Develop an application using the User Interface and item/price below to calculate the price of a pizza based on its size and toppings. When the user selects a size and toppings for the pizza and clicks the calculate button, the application should calculate the price of the pizza, add the price of the selected toppings to the base price of the pizza.
The pizza calculator will include Size: small, medium, large; Toppings: sausage, olives, pepperoni, mushrooms, salami, anchovies.