[camerax] Implements torch mode (flutter#4903)

Implements the torch flash mode. Also wraps classes necessary for the implementation (a method in `Camera`, `CameraControl`).

Fixes flutter/flutter#120715.
Fixes flutter/flutter#115846.
Part of flutter/flutter#115847.

packages/camera/camera_android_camerax/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.5.0+19
+
+* Implements torch flash mode.
+
 ## 0.5.0+18
 
 * Implements `startVideoCapturing`.

packages/camera/camera_android_camerax/README.md

@@ -35,10 +35,6 @@ and thus, the plugin will fall back to 480p if configured with a
 
 `lockCaptureOrientation` & `unLockCaptureOrientation` are unimplemented.
 
-### Torch mode \[[Issue #120715][120715]\]
-
-Calling `setFlashMode` with mode `FlashMode.torch` currently does nothing.
-
 ### Exposure mode, point, & offset configuration \[[Issue #120468][120468]\]
 
 `setExposureMode`, `setExposurePoint`, & `setExposureOffset` are unimplemented.

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

@@ -25,6 +25,7 @@ public final class CameraAndroidCameraxPlugin implements FlutterPlugin, Activity
   private VideoCaptureHostApiImpl videoCaptureHostApiImpl;
   private ImageAnalysisHostApiImpl imageAnalysisHostApiImpl;
   private ImageCaptureHostApiImpl imageCaptureHostApiImpl;
+  private CameraControlHostApiImpl cameraControlHostApiImpl;
   public @Nullable SystemServicesHostApiImpl systemServicesHostApiImpl;
 
   @VisibleForTesting
@@ -81,7 +82,8 @@ public void setUp(
     GeneratedCameraXLibrary.LiveDataHostApi.setup(binaryMessenger, liveDataHostApiImpl);
     GeneratedCameraXLibrary.ObserverHostApi.setup(
         binaryMessenger, new ObserverHostApiImpl(binaryMessenger, instanceManager));
-    imageAnalysisHostApiImpl = new ImageAnalysisHostApiImpl(binaryMessenger, instanceManager);
+    imageAnalysisHostApiImpl =
+        new ImageAnalysisHostApiImpl(binaryMessenger, instanceManager, context);
     GeneratedCameraXLibrary.ImageAnalysisHostApi.setup(binaryMessenger, imageAnalysisHostApiImpl);
     GeneratedCameraXLibrary.AnalyzerHostApi.setup(
         binaryMessenger, new AnalyzerHostApiImpl(binaryMessenger, instanceManager));
@@ -107,6 +109,8 @@ public void setUp(
         binaryMessenger, new FallbackStrategyHostApiImpl(instanceManager));
     GeneratedCameraXLibrary.QualitySelectorHostApi.setup(
         binaryMessenger, new QualitySelectorHostApiImpl(instanceManager));
+    cameraControlHostApiImpl = new CameraControlHostApiImpl(instanceManager, context);
+    GeneratedCameraXLibrary.CameraControlHostApi.setup(binaryMessenger, cameraControlHostApiImpl);
   }
 
   @Override
@@ -128,7 +132,6 @@ public void onAttachedToActivity(@NonNull ActivityPluginBinding activityPluginBi
     Activity activity = activityPluginBinding.getActivity();
 
     setUp(pluginBinding.getBinaryMessenger(), activity, pluginBinding.getTextureRegistry());
-    updateContext(activity);
 
     if (activity instanceof LifecycleOwner) {
       processCameraProviderHostApiImpl.setLifecycleOwner((LifecycleOwner) activity);
@@ -183,5 +186,8 @@ public void updateContext(@NonNull Context context) {
     if (imageAnalysisHostApiImpl != null) {
       imageAnalysisHostApiImpl.setContext(context);
     }
+    if (cameraControlHostApiImpl != null) {
+      cameraControlHostApiImpl.setContext(context);
+    }
   }
 }

