public void addRoot(String name, File root) {
            if (TextUtils.isEmpty(name)) {
                throw new IllegalArgumentException("Name must not be empty");
            }

            try {
                // Resolve to canonical path to keep path checking fast
                root = root.getCanonicalFile();
            } catch (IOException e) {
                throw new IllegalArgumentException(
                        "Failed to resolve canonical path for " + root, e);
            }

            mRoots.put(name, root);
        }
Add a mapping from a name to a filesystem root. The provider only offers
access to files that live under configured roots.
replugin-sample/plugin/plugin-demo1/app/src/main/java/com/qihoo360/replugin/sample/demo1/provider/FileProvider.java