[camerax] Retrieve exposure and zoom camera information (flutter#3798)

Implements retrieval of exposure and zoom camera information. Specifically, implements the following:

- `getMinExposureOffset()`
- `getMaxExposureOffset()`
- `getExposureOffsetStepSize()`
- `getMaxZoomLevel()`
- `getMinZoomLevel()`

Part of flutter/flutter#115846.
Part of flutter/flutter#125371.
Part of flutter/flutter#120468.

Author: camsim99

packages/camera/camera_android_camerax/CHANGELOG.md

@@ -20,3 +20,4 @@
 * Updates internal Java InstanceManager to only stop finalization callbacks when stopped.
 * Implements image streaming.
 * Provides LifecycleOwner implementation for Activities that use the plugin that do not implement it themselves.
+* Implements retrieval of camera information.

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

@@ -48,8 +48,10 @@ public void setUp(
     // Set up Host APIs.
     GeneratedCameraXLibrary.InstanceManagerHostApi.setup(
         binaryMessenger, () -> instanceManager.clear());
+    GeneratedCameraXLibrary.CameraHostApi.setup(
+        binaryMessenger, new CameraHostApiImpl(binaryMessenger, instanceManager));
     GeneratedCameraXLibrary.CameraInfoHostApi.setup(
-        binaryMessenger, new CameraInfoHostApiImpl(instanceManager));
+        binaryMessenger, new CameraInfoHostApiImpl(binaryMessenger, instanceManager));
     GeneratedCameraXLibrary.CameraSelectorHostApi.setup(
         binaryMessenger, new CameraSelectorHostApiImpl(binaryMessenger, instanceManager));
     GeneratedCameraXLibrary.JavaObjectHostApi.setup(

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

@@ -0,0 +1,40 @@
+// 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.Camera;
+import androidx.camera.core.CameraInfo;
+import io.flutter.plugin.common.BinaryMessenger;
+import io.flutter.plugins.camerax.GeneratedCameraXLibrary.CameraHostApi;
+import java.util.Objects;
+
+public class CameraHostApiImpl implements CameraHostApi {
+  private final BinaryMessenger binaryMessenger;
+  private final InstanceManager instanceManager;
+
+  public CameraHostApiImpl(
+      @NonNull BinaryMessenger binaryMessenger, @NonNull InstanceManager instanceManager) {
+    this.binaryMessenger = binaryMessenger;
+    this.instanceManager = instanceManager;
+  }
+
+  /**
+   * Retrieves the {@link CameraInfo} instance that contains information about the {@link Camera}
+   * instance with the specified identifier.
+   */
+  @Override
+  @NonNull
+  public Long getCameraInfo(@NonNull Long identifier) {
+    Camera camera = (Camera) Objects.requireNonNull(instanceManager.getInstance(identifier));
+    CameraInfo cameraInfo = camera.getCameraInfo();
+
+    CameraInfoFlutterApiImpl cameraInfoFlutterApiImpl =
+        new CameraInfoFlutterApiImpl(binaryMessenger, instanceManager);
+    cameraInfoFlutterApiImpl.create(cameraInfo, reply -> {});
+
+    return instanceManager.getIdentifierForStrongReference(cameraInfo);
+  }
+}

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

@@ -18,6 +18,8 @@ public CameraInfoFlutterApiImpl(
   }
 
   void create(CameraInfo cameraInfo, Reply<Void> reply) {
-    create(instanceManager.addHostCreatedInstance(cameraInfo), reply);
+    if (!instanceManager.containsInstance(cameraInfo)) {
+      create(instanceManager.addHostCreatedInstance(cameraInfo), reply);
+    }
   }
 }

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

@@ -6,20 +6,64 @@
 
 import androidx.annotation.NonNull;
 import androidx.camera.core.CameraInfo;
+import androidx.camera.core.ExposureState;
+import androidx.camera.core.ZoomState;
+import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugins.camerax.GeneratedCameraXLibrary.CameraInfoHostApi;
 import java.util.Objects;
 
 public class CameraInfoHostApiImpl implements CameraInfoHostApi {
+  private final BinaryMessenger binaryMessenger;
   private final InstanceManager instanceManager;
 