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

@@ -0,0 +1,29 @@
+// 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.
+
+package io.flutter.plugins.camerax;
+
+import androidx.annotation.NonNull;
+import androidx.camera.core.CameraControl;
+import io.flutter.plugin.common.BinaryMessenger;
+import io.flutter.plugins.camerax.GeneratedCameraXLibrary.CameraControlFlutterApi;
+
+public class CameraControlFlutterApiImpl extends CameraControlFlutterApi {
+  private final @NonNull InstanceManager instanceManager;
+
+  public CameraControlFlutterApiImpl(
+      @NonNull BinaryMessenger binaryMessenger, @NonNull InstanceManager instanceManager) {
+    super(binaryMessenger);
+    this.instanceManager = instanceManager;
+  }
+
+  /**
+   * Creates a {@link CameraControl} instance in Dart. {@code reply} is not used so it can be empty.
+   */
+  void create(CameraControl cameraControl, Reply<Void> reply) {
+    if (!instanceManager.containsInstance(cameraControl)) {
+      create(instanceManager.addHostCreatedInstance(cameraControl), reply);
+    }
+  }
+}

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

@@ -0,0 +1,101 @@
+// 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.
+
+package io.flutter.plugins.camerax;
+
+import android.content.Context;
+import androidx.annotation.NonNull;
+import androidx.annotation.VisibleForTesting;
+import androidx.camera.core.CameraControl;
+import androidx.core.content.ContextCompat;
+import com.google.common.util.concurrent.FutureCallback;
+import com.google.common.util.concurrent.Futures;
+import com.google.common.util.concurrent.ListenableFuture;
+import io.flutter.plugins.camerax.GeneratedCameraXLibrary.CameraControlHostApi;
+import java.util.Objects;
+
+/**
+ * Host API implementation for {@link CameraControl}.
+ *
+ * <p>This class handles instantiating and adding native object instances that are attached to a
+ * Dart instance or handle method calls on the associated native class or an instance of the class.
+ */
+public class CameraControlHostApiImpl implements CameraControlHostApi {
+  private final InstanceManager instanceManager;
+  private final CameraControlProxy proxy;
+
+  /** Proxy for constructors and static method of {@link CameraControl}. */
+  @VisibleForTesting
+  public static class CameraControlProxy {
+    Context context;
+
+    /** Enables or disables the torch of the specified {@link CameraControl} instance. */
+    @NonNull
+    public void enableTorch(
+        @NonNull CameraControl cameraControl,
+        @NonNull Boolean torch,
+        @NonNull GeneratedCameraXLibrary.Result<Void> result) {
+      ListenableFuture<Void> enableTorchFuture = cameraControl.enableTorch(torch);
+
+      Futures.addCallback(
+          enableTorchFuture,
+          new FutureCallback<Void>() {
+            public void onSuccess(Void voidResult) {
+              result.success(null);
+            }
+
+            public void onFailure(Throwable t) {
+              result.error(t);
+            }
+          },
+          ContextCompat.getMainExecutor(context));
+    }
+  }
+
+  /**
+   * Constructs an {@link CameraControlHostApiImpl}.
+   *
+   * @param instanceManager maintains instances stored to communicate with attached Dart objects
+   */
+  public CameraControlHostApiImpl(
+      @NonNull InstanceManager instanceManager, @NonNull Context context) {
+    this(instanceManager, new CameraControlProxy(), context);
+  }
+
+  /**
+   * Constructs an {@link CameraControlHostApiImpl}.
+   *
+   * @param instanceManager maintains instances stored to communicate with attached Dart objects
+   * @param proxy proxy for constructors and static method of {@link CameraControl}
+   * @param context {@link Context} used to retrieve {@code Executor} used to enable torch mode
+   */
+  @VisibleForTesting
+  CameraControlHostApiImpl(
+      @NonNull InstanceManager instanceManager,
+      @NonNull CameraControlProxy proxy,
+      @NonNull Context context) {
+    this.instanceManager = instanceManager;
+    this.proxy = proxy;
+    proxy.context = context;
+  }
+
+  /**
+   * Sets the context that the {@code ProcessCameraProvider} will use to enable/disable torch mode.
+   *
+   * <p>If using the camera plugin in an add-to-app context, ensure that a new instance of the
+   * {@code CameraControl} is fetched via {@code #enableTorch} anytime the context changes.
+   */
+  public void setContext(@NonNull Context context) {
+    this.proxy.context = context;
+  }
+
+  @Override
+  public void enableTorch(
+      @NonNull Long identifier,
+      @NonNull Boolean torch,
+      @NonNull GeneratedCameraXLibrary.Result<Void> result) {
+    proxy.enableTorch(
+        Objects.requireNonNull(instanceManager.getInstance(identifier)), torch, result);
+  }
+}

