[camera] Add Android & iOS implementations for pausing the camera preview

packages/camera/camera/android/build.gradle

@@ -49,7 +49,7 @@ android {
 dependencies {
     compileOnly 'androidx.annotation:annotation:1.1.0'
     testImplementation 'junit:junit:4.12'
-    testImplementation 'org.mockito:mockito-inline:3.5.13'
+    testImplementation 'org.mockito:mockito-inline:3.11.0'
     testImplementation 'androidx.test:core:1.3.0'
     testImplementation 'org.robolectric:robolectric:4.3'
 }

packages/camera/camera/android/src/main/java/io/flutter/plugins/camera/CameraRegionUtils.java

@@ -0,0 +1,138 @@
+// 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.camera;
+
+import android.annotation.TargetApi;
+import android.hardware.camera2.CaptureRequest;
+import android.hardware.camera2.params.MeteringRectangle;
+import android.os.Build;
+import android.util.Size;
+import androidx.annotation.NonNull;
+import androidx.annotation.VisibleForTesting;
+import java.util.Arrays;
+
+/**
+ * Utility class offering functions to calculate values regarding the camera boundaries.
+ *
+ * <p>The functions are used to calculate focus and exposure settings.
+ */
+public final class CameraRegionUtils {
+
+  /**
+   * Obtains the boundaries for the currently active camera, that can be used for calculating
+   * MeteringRectangle instances required for setting focus or exposure settings.
+   *
+   * @param cameraProperties - Collection of the characteristics for the current camera device.
+   * @param requestBuilder - The request builder for the current capture request.
+   * @return The boundaries for the current camera device.
+   */
+  public static Size getCameraBoundaries(
+      @NonNull CameraProperties cameraProperties, @NonNull CaptureRequest.Builder requestBuilder) {
+    // No distortion correction support
+    if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.P
+        && supportsDistortionCorrection(cameraProperties)) {
+      // Get the current distortion correction mode
+      Integer distortionCorrectionMode =
+          requestBuilder.get(CaptureRequest.DISTORTION_CORRECTION_MODE);
+
+      // Return the correct boundaries depending on the mode
+      android.graphics.Rect rect;
+      if (distortionCorrectionMode == null
+          || distortionCorrectionMode == CaptureRequest.DISTORTION_CORRECTION_MODE_OFF) {
+        rect = cameraProperties.getSensorInfoPreCorrectionActiveArraySize();
+      } else {
+        rect = cameraProperties.getSensorInfoActiveArraySize();
+      }
+
+      // Return camera boundaries
+      return rect == null ? null : new Size(rect.width(), rect.height());
+    } else {
+      // Return camera boundaries
+      return cameraProperties.getSensorInfoPixelArraySize();
+    }
+  }
+
+  /**
+   * Converts a point into a {@link MeteringRectangle} with the supplied coordinates as the centre
+   * point.
+   *
+   * <p>Since the Camera API (due to cross-platform constraints) only accepts a point when
+   * configuring a specific focus or exposure area and Android requires a rectangle to configure
+   * these settings there is a need to convert the point into a rectangle. This method will create
+   * the required rectangle with an arbitrarily size that is a 10th of the current viewport and the
+   * coordinates as the centre point.
+   *
+   * @param boundaries - The camera boundaries to calculate the metering rectangle for.
+   * @param x x - 1 >= coordinate >= 0
+   * @param y y - 1 >= coordinate >= 0
+   * @return The dimensions of the metering rectangle based on the supplied coordinates and
+   *     boundaries.
+   */
+  public static MeteringRectangle convertPointToMeteringRectangle(
+      @NonNull Size boundaries, double x, double y) {
+    assert (boundaries.getWidth() > 0 && boundaries.getHeight() > 0);
+    assert (x >= 0 && x <= 1);
+    assert (y >= 0 && y <= 1);
+
+    // Interpolate the target coordinate
+    int targetX = (int) Math.round(x * ((double) (boundaries.getWidth() - 1)));
+    int targetY = (int) Math.round(y * ((double) (boundaries.getHeight() - 1)));
+    // Since the Camera API only allows Determine the dimensions of the metering rectangle (10th of
+    // the viewport)
+    int targetWidth = (int) Math.round(((double) boundaries.getWidth()) / 10d);
+    int targetHeight = (int) Math.round(((double) boundaries.getHeight()) / 10d);
+    // Adjust target coordinate to represent top-left corner of metering rectangle
+    targetX -= targetWidth / 2;
+    targetY -= targetHeight / 2;
+    // Adjust target coordinate as to not fall out of bounds
+    if (targetX < 0) targetX = 0;
+    if (targetY < 0) targetY = 0;
+    int maxTargetX = boundaries.getWidth() - 1 - targetWidth;
+    int maxTargetY = boundaries.getHeight() - 1 - targetHeight;
+    if (targetX > maxTargetX) targetX = maxTargetX;
+    if (targetY > maxTargetY) targetY = maxTargetY;
+
+    // Build the metering rectangle
+    return MeteringRectangleFactory.create(targetX, targetY, targetWidth, targetHeight, 1);
+  }
+
+  @TargetApi(Build.VERSION_CODES.P)
+  private static boolean supportsDistortionCorrection(CameraProperties cameraProperties) {
+    int[] availableDistortionCorrectionModes =
+        cameraProperties.getDistortionCorrectionAvailableModes();
+    if (availableDistortionCorrectionModes == null) {
+      availableDistortionCorrectionModes = new int[0];
+    }
+    long nonOffModesSupported =
+        Arrays.stream(availableDistortionCorrectionModes)
+            .filter((value) -> value != CaptureRequest.DISTORTION_CORRECTION_MODE_OFF)
+            .count();
+    return nonOffModesSupported > 0;
+  }
+
+  /** Factory class that assists in creating a {@link MeteringRectangle} instance. */
+  static class MeteringRectangleFactory {
+    /**
+     * Creates a new instance of the {@link MeteringRectangle} class.
+     *
+     * <p>This method is visible for testing purposes only and should never be used outside this *
+     * class.
+     *
+     * @param x coordinate >= 0
+     * @param y coordinate >= 0
+     * @param width width >= 0
+     * @param height height >= 0
+     * @param meteringWeight weight between {@value MeteringRectangle#METERING_WEIGHT_MIN} and
+     *     {@value MeteringRectangle#METERING_WEIGHT_MAX} inclusively
+     * @return new instance of the {@link MeteringRectangle} class.
+     * @throws IllegalArgumentException if any of the parameters were negative
+     */
+    @VisibleForTesting
+    public static MeteringRectangle create(
+        int x, int y, int width, int height, int meteringWeight) {
+      return new MeteringRectangle(x, y, width, height, meteringWeight);
+    }
+  }
+}

