使用 Vaadin UI 进行改造

Question

I am developing a project with Vaadin where he has to make API calls to some services I have created. To make API calls use retrofit. The problem I'm having is that once I get the (asynchronous) response in the onResponse function override I can't change the UI anymore, otherwise I get the error: "Cannot access state in VaadinSession or UI without locking the session."

 service.getUsers().enqueue(new Callback<>() {

            @Override
            public void onResponse(Call<List<User>> call, Response<List<User>> response) {

                if (response.isSuccessful()) {

                    assert response.body() != null;
                    
                    // Receives data correctly
                    System.out.println("Response: " + response.body());

                    // set and add UI element (Error)
                    setUI(response.body());

                } else {

                    System.out.println("TEST > " + response.errorBody());

                }

            }

            @Override
            public void onFailure(Call<List<User>> call, Throwable throwable) {

                System.out.println("onFailure: " + throwable.getMessage());

            }

        });

Answer 1

You have to update the UI in the access() method:

For example:

getUI().ifPresent(ui -> ui.access(() -> { 
   // update the components
}

Please also read the documentation: https://vaadin.com/docs/v14/flow/advanced/tutorial-push-access