BaseBitmapDataSubscriber.java

/*
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

package com.facebook.imagepipeline.datasource;

import javax.annotation.Nullable;

import android.graphics.Bitmap;

import com.facebook.datasource.BaseDataSubscriber;
import com.facebook.datasource.DataSource;
import com.facebook.datasource.DataSubscriber;
import com.facebook.imagepipeline.image.CloseableBitmap;
import com.facebook.imagepipeline.image.CloseableImage;
import com.facebook.common.references.CloseableReference;

/**
 * Implementation of {@link DataSubscriber} for cases where the client wants access to a bitmap.
 *
 * <p>
 * Sample usage:
 * <pre>
 * <code>
 * dataSource.subscribe(
 *   new BaseBitmapDataSubscriber() {
 *     {@literal @}Override
 *     public void onNewResultImpl(@Nullable Bitmap bitmap) {
 *       // Pass bitmap to system, which makes a copy of the bitmap.
 *       updateStatus(bitmap);
 *       // No need to do any cleanup.
 *     }
 *
 *     {@literal @}Override
 *     public void onFailureImpl(DataSource dataSource) {
 *       // No cleanup required here.
 *     }
 *   });
 * </code>
 * </pre>
 */
public abstract class BaseBitmapDataSubscriber extends
    BaseDataSubscriber<CloseableReference<CloseableImage>> {

  @Override
  public void onNewResultImpl(DataSource<CloseableReference<CloseableImage>> dataSource) {
    if (!dataSource.isFinished()) {
      return;
    }

    CloseableReference<CloseableImage> closeableImageRef = dataSource.getResult();
    Bitmap bitmap = null;
    if (closeableImageRef != null &&
        closeableImageRef.get() instanceof CloseableBitmap) {
      bitmap = ((CloseableBitmap) closeableImageRef.get()).getUnderlyingBitmap();
    }

    try {
      onNewResultImpl(bitmap);
    } finally {
      CloseableReference.closeSafely(closeableImageRef);
    }
  }

  /**
   * The bitmap provided to this method is only guaranteed to be around for the lifespan of the
   * method.
   *
   * <p>The framework will free the bitmap's memory after this method has completed.
   * @param bitmap
   */
  protected abstract void onNewResultImpl(@Nullable Bitmap bitmap);
}