- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string;
{ 
 //string就是此時(shí)輸入的那個(gè)字符textField就是此時(shí)正在輸入的那個(gè)輸入框返回YES就是可以改變輸入框的值NO相反
    NSString * toBeString = [textField.text     stringByReplacingCharactersInRange:range withString:string]; 
    // 判斷是否輸入內(nèi)容，或者用戶點(diǎn)擊的是鍵盤的刪除按鈕
    if (![string isEqualToString:@""]) {
        if ([textField isEqual:self.textField]) {
            // 小數(shù)點(diǎn)在字符串中的位置 第一個(gè)數(shù)字從0位置開始
            NSInteger dotLocation = [textField.text rangeOfString:@"."].location;
            if (dotLocation == NSNotFound && range.location != 0) {
                //沒有小數(shù)點(diǎn),最大數(shù)值
                if (range.location >= 9){
                    NSLog(@"單筆金額不能超過億位");
                    if ([string isEqualToString:@"."] && range.location == 9) {
                        return YES;
                    }
                    return NO;
                }
            }
            //判斷輸入多個(gè)小數(shù)點(diǎn),禁止輸入多個(gè)小數(shù)點(diǎn)
            if (dotLocation != NSNotFound){
                if ([string isEqualToString:@"."])return NO;
            }
            //判斷小數(shù)點(diǎn)后最多兩位
            if (dotLocation != NSNotFound && range.location > dotLocation + 2) { return NO; }
            //判斷總長(zhǎng)度
            if (textField.text.length > 11) {
                return NO;
            }
        }
    }
    return YES;
}