说明：  函数插值计算 分别输入已知节点的x,y值，待计算的节点的x值，以及显示结果的文本框。利用文本框和按钮上的事件触发一系列处理方法，包括把文本框里的字符串解析成double类型存放在数组中，以及利用lagrange插值公式计算出结果并填写在结果文本框中。
(Function interpolation calculated separately known input node x, y values to be calculated node x value, and display the results of the text box. The use of text boxes and buttons on the case triggered a series of treatment methods, including text box put the string into a double type of analysis stored in the array, and the use of lagrange interpolation formula to calculate the results and fill in the results text box.)