Address review

packages/camera/camera_android_camerax/android/src/main/java/io/flutter/plugins/camerax/CameraAndroidCameraxPlugin.java

@@ -63,10 +63,9 @@ public void onDetachedFromEngine(@NonNull FlutterPluginBinding binding) {
 
   @Override
   public void onAttachedToActivity(@NonNull ActivityPluginBinding activityPluginBinding) {
-    CameraAndroidCameraxPlugin plugin = new CameraAndroidCameraxPlugin();
-    plugin.setUp(pluginBinding.getBinaryMessenger(), pluginBinding.getApplicationContext());
-    plugin.updateContext(pluginBinding.getApplicationContext());
-    plugin.processCameraProviderHostApi.setLifecycleOwner(
+    this.setUp(pluginBinding.getBinaryMessenger(), pluginBinding.getApplicationContext());
+    this.updateContext(pluginBinding.getApplicationContext());
+    this.processCameraProviderHostApi.setLifecycleOwner(
         (LifecycleOwner) activityPluginBinding.getActivity());
   }
 

packages/camera/camera_android_camerax/android/src/main/java/io/flutter/plugins/camerax/CameraInfoHostApiImpl.java

@@ -7,6 +7,7 @@
 import androidx.annotation.NonNull;
 import androidx.camera.core.CameraInfo;
 import io.flutter.plugins.camerax.GeneratedCameraXLibrary.CameraInfoHostApi;
+import java.util.Objects;
 
 public class CameraInfoHostApiImpl implements CameraInfoHostApi {
   private final InstanceManager instanceManager;
@@ -17,7 +18,8 @@ public CameraInfoHostApiImpl(InstanceManager instanceManager) {
 
   @Override
   public Long getSensorRotationDegrees(@NonNull Long identifier) {
-    CameraInfo cameraInfo = (CameraInfo) instanceManager.getInstance(identifier);
+    CameraInfo cameraInfo =
+        (CameraInfo) Objects.requireNonNull(instanceManager.getInstance(identifier));
     return Long.valueOf(cameraInfo.getSensorRotationDegrees());
   }
 }

packages/camera/camera_android_camerax/android/src/main/java/io/flutter/plugins/camerax/CameraSelectorHostApiImpl.java

@@ -12,6 +12,7 @@
 import io.flutter.plugins.camerax.GeneratedCameraXLibrary.CameraSelectorHostApi;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
 
 public class CameraSelectorHostApiImpl implements CameraSelectorHostApi {
   private final BinaryMessenger binaryMessenger;
@@ -41,13 +42,15 @@ public void create(@NonNull Long identifier, Long lensFacing) {
 
   @Override
   public List<Long> filter(@NonNull Long identifier, @NonNull List<Long> cameraInfoIds) {
-    CameraSelector cameraSelector = (CameraSelector) instanceManager.getInstance(identifier);
+    CameraSelector cameraSelector =
+        (CameraSelector) Objects.requireNonNull(instanceManager.getInstance(identifier));
     List<CameraInfo> cameraInfosForFilter = new ArrayList<CameraInfo>();
 
     for (Number cameraInfoAsNumber : cameraInfoIds) {
       Long cameraInfoId = cameraInfoAsNumber.longValue();
 
-      CameraInfo cameraInfo = (CameraInfo) instanceManager.getInstance(cameraInfoId);
+      CameraInfo cameraInfo =
+          (CameraInfo) Objects.requireNonNull(instanceManager.getInstance(cameraInfoId));
       cameraInfosForFilter.add(cameraInfo);
     }
 

packages/camera/camera_android_camerax/android/src/main/java/io/flutter/plugins/camerax/ProcessCameraProviderHostApiImpl.java

@@ -18,6 +18,7 @@
 import io.flutter.plugins.camerax.GeneratedCameraXLibrary.ProcessCameraProviderHostApi;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
 
 public class ProcessCameraProviderHostApiImpl implements ProcessCameraProviderHostApi {
   private final BinaryMessenger binaryMessenger;
@@ -78,7 +79,7 @@ public void getInstance(GeneratedCameraXLibrary.Result<Long> result) {
   @Override
   public List<Long> getAvailableCameraInfos(@NonNull Long identifier) {
     ProcessCameraProvider processCameraProvider =
-        (ProcessCameraProvider) instanceManager.getInstance(identifier);
+        (ProcessCameraProvider) Objects.requireNonNull(instanceManager.getInstance(identifier));
 
