[camera_avfoundation] Fix crash when restarting image stream after recording

packages/camera/camera_avfoundation/example/ios/RunnerTests/StreamingNilBufferTests.swift

@@ -0,0 +1,200 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import AVFoundation
+import XCTest
+
+@testable import camera_avfoundation
+
+// Import Objectice-C part of the implementation when SwiftPM is used.
+#if canImport(camera_avfoundation_objc)
+  import camera_avfoundation_objc
+#endif
+
+/// Helper function to create a sample buffer without an image buffer (nil)
+/// This simulates the condition that occurs right after recording stops
+private func createNilImageBufferSampleBuffer() -> CMSampleBuffer {
+  var blockBuffer: CMBlockBuffer?
+  CMBlockBufferCreateWithMemoryBlock(
+    allocator: kCFAllocatorDefault,
+    memoryBlock: nil,
+    blockLength: 100,
+    blockAllocator: kCFAllocatorDefault,
+    customBlockSource: nil,
+    offsetToData: 0,
+    dataLength: 100,
+    flags: kCMBlockBufferAssureMemoryNowFlag,
+    blockBufferOut: &blockBuffer)
+
+  var formatDescription: CMFormatDescription?
+  var basicDescription = AudioStreamBasicDescription(
+    mSampleRate: 44100,
+    mFormatID: kAudioFormatLinearPCM,
+    mFormatFlags: 0,
+    mBytesPerPacket: 1,
+    mFramesPerPacket: 1,
+    mBitsPerChannel: 16,
+    mChannelsPerFrame: 1,
+    mReserved: 0)
+
+  CMAudioFormatDescriptionCreate(
+    allocator: kCFAllocatorDefault,
+    asbd: &basicDescription,
+    layoutSize: 0,
+    layout: nil,
+    magicCookieSize: 0,
+    magicCookie: nil,
+    extensions: nil,
+    formatDescriptionOut: &formatDescription)
+
+  var timingInfo = CMSampleTimingInfo(
+    duration: CMTimeMake(value: 1, timescale: 44100),
+    presentationTimeStamp: CMTime.zero,
+    decodeTimeStamp: CMTime.invalid)
+
+  var sampleBuffer: CMSampleBuffer?
+  CMSampleBufferCreate(
+    allocator: kCFAllocatorDefault,
+    dataBuffer: blockBuffer,
+    dataReady: true,
+    makeDataReadyCallback: nil,
+    refcon: nil,
+    formatDescription: formatDescription,
+    sampleCount: 1,
+    sampleTimingEntryCount: 1,
+    sampleTimingArray: &timingInfo,
+    sampleSizeEntryCount: 0,
+    sampleSizeArray: nil,
+    sampleBufferOut: &sampleBuffer)
+
+  return sampleBuffer!
+}
+
+final class StreamingNilBufferTests: XCTestCase {
+  func testStreamingWithNilImageBuffer() {
+    let captureSessionQueue = DispatchQueue(label: "testing")
+    let configuration = CameraTestUtils.createTestCameraConfiguration()
+    configuration.captureSessionQueue = captureSessionQueue
+
+    let camera = CameraTestUtils.createTestCamera(configuration)
+    let testVideoOutput = camera.captureVideoOutput.avOutput
+    let testVideoConnection = CameraTestUtils.createTestConnection(testVideoOutput)
+
+    let handlerMock = MockImageStreamHandler()
+    var eventCallCount = 0
+
+    handlerMock.eventSinkStub = { event in
+      eventCallCount += 1
+    }
+
+    let finishStartStreamExpectation = expectation(description: "Finish startStream")
+    let messenger = MockFlutterBinaryMessenger()
+
+    camera.startImageStream(
+      with: messenger, imageStreamHandler: handlerMock,
+      completion: { _ in
+        finishStartStreamExpectation.fulfill()
+      })
+
+    waitForExpectations(timeout: 30, handler: nil)
+    waitForQueueRoundTrip(with: DispatchQueue.main)
+
+    XCTAssertEqual(camera.isStreamingImages, true)
+    XCTAssertEqual(camera.streamingPendingFramesCount, 0)
+
+    // Send a nil image buffer sample (simulating post-recording condition)
+    let nilBufferSample = createNilImageBufferSampleBuffer()
+    camera.captureOutput(testVideoOutput, didOutput: nilBufferSample, from: testVideoConnection)
+
+    // Verify that the frame count is still 0 (frame was skipped)
+    XCTAssertEqual(camera.streamingPendingFramesCount, 0)
+    XCTAssertEqual(eventCallCount, 0, "No events should be sent for nil image buffers")
+