packages/camera/camera/android/src/main/java/io/flutter/plugins/camera/features/exposurepoint/ExposurePointFeature.java

@@ -6,28 +6,36 @@
 
 import android.hardware.camera2.CaptureRequest;
 import android.hardware.camera2.params.MeteringRectangle;
-import android.util.Log;
-import androidx.annotation.NonNull;
+import android.util.Size;
 import io.flutter.plugins.camera.CameraProperties;
+import io.flutter.plugins.camera.CameraRegionUtils;
 import io.flutter.plugins.camera.features.CameraFeature;
 import io.flutter.plugins.camera.features.Point;
-import io.flutter.plugins.camera.types.CameraRegions;
 
 /** Exposure point controls where in the frame exposure metering will come from. */
 public class ExposurePointFeature extends CameraFeature<Point> {
 
-  private final CameraRegions cameraRegions;
-  private Point currentSetting = new Point(0.0, 0.0);
+  private Size cameraBoundaries;
+  private Point exposurePoint;
+  private MeteringRectangle exposureRectangle;
 
   /**
    * Creates a new instance of the {@link ExposurePointFeature}.
    *
    * @param cameraProperties Collection of the characteristics for the current camera device.
-   * @param cameraRegions Utility class to assist in calculating exposure boundaries.
    */
-  public ExposurePointFeature(CameraProperties cameraProperties, CameraRegions cameraRegions) {
+  public ExposurePointFeature(CameraProperties cameraProperties) {
     super(cameraProperties);
-    this.cameraRegions = cameraRegions;
+  }
+
+  /**
+   * Sets the camera boundaries that are required for the exposure point feature to function.
+   *
+   * @param cameraBoundaries - The camera boundaries to set.
+   */
+  public void setCameraBoundaries(Size cameraBoundaries) {
+    this.cameraBoundaries = cameraBoundaries;
+    this.buildExposureRectangle();
   }
 
   @Override
@@ -37,23 +45,19 @@ public String getDebugName() {
 
   @Override
   public Point getValue() {
-    return currentSetting;
+    return exposurePoint;
   }
 
   @Override
-  public void setValue(@NonNull Point value) {
-    this.currentSetting = value;
-
-    if (value.x == null || value.y == null) {
-      cameraRegions.resetAutoExposureMeteringRectangle();
-    } else {
-      cameraRegions.setAutoExposureMeteringRectangleFromPoint(value.x, value.y);
-    }
+  public void setValue(Point value) {
+    this.exposurePoint = value == null || value.x == null || value.y == null ? null : value;
+    this.buildExposureRectangle();
   }
 
