Flutter：Textformfield 验证器不工作

Question

我在 flutter 中使用 TextFormField。我想验证 TextFormField 值应该小于 100 或者它应该是字符 'a' 单独

我试过了

validator: (value) {
                  if (value.length == 0  ) {
                    return ('value is required!');
                  }
                  else if(value != "a"  || value != "A" || int.parse(value) < 0.0 || int.parse(value) > 100  )
                    {
                      return ('value should between 0 to 100 if absent put "A"!');
                    }
                },

但不是working.Anyone请帮帮我。提前致谢

此致，萨西什

Answer 1

当验证器不应显示错误时，请记住 return null。

    if (value.isEmpty) return 'value is required';
    if (value.toLowerCase() == 'a') return null;

    var intValue = int.tryParse(value);
    if (intValue == null) { // not a number
      return 'value should be between 0-100 if absent put A';
    } else {
      return intValue > 100 ? 'value should be between 0-100' : null;
    }

Flutter：Textformfield 验证器不工作

Flutter: Textformfield validator not working

textfield

flutter