Allow switching between back and front camera

android/build.gradle

@@ -2,7 +2,7 @@ group 'com.u0x48lab.body_detection'
 version '1.0-SNAPSHOT'
 
 buildscript {
-    ext.kotlin_version = '1.3.50'
+    ext.kotlin_version = '1.6.20'
     repositories {
         google()
         mavenCentral()

android/src/main/kotlin/com/u0x48lab/body_detection/BodyDetectionPlugin.kt

@@ -5,6 +5,7 @@ import android.content.Context
 import android.graphics.Bitmap
 import android.graphics.BitmapFactory
 import androidx.annotation.NonNull
+import androidx.camera.core.CameraSelector
 import androidx.camera.core.ImageProxy
 import com.google.android.gms.tasks.OnFailureListener
 import com.google.android.gms.tasks.OnSuccessListener
@@ -25,6 +26,7 @@ class BodyDetectionPlugin: FlutterPlugin, MethodChannel.MethodCallHandler, Event
   private var poseDetectionEnabled = false
   private var bodyMaskDetectionEnabled = false
   private val poseDetector = MLKitPoseDetector(true)
+  private var lensFacing = CameraSelector.LENS_FACING_FRONT
   private val selfieSegmenter = MLKitSelfieSegmenter()
 
   override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
@@ -78,7 +80,7 @@ class BodyDetectionPlugin: FlutterPlugin, MethodChannel.MethodCallHandler, Event
         result.success(null)
       }
       "startCameraStream" -> {
-        val session = CameraSession(context)
+        val session = CameraSession(context, lensFacing)
         session.start { imageProxy, rotationDegrees ->
           handleCameraFrame(imageProxy, rotationDegrees)
         }
@@ -90,13 +92,19 @@ class BodyDetectionPlugin: FlutterPlugin, MethodChannel.MethodCallHandler, Event
         cameraSession = null
         result.success(true)
       }
+      "switchCamera" -> {
+        val isFront = call.argument("lensFacing") as String?
+        lensFacing =
+          if (isFront?.equals("FRONT") == true) CameraSelector.LENS_FACING_BACK else CameraSelector.LENS_FACING_BACK
+        result.success(true)
+      }
       else -> {
         result.notImplemented()
       }
     }
   }
 
-  @SuppressLint("UnsafeExperimentalUsageError")
+  @SuppressLint("UnsafeExperimentalUsageError", "UnsafeOptInUsageError")
   private fun handleCameraFrame(imageProxy: ImageProxy, rotationDegrees: Int) {
     val bitmap = BitmapUtils.getBitmap(imageProxy, true)
     val width = bitmap?.width ?: 0

android/src/main/kotlin/com/u0x48lab/body_detection/CameraSession.kt

@@ -13,18 +13,17 @@ import androidx.lifecycle.LifecycleOwner
 import androidx.lifecycle.LifecycleRegistry
 import java.util.concurrent.ExecutionException
 
-class CameraSession(private var context: Context) {
+class CameraSession(private var context: Context, private var lensFacing: Int) {
     private var processOutput: ((ImageProxy, Int) -> Unit)? = null
     private var cameraProvider: ProcessCameraProvider? = null
     private var analysisUseCase: ImageAnalysis? = null
-    private var lensFacing = CameraSelector.LENS_FACING_FRONT
-    private var cameraSelector = CameraSelector.DEFAULT_FRONT_CAMERA
+    private var cameraSelector = CameraSelector.Builder().requireLensFacing(lensFacing).build()
     private val lifecycle = CustomLifecycle()
 
     init {
         val cameraProviderFuture = ProcessCameraProvider.getInstance(context)
         cameraProviderFuture.addListener(
-            Runnable {
+            {
                 try {
                     cameraProvider = cameraProviderFuture.get()
 
@@ -94,6 +93,7 @@ class CameraSession(private var context: Context) {
 
         if (analysisUseCase != null) {
             cameraProvider!!.unbind(analysisUseCase)
+            analysisUseCase = null
         }
     }
 
@@ -108,13 +108,12 @@ class CameraSession(private var context: Context) {
         val useCase = builder.build()
 
         useCase.setAnalyzer(
-            ContextCompat.getMainExecutor(context),
-            ImageAnalysis.Analyzer { imageProxy: ImageProxy ->
-                val isImageFlipped = lensFacing == CameraSelector.LENS_FACING_FRONT
-                val rotationDegrees = imageProxy.imageInfo.rotationDegrees
-                processOutput?.let { it(imageProxy, rotationDegrees) }
-            }
-        )
+            ContextCompat.getMainExecutor(context)
+        ) { imageProxy: ImageProxy ->
+            val isImageFlipped = lensFacing == CameraSelector.LENS_FACING_FRONT
+            val rotationDegrees = imageProxy.imageInfo.rotationDegrees
+            processOutput?.let { it(imageProxy, rotationDegrees) }
+        }
 
         cameraProvider!!.bindToLifecycle(lifecycle, cameraSelector, useCase)
 

example/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.3.50'
+    ext.kotlin_version = '1.6.20'
     repositories {
         google()
         mavenCentral()

example/lib/main.dart

@@ -30,6 +30,7 @@ class _MyAppState extends State<MyApp> {
 
   bool _isDetectingPose = false;
   bool _isDetectingBodyMask = false;
+  LensFacing _lens = LensFacing.back;
 
