)
         } else {
-            commonEncoder.initCodec(recorderSettings = recorderSettings!!, result = result) {
-                recordingThread?.join()
-            }
+            commonEncoder.initCodec(recorderSettings = recorderSettings!!, result = result)
         }
         val buffer = ByteArray(bufferSize!!)
         recordingThread = Thread {
             while (recorderState == RecorderState.Recording || recorderState == RecorderState.Paused) {
                 if (recorderState == RecorderState.Recording) {
                     val read = audioRecord?.read(buffer, 0, buffer.size) ?: 0
 
+                    if (read < 0) {
+                        // Negative return is an AudioRecord error (e.g. ERROR_INVALID_OPERATION,
+                        // ERROR_DEAD_OBJECT). Reading again would keep failing, so stop cleanly.
+                        Log.e(LOG_TAG, "AudioRecord.read() error: $read")
+                        recorderState = RecorderState.Stopped
+                        break
+                    }
+
                     if (read > 0) {
                         val audioData = buffer.copyOf(read)
                         if (encoder?.encodeForWav == true) {
@@ -169,12 +175,15 @@ class AudioRecorder : PluginRegistry.RequestPermissionsResultListener {
 
     fun stop(result: Result) {
         try {
+            // Stop the read loop first, then unblock and join the recording thread so it
+            // can never call audioRecord.read() after the AudioRecord is released below.
+            recorderState = RecorderState.Stopped
             audioRecord?.stop()
+            recordingThread?.join()
+            recordingThread = null
             totalSamples = 0L
-            recorderState = RecorderState.Stopped
             if (encoder?.encodeForWav == true) {
                 wavEncoder?.stop(result)
-                recordingThread?.join()
                 sendRecordingResult(result)
             } else {
                 commonEncoder.setOnEncodingCompleted {

android/src/main/kotlin/com/simform/audio_waveforms/encoders/CommonEncoder.kt

@@ -406,7 +406,11 @@ class CommonEncoder {
         try {
             mediaCodec.stop()
             mediaCodec.release()
-            mediaMuxer?.stop()
+            // Only stop the muxer if it was actually started; stopping an unstarted muxer
+            // throws and triggers the native MPEG4Writer "track not started" crash.
+            if (isMuxerStarted) {
+                mediaMuxer?.stop()
+            }
             mediaMuxer?.release()
             outputStream.close()
             handlerThread.quitSafely()