UITextField的代理方法中添加类似如下代码

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

{

NSMutableString * futureString = [NSMutableString stringWithString:textField.text];

[futureString  insertString:string atIndex:range.location];

NSInteger flag=0;

const NSInteger limited = 1;

for (int i = futureString.length-1; i>=0; i--) {

if ([futureString characterAtIndex:i] == '.') {

if (flag > limited) {

return NO;

}

break;

}

flag++;

}

return YES;

}