   // Whether or not this camera can set the exposure point.
   @Override
   public boolean checkIsSupported() {
+    if (cameraBoundaries == null) return false;
     Integer supportedRegions = cameraProperties.getControlMaxRegionsAutoExposure();
     return supportedRegions != null && supportedRegions > 0;
   }
@@ -63,16 +67,21 @@ public void updateBuilder(CaptureRequest.Builder requestBuilder) {
     if (!checkIsSupported()) {
       return;
     }
-
-    MeteringRectangle aeRect = null;
-    try {
-      aeRect = cameraRegions.getAEMeteringRectangle();
-    } catch (Exception e) {
-      Log.w("Camera", "Unable to retrieve the Auto Exposure metering rectangle.", e);
-    }
-
     requestBuilder.set(
         CaptureRequest.CONTROL_AE_REGIONS,
-        aeRect == null ? null : new MeteringRectangle[] {aeRect});
+        exposureRectangle == null ? null : new MeteringRectangle[] {exposureRectangle});
+  }
+
+  private void buildExposureRectangle() {
+    if (!checkIsSupported()) {
+      return;
+    }
+    if (this.exposurePoint == null) {
+      this.exposureRectangle = null;
+    } else {
+      this.exposureRectangle =
+          CameraRegionUtils.convertPointToMeteringRectangle(
+              this.cameraBoundaries, this.exposurePoint.x, this.exposurePoint.y);
+    }
   }
 }

packages/camera/camera/android/src/main/java/io/flutter/plugins/camera/features/focuspoint/FocusPointFeature.java

@@ -0,0 +1,87 @@
+// Copyright 2019 The Chromium 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.camera.features.focuspoint;
+
+import android.hardware.camera2.CaptureRequest;
+import android.hardware.camera2.params.MeteringRectangle;
+import android.util.Size;
+import io.flutter.plugins.camera.CameraProperties;
+import io.flutter.plugins.camera.CameraRegionUtils;
+import io.flutter.plugins.camera.features.CameraFeature;
+import io.flutter.plugins.camera.features.Point;
+
+/** Focus point controls where in the frame focus will come from. */
+public class FocusPointFeature extends CameraFeature<Point> {
+
+  private Size cameraBoundaries;
+  private Point focusPoint;
+  private MeteringRectangle focusRectangle;
+
+  /**
+   * Creates a new instance of the {@link FocusPointFeature}.
+   *
+   * @param cameraProperties Collection of the characteristics for the current camera device.
+   */
+  public FocusPointFeature(CameraProperties cameraProperties) {
+    super(cameraProperties);
+  }
+
+  /**
+   * Sets the camera boundaries that are required for the focus point feature to function.
+   *
+   * @param cameraBoundaries - The camera boundaries to set.
+   */
+  public void setCameraBoundaries(Size cameraBoundaries) {
+    this.cameraBoundaries = cameraBoundaries;
+    this.buildFocusRectangle();
+  }
+
+  @Override
+  public String getDebugName() {
+    return "FocusPointFeature";
+  }
+
+  @Override
+  public Point getValue() {
+    return focusPoint;
+  }
+
+  @Override
+  public void setValue(Point value) {
+    this.focusPoint = value == null || value.x == null || value.y == null ? null : value;
+    this.buildFocusRectangle();
+  }
+
+  // Whether or not this camera can set the exposure point.
+  @Override
+  public boolean checkIsSupported() {
+    if (cameraBoundaries == null) return false;
+    Integer supportedRegions = cameraProperties.getControlMaxRegionsAutoFocus();
+    return supportedRegions != null && supportedRegions > 0;
+  }
+
+  @Override
+  public void updateBuilder(CaptureRequest.Builder requestBuilder) {
+    if (!checkIsSupported()) {
+      return;
+    }
+    requestBuilder.set(
+        CaptureRequest.CONTROL_AF_REGIONS,
+        focusRectangle == null ? null : new MeteringRectangle[] {focusRectangle});
+  }
+
+  private void buildFocusRectangle() {
+    if (!checkIsSupported()) {
+      return;
+    }
+    if (this.focusPoint == null) {
+      this.focusRectangle = null;
+    } else {
+      this.focusRectangle =
+          CameraRegionUtils.convertPointToMeteringRectangle(
+              this.cameraBoundaries, this.focusPoint.x, this.focusPoint.y);
+    }
+  }
+}