Firebase存储URL错误令牌

Question

 try {
                    InputStream is = (InputStream) new URL(storage.getReferenceFromUrl(reference).getDownloadUrl().getResult().toString()).getContent();
                    d = BitmapFactory.decodeStream(is);
                    is.close();
                } catch (Exception e) {
                }

我尝试同时从Firebase存储中下载多个图片。现在我尝试这样做之后将这个方法放在一个循环中，但它一直给我这个错误

E/StorageUtil: error getting token java.util.concurrent.ExecutionException: com.google.android.gms.internal.zzanu: Please sign in before trying to get a token.