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

@@ -6,6 +6,7 @@
 
 import androidx.annotation.NonNull;
 import androidx.camera.core.Camera;
+import androidx.camera.core.CameraControl;
 import androidx.camera.core.CameraInfo;
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugins.camerax.GeneratedCameraXLibrary.CameraHostApi;
@@ -28,14 +29,33 @@ public CameraHostApiImpl(
   @Override
   @NonNull
   public Long getCameraInfo(@NonNull Long identifier) {
-    Camera camera = (Camera) Objects.requireNonNull(instanceManager.getInstance(identifier));
+    Camera camera = getCameraInstance(identifier);
     CameraInfo cameraInfo = camera.getCameraInfo();
 
-    if (!instanceManager.containsInstance(cameraInfo)) {
-      CameraInfoFlutterApiImpl cameraInfoFlutterApiImpl =
-          new CameraInfoFlutterApiImpl(binaryMessenger, instanceManager);
-      cameraInfoFlutterApiImpl.create(cameraInfo, reply -> {});
-    }
+    CameraInfoFlutterApiImpl cameraInfoFlutterApiImpl =
+        new CameraInfoFlutterApiImpl(binaryMessenger, instanceManager);
+    cameraInfoFlutterApiImpl.create(cameraInfo, reply -> {});
     return instanceManager.getIdentifierForStrongReference(cameraInfo);
   }
+
+  /**
+   * Retrieves the {@link CameraControl} instance that provides access to asynchronous operations
+   * like zoom and focus & metering on the {@link Camera} instance with the specified identifier.
+   */
+  @Override
+  @NonNull
+  public Long getCameraControl(@NonNull Long identifier) {
+    Camera camera = getCameraInstance(identifier);
+    CameraControl cameraControl = camera.getCameraControl();
+
+    CameraControlFlutterApiImpl cameraControlFlutterApiImpl =
+        new CameraControlFlutterApiImpl(binaryMessenger, instanceManager);
+    cameraControlFlutterApiImpl.create(cameraControl, reply -> {});
+    return instanceManager.getIdentifierForStrongReference(cameraControl);
+  }
+
+  /** Retrieives the {@link Camera} instance associated with the specified {@code identifier}. */
+  private Camera getCameraInstance(@NonNull Long identifier) {
+    return (Camera) Objects.requireNonNull(instanceManager.getInstance(identifier));
+  }
 }

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

@@ -1136,6 +1136,9 @@ public interface CameraHostApi {
     @NonNull
     Long getCameraInfo(@NonNull Long identifier);
 
