Adds a new TextFormField.

<void> FormFieldCollection.addTextFormField(<Number> emptyWidth, [<RequestTextFormFieldCallback> callback], [<ErrorCallback> errorCallback])


Parameter Description
emptyWidth Specifies the horizontal extension, in twips, of the TextFormField, when there is no text. When this parameter is set to 0, a default value is used.
callback Optional. Receives the added TextFormField.
errorCallback Optional. Is called when the operation failed with an error.