+    // Send a valid sample buffer to ensure streaming still works
+    let validSample = CameraTestUtils.createTestSampleBuffer()
+    camera.captureOutput(testVideoOutput, didOutput: validSample, from: testVideoConnection)
+
+    // Wait a bit for async processing
+    waitForQueueRoundTrip(with: captureSessionQueue)
+    waitForQueueRoundTrip(with: DispatchQueue.main)
+
+    // Verify that the valid frame was processed
+    XCTAssertEqual(camera.streamingPendingFramesCount, 1)
+    XCTAssertEqual(eventCallCount, 1, "Valid frame should trigger an event")
+  }
+
+  func testStreamingWithMixedNilAndValidBuffers() {
+    let captureSessionQueue = DispatchQueue(label: "testing")
+    let configuration = CameraTestUtils.createTestCameraConfiguration()
+    configuration.captureSessionQueue = captureSessionQueue
+
+    let camera = CameraTestUtils.createTestCamera(configuration)
+    let testVideoOutput = camera.captureVideoOutput.avOutput
+    let testVideoConnection = CameraTestUtils.createTestConnection(testVideoOutput)
+
+    let handlerMock = MockImageStreamHandler()
+    var eventCallCount = 0
+
+    handlerMock.eventSinkStub = { event in
+      eventCallCount += 1
+    }
+
+    let finishStartStreamExpectation = expectation(description: "Finish startStream")
+    let messenger = MockFlutterBinaryMessenger()
+
+    camera.startImageStream(
+      with: messenger, imageStreamHandler: handlerMock,
+      completion: { _ in
+        finishStartStreamExpectation.fulfill()
+      })
+
+    waitForExpectations(timeout: 30, handler: nil)
+    waitForQueueRoundTrip(with: DispatchQueue.main)
+
+    // Send alternating nil and valid buffers
+    let nilBufferSample = createNilImageBufferSampleBuffer()
+    let validSample = CameraTestUtils.createTestSampleBuffer()
+
+    camera.captureOutput(testVideoOutput, didOutput: validSample, from: testVideoConnection)
+    camera.captureOutput(testVideoOutput, didOutput: nilBufferSample, from: testVideoConnection)
+    camera.captureOutput(testVideoOutput, didOutput: validSample, from: testVideoConnection)
+    camera.captureOutput(testVideoOutput, didOutput: nilBufferSample, from: testVideoConnection)
+    camera.captureOutput(testVideoOutput, didOutput: validSample, from: testVideoConnection)
+
+    // Wait for async processing
+    waitForQueueRoundTrip(with: captureSessionQueue)
+    waitForQueueRoundTrip(with: DispatchQueue.main)
+
+    // Only valid buffers should be processed
+    XCTAssertEqual(eventCallCount, 3, "Only valid frames should trigger events")
+  }
+}
+
+// Helper to wait for a dispatch queue to process pending operations
+private func waitForQueueRoundTrip(with queue: DispatchQueue) {
+  let expectation = XCTestExpectation(description: "Queue round trip")
+  queue.async {
+    expectation.fulfill()
+  }
+  wait(for: [expectation], timeout: 5.0)
+}
+
+// Mock class from StreamingTests.swift
+private class MockImageStreamHandler: FLTImageStreamHandler {
+  var eventSinkStub: ((Any?) -> Void)?
+
+  override var eventSink: FlutterEventSink? {
+    get {
+      if let stub = eventSinkStub {
+        return { event in
+          stub(event)
+        }
+      }
+      return nil
+    }
+    set {
+      eventSinkStub = newValue
+    }
+  }
+}

packages/camera/camera_avfoundation/ios/camera_avfoundation/Sources/camera_avfoundation/DefaultCamera.swift

@@ -276,7 +276,11 @@ final class DefaultCamera: FLTCam, Camera {
       {
         streamingPendingFramesCount += 1
 
-        let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)!
+        guard let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else {
+          // Skip this frame if pixelBuffer is nil (can happen right after recording stops)
+          streamingPendingFramesCount -= 1
+          return
+        }
         // Must lock base address before accessing the pixel data
         CVPixelBufferLockBaseAddress(pixelBuffer, .readOnly)