How to avoid freezing the UI on heavy computation

Question

Trying to decrypt JSON from server with Interceptor (from dio). But UI freezes during decryption.

class DecryptInterceptor extends Interceptor {

  @override
  Future onResponse(Response response) async {
    response.data = decrypt(response.data); //freezes here
    return super.onResponse(response);
  }

}

Object decrypt(Object object){
  // computations
}

Answer 1

You can use compute property that flutter provides to perform tasks in another isolate. It exists exactly for such tasks.

class DecryptInterceptor extends Interceptor {
  @override
  Future onResponse(Response response) async {
    response.data =await compute(decrypt,response.data); //freezes here
    return super.onResponse(response);
  }
}
  Object decrypt(Object object){
    return result;
  }

It has some restrictions though for the type of data you can pass in argument and retrieve as result. You can learn more here.