片段中CONNECTIVITY_SERVICE的上下文是什么？我也检查了getActivity，但它给出了一个错误。

public boolean isOnline() {
    ConnectivityManager connectionManager = (ConnectivityManager) 
        getSystemService(Context.CONNECTIVITY_SERVICE);
    try {
        if (connectionManager.getActiveNetworkInfo().isConnected()) {
            Log.d("ConStatus", "Data Connection On");
            return true;
        } else {
            Log.d("ConStatus", "Data Connection off");
            return false;
        }
    } catch (NullPointerException e) {
        Log.i("ConStatus", "No Active Connection");
        return false;
    }
}