Upstream ResourceManager

ui/android/java/src/org/chromium/ui/resources/ResourceLoader.java

+// Copyright 2014 The Chromium 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 org.chromium.ui.resources;
+
+/**
+ * A class responsible for loading {@link Resource}s for the {@link ResourceManager}.
+ */
+public abstract class ResourceLoader {
+    /**
+     * A callback that specifies when a {@link Resource} has been loaded and can be exposed to the
+     * CC layer.
+     */
+    public interface ResourceLoaderCallback {
+        /**
+         * Called when a resource as finished loading.  Note that it is up to the caller to recycle
+         * any {@link android.graphics.Bitmap}s or clean up any state after making this call.
+         * @param resType  The {@link ResourceType} that loaded the resource.
+         * @param resId    The Android id of the loaded resource.
+         * @param resource The {@link Resource} of the resource, or {@code null} if one could
+         *                 not be loaded.
+         */
+        void onResourceLoaded(int resType, int resId, Resource resource);
+    }
+
+    private final int mResourceType;
+    private final ResourceLoaderCallback mCallback;
+
+    /**
+     * Creates an instance of a {@link ResourceLoader}.
+     * @param resourceType The resource type category this {@link ResourceLoader} is loading.
+     * @param callback     The {@link ResourceLoaderCallback} to notify when a {@link Resource} is
+     *                     loaded.
+     */
+    public ResourceLoader(int resourceType, ResourceLoaderCallback callback) {
+        mResourceType = resourceType;
+        mCallback = callback;
+    }
+
+    /**
+     * @return What resource type this {@link ResourceLoader} is responsible for loading.
+     */
+    public int getResourceType() {
+        return mResourceType;
+    }
+
+    /**
+     * Requests that a resource specified by {@code resId} be loaded from this
+     * {@link ResourceLoader}.  This may or may not actually load the resource and notify the
+     * {@link ResourceLoaderCallback} depending on the internal behavior of the particular loader.
+     * @param resId The id of the {@link Resource} to load.
+     */
+    public abstract void loadResource(int resId);
+
+    /**
+     * Requests that a resource be pre-loaded.  This will typically happen asynchronously.
+     * @param resId The id of the {@link Resource} to load.
+     */
+    public abstract void preloadResource(int resId);
+
+    /**
+     * A helper method for subclasses to notify that the {@link Resource} specified by {@code resId}
+     * is done loading.
+     * @param resId    The id of the {@link Resource} that loaded or failed.
+     * @param resource The {@link Resource}, or {@code null} if the load failed.
+     */
+    protected void notifyLoadFinished(int resId, Resource resource) {
+        if (mCallback != null) mCallback.onResourceLoaded(getResourceType(), resId, resource);
+    }
+}