+    @NonNull
+    Long getCameraControl(@NonNull Long identifier);
+
     /** The codec used by CameraHostApi. */
     static @NonNull MessageCodec<Object> getCodec() {
       return new StandardMessageCodec();
@@ -1166,6 +1169,31 @@ static void setup(@NonNull BinaryMessenger binaryMessenger, @Nullable CameraHost
           channel.setMessageHandler(null);
         }
       }
+      {
+        BasicMessageChannel<Object> channel =
+            new BasicMessageChannel<>(
+                binaryMessenger, "dev.flutter.pigeon.CameraHostApi.getCameraControl", getCodec());
+        if (api != null) {
+          channel.setMessageHandler(
+              (message, reply) -> {
+                ArrayList<Object> wrapped = new ArrayList<Object>();
+                ArrayList<Object> args = (ArrayList<Object>) message;
+                Number identifierArg = (Number) args.get(0);
+                try {
+                  Long output =
+                      api.getCameraControl(
+                          (identifierArg == null) ? null : identifierArg.longValue());
+                  wrapped.add(0, output);
+                } catch (Throwable exception) {
+                  ArrayList<Object> wrappedError = wrapError(exception);
+                  wrapped = wrappedError;
+                }
+                reply.reply(wrapped);
+              });
+        } else {
+          channel.setMessageHandler(null);
+        }
+      }
     }
   }
   /** Generated class from Pigeon that represents Flutter messages that can be called from Java. */
@@ -3203,4 +3231,82 @@ static void setup(
       }
     }
   }
+  /** Generated interface from Pigeon that represents a handler of messages from Flutter. */
+  public interface CameraControlHostApi {
+
+    void enableTorch(
+        @NonNull Long identifier, @NonNull Boolean torch, @NonNull Result<Void> result);
+
+    /** The codec used by CameraControlHostApi. */
+    static @NonNull MessageCodec<Object> getCodec() {
+      return new StandardMessageCodec();
+    }
+    /**
+     * Sets up an instance of `CameraControlHostApi` to handle messages through the
+     * `binaryMessenger`.
+     */
+    static void setup(
+        @NonNull BinaryMessenger binaryMessenger, @Nullable CameraControlHostApi api) {
+      {
+        BasicMessageChannel<Object> channel =
+            new BasicMessageChannel<>(
+                binaryMessenger, "dev.flutter.pigeon.CameraControlHostApi.enableTorch", getCodec());
+        if (api != null) {
+          channel.setMessageHandler(
+              (message, reply) -> {
+                ArrayList<Object> wrapped = new ArrayList<Object>();
+                ArrayList<Object> args = (ArrayList<Object>) message;
+                Number identifierArg = (Number) args.get(0);
+                Boolean torchArg = (Boolean) args.get(1);
+                Result<Void> resultCallback =
+                    new Result<Void>() {
+                      public void success(Void result) {
+                        wrapped.add(0, null);
+                        reply.reply(wrapped);
+                      }
+
+                      public void error(Throwable error) {
+                        ArrayList<Object> wrappedError = wrapError(error);
+                        reply.reply(wrappedError);
+                      }
+                    };
+
+                api.enableTorch(
+                    (identifierArg == null) ? null : identifierArg.longValue(),
+                    torchArg,
+                    resultCallback);
+              });
+        } else {
+          channel.setMessageHandler(null);
+        }
+      }
+    }
+  }
+  /** Generated class from Pigeon that represents Flutter messages that can be called from Java. */
+  public static class CameraControlFlutterApi {
+    private final @NonNull BinaryMessenger binaryMessenger;
+
+    public CameraControlFlutterApi(@NonNull BinaryMessenger argBinaryMessenger) {
+      this.binaryMessenger = argBinaryMessenger;
+    }
+
+    /** Public interface for sending reply. */
+    @SuppressWarnings("UnknownNullness")
+    public interface Reply<T> {
+      void reply(T reply);
+    }
+    /** The codec used by CameraControlFlutterApi. */
+    static @NonNull MessageCodec<Object> getCodec() {
+      return new StandardMessageCodec();
+    }
+
+    public void create(@NonNull Long identifierArg, @NonNull Reply<Void> callback) {
+      BasicMessageChannel<Object> channel =
+          new BasicMessageChannel<>(
+              binaryMessenger, "dev.flutter.pigeon.CameraControlFlutterApi.create", getCodec());
+      channel.send(
+          new ArrayList<Object>(Collections.singletonList(identifierArg)),
+          channelReply -> callback.reply(null));
+    }
+  }
 }

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

@@ -24,9 +24,12 @@ public class ImageAnalysisHostApiImpl implements ImageAnalysisHostApi {
   @VisibleForTesting @NonNull public CameraXProxy cameraXProxy = new CameraXProxy();
 
   public ImageAnalysisHostApiImpl(
-      @NonNull BinaryMessenger binaryMessenger, @NonNull InstanceManager instanceManager) {
+      @NonNull BinaryMessenger binaryMessenger,
+      @NonNull InstanceManager instanceManager,
+      @NonNull Context context) {
     this.binaryMessenger = binaryMessenger;
     this.instanceManager = instanceManager;
+    this.context = context;
   }
 
   /**