实现几个连续输入的textfield

如图所示，需要实现连续输入和删除的textfield

代码如下：

首先定义一个宏来实现过滤非法字符串，让输入的字符都是我定义的里面的字符。

#define kInputNumbers  @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789\n"

下面是定义的4个textfield

@property (retain, nonatomic) IBOutlet JDTextField *textField1;
@property (retain, nonatomic) IBOutlet JDTextField *textField2;
@property (retain, nonatomic) IBOutlet JDTextField *textField3;

@property (retain, nonatomic) IBOutlet JDTextField *textField4;

因为并没有直接可以调用的方法，所以要自己加上观察

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textFieldTextDidChange:) name:UITextFieldTextDidChangeNotification object:nil];

/**
 *  为了统一界面，在第一个field之前加上@“ ”
 *
 *  @param textField
 */
- (void) textFieldDidBeginEditing:(UITextField *)textField{
    if (textField == _textField1 && !_isDelete) {
        textField.text = @" ";
    }
}

/**
 *  对应的field改变之前调用这个方法，在这里面来控制从前面格子往后跳转
 *
 *  @param textField textField
 *  @param range     传入的是改变之前光标所在的位置和长度，如果是删除的话是改变后光标的位置，长度为-1
 *  @param string    改变的字符
 *
 *  @return YES的时候确认改变，NO的时候抛弃改变（可以用来过滤字符）
 */
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
    //过滤非法字符
    NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:kInputNumbers] invertedSet];
    NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
    BOOL basicTest = [string isEqualToString:filtered];
    if (!basicTest) {
        return NO;
    }
    //确定是否是删除键
    _isDelete = string.length <= 0 ? YES : NO;
    if (textField == _textField1) {
        //这个方法确保手动点击某个textfield时可以实现跳到下一个
        if (range.location == 5) {
            [textField resignFirstResponder];
            _textField2.enabled = YES;
            [_textField2 becomeFirstResponder];
            textField.enabled = NO;
            return YES;
        }
        if (range.location == 0 && _isDelete)
        {
            return NO;
        }
       
    }
    else if (textField == _textField2) {
        if (range.location == 5) {
            [textField resignFirstResponder];
            _textField3.enabled = YES;
            [_textField3 becomeFirstResponder];
            textField.enabled = NO;
            return YES;
        }
        if (range.location == 0 && _isDelete){
            [textField resignFirstResponder];
            _textField1.enabled = YES;
            [_textField1 becomeFirstResponder];
            textField.enabled = NO;
            return YES;
        }
    }
    else if (textField == _textField3) {
        if (range.location == 5) {
            [textField resignFirstResponder];
            _textField4.enabled = YES;
            [_textField4 becomeFirstResponder];
            textField.enabled = NO;
            return YES;
        }
        if (range.location == 0 && _isDelete){
            [textField resignFirstResponder];
            _textField2.enabled = YES;
            [_textField2 becomeFirstResponder];
            textField.enabled = NO;
            return YES;
        }
    }
    else{
        if (range.location == 0 && _isDelete){
            [textField resignFirstResponder];
            _textField3.enabled = YES;
            [_textField3 becomeFirstResponder];
            textField.enabled = NO;
            return YES;
        }
        return range.location <= 4  ;
    }
    return YES;
}

/**
 *  观察textfield改变之后的属性时调用这个方法，在这个方法里面控制往前面的格子里跳转（因为光标在第一个的时候没有回调方法，所以要在每个之前加上@“ ”）
 *
 *  @param notification 传入观察的对象
 */
- (void)textFieldTextDidChange:(NSNotification *)notification
{
    self.moneyLabel.hidden = YES;
    self.checkLeftBtn.enabled = NO;
    self.saveAndUseBtn.enabled = NO;
    UITextField *textField = (UITextField *)[notification object];
    if (!_isDelete) {
        if (textField == _textField1 ) {
            if (textField.text.length >= 5) {
                _textField2.enabled = YES;
                [textField resignFirstResponder];
                [_textField2 becomeFirstResponder];
                _textField2.text = @" ";
                textField.enabled = NO;
            }
        }else if(textField == _textField2 ){
            if (textField.text.length >= 5) {
                _textField3.enabled = YES;
                [textField resignFirstResponder];
                [_textField3 becomeFirstResponder];
                _textField3.text = @" ";
                textField.enabled = NO;
            }
        }else if (textField == _textField3 ){
            if (textField.text.length >= 5) {
                _textField4.enabled = YES;
                [textField resignFirstResponder];
                [_textField4 becomeFirstResponder];
                _textField4.text = @" ";
                textField.enabled = NO;
            }
        }
    }
    if (_textField1.text.length + _textField2.text.length + _textField3.text.length + _textField4.text.length>= 20) {
        self.checkLeftBtn.enabled = YES;
        self.saveAndUseBtn.enabled = YES;
    }
   

}