-  public CameraInfoHostApiImpl(InstanceManager instanceManager) {
+  public CameraInfoHostApiImpl(
+      @NonNull BinaryMessenger binaryMessenger, @NonNull InstanceManager instanceManager) {
+    this.binaryMessenger = binaryMessenger;
     this.instanceManager = instanceManager;
   }
 
+  /** Retrieves the sensor rotation in degrees, relative to the device's default orientation. */
   @Override
+  @NonNull
   public Long getSensorRotationDegrees(@NonNull Long identifier) {
     CameraInfo cameraInfo =
         (CameraInfo) Objects.requireNonNull(instanceManager.getInstance(identifier));
     return Long.valueOf(cameraInfo.getSensorRotationDegrees());
   }
+
+  /**
+   * Retrieves the {@link ExposureState} of the {@link CameraInfo} with the specified identifier.
+   */
+  @Override
+  @NonNull
+  public Long getExposureState(@NonNull Long identifier) {
+    CameraInfo cameraInfo =
+        (CameraInfo) Objects.requireNonNull(instanceManager.getInstance(identifier));
+    ExposureState exposureState = cameraInfo.getExposureState();
+
+    ExposureStateFlutterApiImpl exposureStateFlutterApiImpl =
+        new ExposureStateFlutterApiImpl(binaryMessenger, instanceManager);
+    exposureStateFlutterApiImpl.create(exposureState, result -> {});
+
+    return instanceManager.getIdentifierForStrongReference(exposureState);
+  }
+
+  /**
+   * Retrieves the current {@link ZoomState} value of the {@link CameraInfo} with the specified
+   * identifier.
+   */
+  @NonNull
+  @Override
+  public Long getZoomState(@NonNull Long identifier) {
+    CameraInfo cameraInfo =
+        (CameraInfo) Objects.requireNonNull(instanceManager.getInstance(identifier));
+    // TODO(camsim99): Create/return LiveData<ZoomState> once https://github.com/flutter/packages/pull/3419 lands.
+    ZoomState zoomState = cameraInfo.getZoomState().getValue();
+
+    ZoomStateFlutterApiImpl zoomStateFlutterApiImpl =
+        new ZoomStateFlutterApiImpl(binaryMessenger, instanceManager);
+    zoomStateFlutterApiImpl.create(zoomState, result -> {});
+
+    return instanceManager.getIdentifierForStrongReference(zoomState);
+  }
 }

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

@@ -0,0 +1,49 @@
+// 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.util.Range;
+import androidx.annotation.NonNull;
+import androidx.camera.core.ExposureState;
+import io.flutter.plugin.common.BinaryMessenger;
+import io.flutter.plugins.camerax.GeneratedCameraXLibrary.ExposureCompensationRange;
+import io.flutter.plugins.camerax.GeneratedCameraXLibrary.ExposureStateFlutterApi;
+
+public class ExposureStateFlutterApiImpl extends ExposureStateFlutterApi {
+  private final InstanceManager instanceManager;
+
+  public ExposureStateFlutterApiImpl(
+      @NonNull BinaryMessenger binaryMessenger, @NonNull InstanceManager instanceManager) {
+    super(binaryMessenger);
+    this.instanceManager = instanceManager;
+  }
+
+  /**
+   * Creates a {@link ExposureState} on the Dart side with its exposure compensation range that can
+   * be used to set the exposure compensation index and its exposure compensation step, the smallest
+   * step by which the exposure compensation can be changed.
+   */
+  void create(@NonNull ExposureState exposureState, @NonNull Reply<Void> reply) {
+    if (instanceManager.containsInstance(exposureState)) {
+      return;
+    }
+
+    final Range<Integer> exposureCompensationRangeFromState =
+        exposureState.getExposureCompensationRange();
+    ExposureCompensationRange exposureCompensationRange =
+        new ExposureCompensationRange.Builder()
+            .setMinCompensation(exposureCompensationRangeFromState.getLower().longValue())
+            .setMaxCompensation(exposureCompensationRangeFromState.getUpper().longValue())
+            .build();
+    final Double exposureCompensationStep =
+        exposureState.getExposureCompensationStep().doubleValue();
+
+    create(
+        instanceManager.addHostCreatedInstance(exposureState),
+        exposureCompensationRange,
+        exposureCompensationStep,
+        reply);
+  }
+}