##一.效果图：

实现思路：
1.输入显示试图和系统键盘的出现和隐藏。
2.用UILabel和UITextField实现输入框。
##二.关键代码：

//试图的出现和隐藏方法
- (void)showPayPopView
{
    __weak typeof(self) weakSelf = self;
    [UIView animateWithDuration:AnimationTimeInterval animations:^{
        __strong typeof(weakSelf) strongSelf = weakSelf;
        strongSelf.superView.backgroundColor = [UIColor colorWithWhite:0.3 alpha:0.3];
    } completion:nil];
}

- (void)hidePayPopView
{
    __weak typeof(self) weakSelf = self;
    [UIView animateWithDuration:AnimationTimeInterval animations:^{
        __strong typeof(weakSelf) strongSelf = weakSelf;
        strongSelf.superView.alpha = 0.0;
        strongSelf.frame = CGRectMake(strongSelf.frame.origin.x, kScreenWidth, strongSelf.frame.size.width, strongSelf.frame.size.height);
    } completion:^(BOOL finished) {
        __strong typeof(weakSelf) strongSelf = weakSelf;
        [strongSelf.superView removeFromSuperview];
        strongSelf.superView = nil;
    }];
}

//输入密码或删除时

- (void)updateLabelBoxWithText:(NSString *)text
{
    //输入时
    if (text.length > self.currentText.length) {
        for (int i = 0; i < PasswordBoxNumber; i++)
        {
            UILabel *label = self.labelBoxArray[i];
            if (i < text.length - 1)
            {
                //特殊字符不居中显示，设置文本向下偏移
                NSAttributedString * att1 = [[NSAttributedString alloc] initWithString:@"*" attributes:@{NSBaselineOffsetAttributeName:@(-3)}];
                label.attributedText = att1;
            }
            else if (i == text.length - 1)
            {
                label.text = [text substringWithRange:NSMakeRange(i, 1)];
                [self animationShowTextInLabel: label];
            }
            else
            {
                label.text = @"";
            }
        }
    }
    //删除时
    else
    {
        for (int i = 0; i < PasswordBoxNumber; i++)
        {
            UILabel *label = self.labelBoxArray[i];
            if (i < text.length)
            {
                //特殊字符不居中显示，设置文本向下偏移
                NSAttributedString * att1 = [[NSAttributedString alloc] initWithString:@"*" attributes:@{NSBaselineOffsetAttributeName:@(-3)}];
                label.attributedText = att1;
            }
            else
            {
                label.text = @"";
            }
        }
    }
    self.textField.text = text;
    self.currentText = text;
}

//block回调拿到输入的密码字符

- (void)textDidChanged:(UITextField *)textField
{
    if (textField.text.length > PasswordBoxNumber)
    {
        textField.text = [textField.text substringToIndex:PasswordBoxNumber];
    }
    
    [self updateLabelBoxWithText:textField.text];
    if (textField.text.length == PasswordBoxNumber)
    {
        if (self.completionBlock)
        {
            self.completionBlock(self.textField.text);
        }
    }
}

demo下载地址：https://github.com/dt8888/PursePossword
##三.demo 的使用
1.初始化试图

self.payPopupView = [[PursePopupView alloc]initWithFrame:CGRectMake(0, XX_6(310), kScreenWidth, kScreenHeight)];
 self.payPopupView.delegate = self;
 [self.payPopupView showPayPopView];

2.实现代理方法拿到输入密码字符串

- (void)didPasswordInputFinished:(NSString *)password
{
    if ([password isEqualToString:@"123456"])
    {
        NSLog(@"输入的密码正确");
    }
    else
    {
        NSLog(@"输入错误:%@",password);
        [self.payPopupView didInputPayPasswordError];
    }
}