Add a way to prefetch remote images to cache with Image.prefetch

Summary:Adds `Image.prefetch` to prefetch remote images before they are used in an actual `Image` component. This is based off of #4420 by sospartan and skevy's work.
Closes https://github.com/facebook/react-native/pull/6774

Differential Revision: D3153729

Pulled By: bestander

fb-gh-sync-id: ef61412e051a49b42ae885edce7905a8ca0da23f
fbshipit-source-id: ef61412e051a49b42ae885edce7905a8ca0da23f

ReactAndroid/src/main/java/com/facebook/react/modules/image/BUCK

@@ -0,0 +1,23 @@
+include_defs('//ReactAndroid/DEFS')
+
+android_library(
+  name = 'image',
+  srcs = glob(['*.java']),
+  deps = [
+    react_native_dep('libraries/fresco/fresco-react-native:fbcore'),
+    react_native_dep('libraries/fresco/fresco-react-native:fresco-drawee'),
+    react_native_dep('libraries/fresco/fresco-react-native:fresco-react-native'),
+    react_native_dep('libraries/fresco/fresco-react-native:imagepipeline'),
+    react_native_dep('third-party/java/infer-annotations:infer-annotations'),
+    react_native_dep('third-party/java/jsr-305:jsr-305'),
+    react_native_target('java/com/facebook/react/bridge:bridge'),
+    react_native_target('java/com/facebook/react/common:common'),
+  ],
+  visibility = [
+    'PUBLIC',
+  ],
+)
+
+project_config(
+  src_target = ':image',
+)

ReactAndroid/src/main/java/com/facebook/react/modules/image/ImageLoaderModule.java

@@ -0,0 +1,82 @@
+/**
+ * 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.modules.image;
+
+import android.net.Uri;
+
+import com.facebook.common.executors.CallerThreadExecutor;
+import com.facebook.datasource.BaseDataSubscriber;
+import com.facebook.datasource.DataSource;
+import com.facebook.datasource.DataSubscriber;
+import com.facebook.drawee.backends.pipeline.Fresco;
+import com.facebook.imagepipeline.request.ImageRequest;
+import com.facebook.imagepipeline.request.ImageRequestBuilder;
+import com.facebook.react.bridge.Promise;
+import com.facebook.react.bridge.ReactApplicationContext;
+import com.facebook.react.bridge.ReactContextBaseJavaModule;
+import com.facebook.react.bridge.ReactMethod;
+
+public class ImageLoaderModule extends ReactContextBaseJavaModule {
+
+  private static final String ERROR_INVALID_URI = "E_INVALID_URI";
+  private static final String ERROR_PREFETCH_FAILURE = "E_PREFETCH_FAILURE";
+
+  public ImageLoaderModule(ReactApplicationContext reactContext) {
+    super(reactContext);
+  }
+
+  @Override
+  public String getName() {
+    return "ImageLoader";
+  }
+
+  /**
+   * Prefetches the given image to the Fresco image disk cache.
+   *
+   * @param uriString the URI of the remote image to prefetch
+   * @param promise the promise that is fulfilled when the image is successfully prefetched
+   *                or rejected when there is an error
+   */
+  @ReactMethod
+  public void prefetchImage(String uriString, final Promise promise) {
+    if (uriString == null || uriString.isEmpty()) {
+      promise.reject(ERROR_INVALID_URI, "Cannot prefetch an image for an empty URI");
+      return;
+    }
+
+    Uri uri = Uri.parse(uriString);
+    ImageRequest request = ImageRequestBuilder.newBuilderWithSource(uri).build();
+
+    DataSource<Void> prefetchSource = Fresco.getImagePipeline().prefetchToDiskCache(request, this);
+    DataSubscriber<Void> prefetchSubscriber = new BaseDataSubscriber<Void>() {
+      @Override
+      protected void onNewResultImpl(DataSource<Void> dataSource) {
+        if (!dataSource.isFinished()) {
+          return;
+        }
+        try {
+          promise.resolve(true);
+        } finally {
+          dataSource.close();
+        }
+      }
+
+      @Override
+      protected void onFailureImpl(DataSource<Void> dataSource) {
+        try {
+          promise.reject(ERROR_PREFETCH_FAILURE, dataSource.getFailureCause());
+        } finally {
+          dataSource.close();
+        }
+      }
+    };
+    prefetchSource.subscribe(prefetchSubscriber, CallerThreadExecutor.getInstance());
+  }
+}