它是 dart 中的 substring() 方法中的错误还是错误或其他什么？。 substring() 工作不正常。 有人可以解释原因吗

Question

I have a textfield, which i am validating in such a way that the entered value should have one '.' (dot or point or decimal). if another '.'(dot or point or decimal) is encountered then we remove that. I have written a function for that which uses substring() method. It works fine when it has only one '.' (dot or point or decimal), and also removes the second
'.' (dot or point or decimal) when encounterd, works fine and as expected. but the problem is that when I enter the '.' (dot or point or decimal) another time or multiple time. the substring() method doesn't work at all. All the logs are printed correctly but substring() mehod is not giving correct logic.

Here is my code.

UI Textfield

Padding(
  padding: EdgeInsets.all(16),
  child: TextField(
    controller: ctrl,
    onChanged: (text) {
      TextFieldType.isNumeric(text, true, ctrl);
    },
  ))

Logical code is kept in a Class called TextFieldType.

class TextFieldType {
  static bool isNumeric(
      String s, bool allowDecimal, TextEditingController controller) {
    if (s == null) return false;
    if (s.isEmpty) return false;

    if (allowDecimal) {
      print("Inside allowDecimal");
      if (s.contains('.')) {
        print("dot is present");
        if ('.'.allMatches(s).length == 1) {
          print("only one dot present");
          return true;
        } else {
          print("Substring of s ->  ${s.substring(0, s.length - 1)}");
          print("length of s -> ${s.length - 1}");
          controller.text = s.substring(0, s.length - 1);
          return false;
        }
      }
      return true;
    }
    return true;
  }
}

As you can clearly see in the gif that after the 12.55 when I entered the '.' (dot or point or decimal)then the substring() worked perfectly. but when I entered the dot again and again then the substring() function doesn't removed that '.' (dot or point or decimal). Why is it behaving like that.

I created the seperate project and tried in that as well but same problem.

Here are logs of the function/method.

I am using almost similar logic which do not allow dot in textfield. only numbers are allowed. it was working good so why this logic is not ??

I request every one to go through this question and have look on it and try to understand and provide a solution which resolves this problem

Thankyou !

Answer 1

From your question, I could think of one Bruteforce though. You could create a boolean variable and initialize it as false. Once you iterate through your string characters if you find a '.' flag that variable as true and change the state of the application. if you find any other in that text, replace it with "". I'm not a 100 percent sure this would work but you could try though. You could declare a condition like

if(thatbool!=true){
// Some Logic
}
else{
//Some Other Logic
}