简单的计算器，界面是基于流布局的界面，适合初学者学习之用，如果发现bug，希望能够私信我，将它完善，给新人一个完美点的程序-Simple calculator interface is based on the flow layout interface, suitable for beginners to learn, If you found a bug, I want to be able to private letter, it would be perfect, a perfect