public BaseImageList(ContentResolver resolver, Uri uri, int sort, String bucketId) {
    mSort = sort;
    mBaseUri = uri;
    mBucketId = bucketId;
    mContentResolver = resolver;
    mCursor = createCursor();

    if (mCursor == null) {
      Log.w(TAG, "createCursor returns null.");
    }

    // TODO: We need to clear the cache because we may "reopen" the image
    // list. After we implement the image list state, we can remove this
    // kind of usage.
    mCache.clear();
  }
 protected void invalidateCache() {
   mCache.clear();
 }