Enables prefetching images

Author: fjcaetano

FastImage.js

@@ -1,5 +1,5 @@
 import React, { PropTypes, Component } from 'react'
-import { requireNativeComponent, Image, View } from 'react-native'
+import { requireNativeComponent, Image, NativeModules, View } from 'react-native'
 
 const resolveAssetSource = require('react-native/Libraries/Image/resolveAssetSource')
 
@@ -50,6 +50,15 @@ FastImage.priority = {
   high: 'high',
 }
 
+FastImage.prefetch = function(source) {
+  let urls = source;
+  if (typeof source === 'string') {
+    urls = [source];
+  }
+
+  NativeModules.FastImageView.prefetch(urls);
+}
+
 const FastImageSourcePropType = PropTypes.shape({
   uri: PropTypes.string,
   headers: PropTypes.objectOf(PropTypes.string),

android/src/main/java/com/dylanvann/fastimage/FastImageViewModule.java

@@ -0,0 +1,39 @@
+package com.dylanvann.fastimage;
+
+import android.app.Activity;
+
+import com.bumptech.glide.Glide;
+import com.bumptech.glide.load.engine.DiskCacheStrategy;
+
+import com.facebook.react.bridge.ReadableArray;
+import com.facebook.react.bridge.ReactApplicationContext;
+import com.facebook.react.bridge.ReactContextBaseJavaModule;
+import com.facebook.react.bridge.ReactMethod;
+
+public class FastImageViewModule extends ReactContextBaseJavaModule {
+	public FastImageViewModule(ReactApplicationContext reactContext) {
+    super(reactContext);
+  }
+
+  @Override
+  public String getName() {
+    return "FastImageView";
+  }
+  
+  @ReactMethod
+  public void prefetch(final ReadableArray urls) {
+    final Activity activity = getCurrentActivity();
+    activity.runOnUiThread(new Runnable() {
+      @Override
+      public void run() {
+        for (int i = 0; i < urls.size(); i++) {
+          Glide
+            .with(activity.getApplicationContext())
+            .load(urls.getString(i))
+            .diskCacheStrategy(DiskCacheStrategy.SOURCE)
+            .preload();
+        }
+      }
+    });
+  }
+}

android/src/main/java/com/dylanvann/fastimage/FastImageViewPackage.java

@@ -1,5 +1,7 @@
 package com.dylanvann.fastimage;
 
+import com.dylanvann.fastimage.FastImageViewModule;
+
 import com.facebook.react.ReactPackage;
 import com.facebook.react.bridge.NativeModule;
 import com.facebook.react.bridge.JavaScriptModule;
@@ -10,10 +12,9 @@
 import java.util.List;
 
 public class FastImageViewPackage implements ReactPackage {
-
     @Override
     public List<NativeModule> createNativeModules(ReactApplicationContext reactContext) {
-        return Collections.emptyList();
+        return Collections.<NativeModule>singletonList(new FastImageViewModule(reactContext));
     }
 
     @Override

ios/FastImage/FFFastImageViewManager.m

@@ -1,6 +1,8 @@
 #import "FFFastImageViewManager.h"
 #import "FFFastImageView.h"
 
+#import <SDWebImage/SDWebImagePrefetcher.h>
+
 @implementation FFFastImageViewManager
 
 RCT_EXPORT_MODULE(FastImageView)
@@ -16,5 +18,9 @@ - (FFFastImageView*)view {
 RCT_EXPORT_VIEW_PROPERTY(resizeMode, RCTResizeMode);
 RCT_EXPORT_VIEW_PROPERTY(onFastImageError, RCTDirectEventBlock);
 RCT_EXPORT_VIEW_PROPERTY(onFastImageLoad, RCTDirectEventBlock);
+RCT_EXPORT_METHOD(prefetch:(nonnull NSArray<NSURL *> *)urls)
+{
+    [[SDWebImagePrefetcher sharedImagePrefetcher] prefetchURLs:urls];
+}
 
 @end