使用JOptionPane进行输入验证

Question

我正在使用JOptionPane框对程序进行输入验证。每次用户输入非双重语句时，我都会尝试在错误消息后重复输入框。我该怎么做？

    try {
        lengthResult = Double.parseDouble(JOptionPane.showInputDialog("What is the length of your garage in square feet?"));
    }
    catch (NumberFormatException e) {
        JOptionPane.showMessageDialog(null, "Please enter a number in digit format.","Inane error",JOptionPane.ERROR_MESSAGE);
    }

Answer 1

如果您想重复此消息框，直到用户输入有效内容，我会这样：

Double lengthResult = null; //Init to null, which is invalid
String title = "Please anter a number";
int initialType = JOptionPane.QUESTION_MESSAGE;
do {
  try {
    lengthResult = Double.parseDouble(
      JOptionPane.showInputDialog(null,
         "What is the length of your garage in square feet?",
         title, initialType));
  } catch (NumberFormatException e) {
    initialType = JOptionPane.ERROR_MESSAGE;
    title = "Error: Please enter a number!";
  }
} while(lengthResult == null); //Iterate as long as no valid input found

请注意，此检查依赖于lengthResult是Double类型的Object，而不是基本类型double。对于原始的双倍，你需要一些额外的标志，因为你不能用这种方式检查lengthResult值。