@Override
        public Uri getUriForFile(File file) {
            String path;
            try {
                path = file.getCanonicalPath();
            } catch (IOException e) {
                throw new IllegalArgumentException("Failed to resolve canonical path for " + file);
            }

            // Find the most-specific root path
            Map.Entry<String, File> mostSpecific = null;
            for (Map.Entry<String, File> root : mRoots.entrySet()) {
                final String rootPath = root.getValue().getPath();
                if (path.startsWith(rootPath) && (mostSpecific == null
                        || rootPath.length() > mostSpecific.getValue().getPath().length())) {
                    mostSpecific = root;
                }
            }

            if (mostSpecific == null) {
                throw new IllegalArgumentException(
                        "Failed to find configured root that contains " + path);
            }

            // Start at first char of path under root
            final String rootPath = mostSpecific.getValue().getPath();
            if (rootPath.endsWith("/")) {
                path = path.substring(rootPath.length());
            } else {
                path = path.substring(rootPath.length() + 1);
            }

            // Encode the tag and path separately
            path = Uri.encode(mostSpecific.getKey()) + '/' + Uri.encode(path, "/");
            return new Uri.Builder().scheme("content")
                    .authority(mAuthority).encodedPath(path).build();
        }
Add a mapping from a name to a filesystem root. The provider only offers
access to files that live under configured roots.
replugin-sample/host/app/src/main/java/com/qihoo360/replugin/sample/host/FileProvider.java