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

// 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.graphics.SurfaceTexture;
import android.util.Size;
import android.view.Surface;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.VisibleForTesting;
import androidx.camera.core.Preview;
import androidx.camera.core.SurfaceRequest;
import io.flutter.plugin.common.BinaryMessenger;
import io.flutter.plugins.camerax.GeneratedCameraXLibrary.PreviewHostApi;
import io.flutter.view.TextureRegistry;
import java.util.Objects;
import java.util.concurrent.Executors;

public class PreviewHostApiImpl implements PreviewHostApi {
  private final BinaryMessenger binaryMessenger;
  private final InstanceManager instanceManager;
  private final TextureRegistry textureRegistry;

  @VisibleForTesting public CameraXProxy cameraXProxy = new CameraXProxy();
  @VisibleForTesting public TextureRegistry.SurfaceTextureEntry flutterSurfaceTexture;

  public PreviewHostApiImpl(
      @NonNull BinaryMessenger binaryMessenger,
      @NonNull InstanceManager instanceManager,
      @NonNull TextureRegistry textureRegistry) {
    this.binaryMessenger = binaryMessenger;
    this.instanceManager = instanceManager;
    this.textureRegistry = textureRegistry;
  }

  /** Creates a {@link Preview} with the target rotation and resolution if specified. */
  @Override
  public void create(
      @NonNull Long identifier,
      @Nullable Long rotation,
      @Nullable GeneratedCameraXLibrary.ResolutionInfo targetResolution) {
    Preview.Builder previewBuilder = cameraXProxy.createPreviewBuilder();
    if (rotation != null) {
      previewBuilder.setTargetRotation(rotation.intValue());
    }
    if (targetResolution != null) {
      previewBuilder.setTargetResolution(
          new Size(
              targetResolution.getWidth().intValue(), targetResolution.getHeight().intValue()));
    }
    Preview preview = previewBuilder.build();
    instanceManager.addDartCreatedInstance(preview, identifier);
  }

  /**
   * Sets the {@link Preview.SurfaceProvider} that will be used to provide a {@code Surface} backed
   * by a Flutter {@link TextureRegistry.SurfaceTextureEntry} used to build the {@link Preview}.
   */
  @Override
  public Long setSurfaceProvider(@NonNull Long identifier) {
    Preview preview = (Preview) Objects.requireNonNull(instanceManager.getInstance(identifier));
    flutterSurfaceTexture = textureRegistry.createSurfaceTexture();
    SurfaceTexture surfaceTexture = flutterSurfaceTexture.surfaceTexture();
    Preview.SurfaceProvider surfaceProvider = createSurfaceProvider(surfaceTexture);
    preview.setSurfaceProvider(surfaceProvider);

    return flutterSurfaceTexture.id();
  }

  /**
   * Creates a {@link Preview.SurfaceProvider} that specifies how to provide a {@link Surface} to a
   * {@code Preview} that is backed by a Flutter {@link TextureRegistry.SurfaceTextureEntry}.
   */
  @VisibleForTesting
  public Preview.SurfaceProvider createSurfaceProvider(@NonNull SurfaceTexture surfaceTexture) {
    return new Preview.SurfaceProvider() {
      @Override
      public void onSurfaceRequested(SurfaceRequest request) {
        surfaceTexture.setDefaultBufferSize(
            request.getResolution().getWidth(), request.getResolution().getHeight());
        Surface flutterSurface = cameraXProxy.createSurface(surfaceTexture);
        request.provideSurface(
            flutterSurface,
            Executors.newSingleThreadExecutor(),
            (result) -> {
              // See https://developer.android.com/reference/androidx/camera/core/SurfaceRequest.Result for documentation.
              // Always attempt a release.
              flutterSurface.release();
              int resultCode = result.getResultCode();
              switch (resultCode) {
                case SurfaceRequest.Result.RESULT_REQUEST_CANCELLED:
                case SurfaceRequest.Result.RESULT_WILL_NOT_PROVIDE_SURFACE:
                case SurfaceRequest.Result.RESULT_SURFACE_ALREADY_PROVIDED:
                case SurfaceRequest.Result.RESULT_SURFACE_USED_SUCCESSFULLY:
                  // Only need to release, do nothing.
                  break;
                case SurfaceRequest.Result.RESULT_INVALID_SURFACE: // Intentional fall through.
                default:
                  // Release and send error.
                  SystemServicesFlutterApiImpl systemServicesFlutterApi =
                      cameraXProxy.createSystemServicesFlutterApiImpl(binaryMessenger);
                  systemServicesFlutterApi.sendCameraError(
                      getProvideSurfaceErrorDescription(resultCode), reply -> {});
                  break;
              }
            });
      };
    };
  }

  /**
   * Returns an error description for each {@link SurfaceRequest.Result} that represents an error
   * with providing a surface.
   */
  private String getProvideSurfaceErrorDescription(@Nullable int resultCode) {
    switch (resultCode) {
      case SurfaceRequest.Result.RESULT_INVALID_SURFACE:
        return resultCode + ": Provided surface could not be used by the camera.";
      default:
        return resultCode + ": Attempt to provide a surface resulted with unrecognizable code.";
    }
  }

  /**
   * Releases the Flutter {@link TextureRegistry.SurfaceTextureEntry} if used to provide a surface
   * for a {@link Preview}.
   */
  @Override
  public void releaseFlutterSurfaceTexture() {
    if (flutterSurfaceTexture != null) {
      flutterSurfaceTexture.release();
    }
  }

  /** Returns the resolution information for the specified {@link Preview}. */
  @Override
  public GeneratedCameraXLibrary.ResolutionInfo getResolutionInfo(@NonNull Long identifier) {
    Preview preview = (Preview) Objects.requireNonNull(instanceManager.getInstance(identifier));
    Size resolution = preview.getResolutionInfo().getResolution();

    GeneratedCameraXLibrary.ResolutionInfo.Builder resolutionInfo =
        new GeneratedCameraXLibrary.ResolutionInfo.Builder()
            .setWidth(Long.valueOf(resolution.getWidth()))
            .setHeight(Long.valueOf(resolution.getHeight()));
    return resolutionInfo.build();
  }
}