ValuesManager upload file error

[heavenite]

code:
VLayout vLayout = new VLayout();
final ValuesManager vm = new ValuesManager();
vm.setDataSource(DataSource.get("formTestDMI"));
final DynamicForm form7;
{

form7 = new DynamicForm();
form7.setValuesManager(vm);

HiddenItem id = new HiddenItem("id");
UploadItem item1 = new UploadItem("uploadFile","upload");

form7.setFields(id,item1);

}
IButton submit = new IButton("submit");
submit.addClickHandler(new ClickHandler() {

@Override
public void onClick(ClickEvent event) {
// TODO Auto-generated method stub
vm.saveData();
}
});

vLayout.addMember(form7);
vLayout.addMember(submit);
vLayout.draw();

error:
17:11:33.777 [ERROR] [gwtdemo] 17:11:33.786:WARN:ValuesManager:isc_ValuesManager_0:addMember(): new member form [DynamicForm ID:isc_DynamicForm_0] is flagged as using multipart encoding. Multipart forms require direct form submission to transfer uploaded files to the server - any uploaded files from this member form will be dropped when saving values from this ValuesManager to the server.

[Isomorphic]

Yes, a ValuesManager involves multiple forms so it cannot submit normally.