   Image? _selectedImage;
 
@@ -164,6 +165,18 @@ class _MyAppState extends State<MyApp> {
     });
   }
 
+  Future<void> _toggleLens() async {
+    await _stopCameraStream();
+    if (_lens == LensFacing.front) {
+      await BodyDetection.switchCamera(LensFacing.back);
+      _lens = LensFacing.back;
+    } else {
+      await BodyDetection.switchCamera(LensFacing.front);
+      _lens = LensFacing.front;
+    }
+    await _startCameraStream();
+  }
+
   Future<void> _toggleDetectBodyMask() async {
     if (_isDetectingBodyMask) {
       await BodyDetection.disableBodyMaskDetection();
@@ -271,6 +284,12 @@ class _MyAppState extends State<MyApp> {
                     ? const Text('Turn off pose detection')
                     : const Text('Turn on pose detection'),
               ),
+              OutlinedButton(
+                onPressed: _toggleLens,
+                child: _lens == LensFacing.front
+                    ? const Text('Switch to back camera')
+                    : const Text('Switch to front camera'),
+              ),
               OutlinedButton(
                 onPressed: _toggleDetectBodyMask,
                 child: _isDetectingBodyMask

ios/Classes/CameraSession.swift

@@ -28,9 +28,10 @@ public class CameraSession: NSObject {
     private var isUsingFrontCamera = true
     private var processOutput: ((CMSampleBuffer, UIImage.Orientation) -> Void)?
 
-    public override init() {
+    public init(isUsingFrontCamera: Bool) {
         super.init()
-
+
+        self.isUsingFrontCamera = isUsingFrontCamera
         self.setUpCaptureSessionOutput()
         self.setUpCaptureSessionInput()
     }

ios/Classes/SwiftBodyDetectionPlugin.swift

@@ -7,6 +7,7 @@ public class SwiftBodyDetectionPlugin: NSObject, FlutterPlugin {
     private var cameraSession: CameraSession?
     private var poseDetectionEnabled = false
     private var bodyMaskDetectionEnabled = false
+    private var isUsingFrontCamera = true
     private let poseDetector = MLKitPoseDetector(stream: true)
     private let selfieSegmenter = MLKitSelfieSegmenter()
 
@@ -126,7 +127,7 @@ public class SwiftBodyDetectionPlugin: NSObject, FlutterPlugin {
                 print("Camera session already active! Call stopCameraStream first and try again.")
                 return
             }
-            let session = CameraSession()
+            let session = CameraSession(isUsingFrontCamera: isUsingFrontCamera)
             session.start(closure: self.handleCameraFrame)
             self.cameraSession = session
             result(true)
@@ -142,6 +143,20 @@ public class SwiftBodyDetectionPlugin: NSObject, FlutterPlugin {
             self.cameraSession = nil
             result(true)
             return
+        case "switchCamera":
+            do {
+                guard let arguments = call.arguments as? [String : Any] else {
+                    throw BodyDetectionPluginError.badArgument("Expected dictionary type.")
+                }
+                guard let lensFacing = arguments["lensFacing"] as? NSString else {
+                    throw BodyDetectionPluginError.badArgument("lensFacing")
+                }
+                isUsingFrontCamera = lensFacing == "FRONT"
+                result(true)
+            } catch {
+                result(error.toFlutterError());
+            }
+            return
 
         // Method not implemented.
         default:

lib/body_detection.dart

@@ -10,6 +10,11 @@ import 'models/body_mask.dart';
 import 'png_image.dart';
 import 'types.dart';
 
+enum LensFacing {
+  front,
+  back,
+}
+
 class BodyDetection {
   static const MethodChannel _channel =
       MethodChannel('com.0x48lab/body_detection');
@@ -99,6 +104,16 @@ class BodyDetection {
     }
   }
 
+  static Future<void> switchCamera(LensFacing facing) async {
+    try {
+      await _channel.invokeMethod<void>('switchCamera', <String, dynamic>{
+        'lensFacing': facing == LensFacing.front ? "FRONT" : "BACK",
+      });
+    } on PlatformException catch (e) {
+      throw BodyDetectionException(e.code, e.message);
+    }
+  }
+
   static Future<void> enablePoseDetection() async {
     try {
       await _channel.invokeMethod<void>('enablePoseDetection');