编写一个简单的计算器程序，实现两个数相加。运行结果如图所示。

在文本框输入两个实数，点击“相加”按钮实现两个实数相加，并在标签中显示相加结果，点击“清除”完成对文本框和运行结果的清除。

-Write a simple calculator program to add two numbers. Run results shown in Fig. Enter two real numbers in the text box and click the " add"　button sum of two real numbers and display the result of the addition on the label, click the " Clear"　text box and the results of running the Clear.