com.facebook.react.views.imagehelper.MultiSourceHelper Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of react-native Show documentation
Show all versions of react-native Show documentation
A framework for building native apps with React
/**
* 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.react.views.imagehelper;
import javax.annotation.Nullable;
import java.util.List;
import com.facebook.imagepipeline.core.ImagePipeline;
import com.facebook.imagepipeline.core.ImagePipelineFactory;
import com.facebook.react.views.imagehelper.ImageSource;
/**
* Helper class for dealing with multisource images.
*/
public class MultiSourceHelper {
public static class MultiSourceResult {
private final @Nullable ImageSource bestResult;
private final @Nullable ImageSource bestResultInCache;
private MultiSourceResult(
@Nullable ImageSource bestResult,
@Nullable ImageSource bestResultInCache) {
this.bestResult = bestResult;
this.bestResultInCache = bestResultInCache;
}
/**
* Get the best result overall (closest in size to the view's size). Can be null if there were
* no sources to choose from, or if there were more than 1 sources but width/height were 0.
*/
public @Nullable ImageSource getBestResult() {
return bestResult;
}
/**
* Get the best result (closest in size to the view's size) that is also in cache. If this would
* be the same as the source from {@link #getBestResult()}, this will return {@code null}
* instead.
*/
public @Nullable ImageSource getBestResultInCache() {
return bestResultInCache;
}
}
public static MultiSourceResult getBestSourceForSize(
int width,
int height,
List sources) {
return getBestSourceForSize(width, height, sources, 1.0d);
}
/**
* Chooses the image source with the size closest to the target image size.
*
* @param width the width of the view that will be used to display this image
* @param height the height of the view that will be used to display this image
* @param sources the list of potential image sources to choose from
* @param multiplier the area of the view will be multiplied by this number before calculating the
* best source; this is useful if the image will be displayed bigger than the view
* (e.g. zoomed)
*/
public static MultiSourceResult getBestSourceForSize(
int width,
int height,
List sources,
double multiplier) {
// no sources
if (sources.isEmpty()) {
return new MultiSourceResult(null, null);
}
// single source
if (sources.size() == 1) {
return new MultiSourceResult(sources.get(0), null);
}
// For multiple sources, we first need the view's size in order to determine the best source to
// load. If we haven't been measured yet, return null and wait for onSizeChanged.
if (width <= 0 || height <= 0) {
return new MultiSourceResult(null, null);
}
ImagePipeline imagePipeline = ImagePipelineFactory.getInstance().getImagePipeline();
ImageSource best = null;
ImageSource bestCached = null;
final double viewArea = width * height * multiplier;
double bestPrecision = Double.MAX_VALUE;
double bestCachePrecision = Double.MAX_VALUE;
for (ImageSource source : sources) {
double precision = Math.abs(1.0 - source.getSize() / viewArea);
if (precision < bestPrecision) {
bestPrecision = precision;
best = source;
}
if (precision < bestCachePrecision &&
(imagePipeline.isInBitmapMemoryCache(source.getUri()) ||
imagePipeline.isInDiskCacheSync(source.getUri()))) {
bestCachePrecision = precision;
bestCached = source;
}
}
if (bestCached != null && best != null && bestCached.getSource().equals(best.getSource())) {
bestCached = null;
}
return new MultiSourceResult(best, bestCached);
}
}