     List<CameraInfo> availableCameras = processCameraProvider.getAvailableCameraInfos();
     List<Long> availableCamerasIds = new ArrayList<Long>();
@@ -103,12 +104,16 @@ public Long bindToLifecycle(
       @NonNull Long cameraSelectorIdentifier,
       @NonNull List<Long> useCaseIds) {
     ProcessCameraProvider processCameraProvider =
-        (ProcessCameraProvider) instanceManager.getInstance(identifier);
+        (ProcessCameraProvider) Objects.requireNonNull(instanceManager.getInstance(identifier));
     CameraSelector cameraSelector =
-        (CameraSelector) instanceManager.getInstance(cameraSelectorIdentifier);
+        (CameraSelector)
+            Objects.requireNonNull(instanceManager.getInstance(cameraSelectorIdentifier));
     UseCase[] useCases = new UseCase[useCaseIds.size()];
     for (int i = 0; i < useCaseIds.size(); i++) {
-      useCases[i] = (UseCase) instanceManager.getInstance(((Number) useCaseIds.get(i)).longValue());
+      useCases[i] =
+          (UseCase)
+              Objects.requireNonNull(
+                  instanceManager.getInstance(((Number) useCaseIds.get(i)).longValue()));
     }
 
     Camera camera =
@@ -125,18 +130,21 @@ public Long bindToLifecycle(
   @Override
   public void unbind(@NonNull Long identifier, @NonNull List<Long> useCaseIds) {
     ProcessCameraProvider processCameraProvider =
-        (ProcessCameraProvider) instanceManager.getInstance(identifier);
+        (ProcessCameraProvider) Objects.requireNonNull(instanceManager.getInstance(identifier));
     UseCase[] useCases = new UseCase[useCaseIds.size()];
     for (int i = 0; i < useCaseIds.size(); i++) {
-      useCases[i] = (UseCase) instanceManager.getInstance(((Number) useCaseIds.get(i)).longValue());
+      useCases[i] =
+          (UseCase)
+              Objects.requireNonNull(
+                  instanceManager.getInstance(((Number) useCaseIds.get(i)).longValue()));
     }
     processCameraProvider.unbind(useCases);
   }
 
   @Override
   public void unbindAll(@NonNull Long identifier) {
     ProcessCameraProvider processCameraProvider =
-        (ProcessCameraProvider) instanceManager.getInstance(identifier);
+        (ProcessCameraProvider) Objects.requireNonNull(instanceManager.getInstance(identifier));
     processCameraProvider.unbindAll();
   }
 }

packages/camera/camera_android_camerax/android/src/test/java/io/flutter/plugins/camerax/CameraTest.java

@@ -15,13 +15,10 @@
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
-import org.junit.runner.RunWith;
 import org.mockito.Mock;
 import org.mockito.junit.MockitoJUnit;
 import org.mockito.junit.MockitoRule;
-import org.robolectric.RobolectricTestRunner;
 
-@RunWith(RobolectricTestRunner.class)
 public class CameraTest {
   @Rule public MockitoRule mockitoRule = MockitoJUnit.rule();
 
@@ -35,6 +32,11 @@ public void setUp() {
     testInstanceManager = InstanceManager.open(identifier -> {});
   }
 
+  @After
+  public void tearDown() {
+    testInstanceManager.close();
+  }
+
   @Test
   public void flutterApiCreateTest() {
     final CameraFlutterApiImpl spyFlutterApi =

packages/camera/camera_android_camerax/lib/src/process_camera_provider.dart

@@ -95,11 +95,9 @@ class ProcessCameraProviderHostApiImpl extends ProcessCameraProviderHostApi {
   /// the [ProcessCameraProvider] instance.
   int getProcessCameraProviderIdentifier(ProcessCameraProvider instance) {
     int? identifier = instanceManager.getIdentifier(instance);
-    identifier ??= instanceManager.addDartCreatedInstance(instance,
-        onCopy: (ProcessCameraProvider original) {
-      return ProcessCameraProvider.detached(
-          binaryMessenger: binaryMessenger, instanceManager: instanceManager);
-    });
+
+    assert(identifier != null,
+        'No ProcessCameraProvider has the identifer of that requested.');
     return identifier;
   }