iOS 实现金融选金额的游标尺

最近产品看别的app有游标尺选金额，要我们也加上，好吧，开干！先看看效果：

首先我要可以设置最大值、最小值、和默认指向的值：

@property (nonatomic, assign) double minValue;      // 最小值，默认为0
@property (nonatomic, assign) double maxValue;      // 最大值，必需设置
@property (nonatomic, assign) double defaultValue;  // 默认值，默认为0

初始化试图：

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        _scrollWidth = kScreenWidth;
        self.backgroundColor = [UIColor whiteColor];
        [self addSubview:self.scrollView];
        [self addSubview:self.textField];
        [self addSubview:self.markLine];
        [self addSubview:self.bottomLine];
        _minValue = 0;     //设置默认初始值
    }
    return self;
}

难点是根据数值画刻度：

- (void)createIndicator{
    for (NSUInteger i = self.minValue, j = 0; i <= self.maxValue; i+=kMinScale, j++) {
        _scrollWidth += kPadding;
        [self drawSegmentWithValue:i idx:j];
    }
    self.scrollView.contentSize = CGSizeMake(_scrollWidth-kPadding, CGRectGetHeight(self.frame));
}

- (void)drawSegmentWithValue:(NSUInteger)value idx:(NSUInteger)idx {
    UIBezierPath *path = [UIBezierPath bezierPath];
    CGFloat x = kScreenWidth*0.5 + kPadding*idx;
    [path moveToPoint:CGPointMake(x, CGRectGetHeight(self.frame)-5)];

    if (value % (kMinScale*10) == 0 || value == _minValue) { //每10个刻度，do something
        [path addLineToPoint:CGPointMake(x, CGRectGetHeight(self.frame)-10-5-10)];
        UILabel *numLabel = [[UILabel alloc] initWithFrame:CGRectMake(x-50*0.5, CGRectGetHeight(self.frame)-20-10-5-5, 50, 10)];
        numLabel.font = [UIFont systemFontOfSize:12];
        numLabel.textAlignment = NSTextAlignmentCenter;
        numLabel.textColor = [UIColor redColor];
        numLabel.text = [NSString stringWithFormat:@"%ld", value];
        [self.scrollView addSubview:numLabel];
    } else if (value % (kMinScale*2) != 0) {   //每2个刻度，do something
        [path addLineToPoint:CGPointMake(x, CGRectGetHeight(self.frame)-10)];
    } else{
        [path addLineToPoint:CGPointMake(x, CGRectGetHeight(self.frame)-10-5)];
    }

    CAShapeLayer *line = [[CAShapeLayer alloc] init];
    line.lineWidth = 1;
    line.strokeColor = [UIColor orangeColor].CGColor;
    line.path = path.CGPath;

    [self.scrollView.layer addSublayer:line];
}

通过执行UIScrollViewDelegate实时显示滚到的数值

#pragma mark - UIScrollViewDelegate
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    CGFloat num = scrollView.contentOffset.x;
    double value = (num / kPadding) * kMinScale + self.minValue;
    if (value < self.minValue) {
        value = self.minValue;
    }else if (value > self.maxValue) {
        value = self.maxValue;
    }

    self.textField.text = [NSString stringWithFormat:@"%.f", value];
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
    CGFloat num = scrollView.contentOffset.x;
    NSInteger value = (num / kPadding) * kMinScale + self.minValue;
    value =  value - value % kMinScale;
    [self.scrollView setContentOffset:CGPointMake((value-_minValue)/kMinScale*kPadding, 0) animated:YES];
    self.textField.text = [NSString stringWithFormat:@"%ld", value];
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
    if(!decelerate){
        //OK,真正停止了，do something
        CGFloat num = scrollView.contentOffset.x;
        NSInteger value = (num / kPadding) * kMinScale + self.minValue;
        value =  value - value % kMinScale;
        [self.scrollView setContentOffset:CGPointMake((value-_minValue)/kMinScale*kPadding, 0) animated:YES];
        self.textField.text = [NSString stringWithFormat:@"%ld", value];
    }
}

通过实现UITextFieldDelegate代理方法实现数值修改，让游标尺滚动到对应的数值：

#pragma mark - UITextFieldDelegate
- (BOOL)textFieldShouldReturn:(UITextField *)textField {
    [self endEditing:YES];
    return YES;
}

- (void)textFieldDidEndEditing:(UITextField *)textField {
    if (textField.text.doubleValue > self.maxValue) {
        textField.text = [NSString stringWithFormat:@"%.f",self.maxValue];
    }

    [self.scrollView setContentOffset:CGPointMake((textField.text.doubleValue-_minValue)/kMinScale*kPadding, 0) animated:YES];
    self.textField.text = textField.text;
}

// 根据输入的数字变化
- (void)textDidChanged:(NSNotification *)info {
    UITextField *textField = info.object;
    NSString *text = textField.text;
    if (textField.isEditing) {
        self.scrollView.contentOffset = CGPointMake((text.doubleValue-_minValue)/kMinScale*kPadding, 0);
        self.textField.text = text;
    }
}

细节处理：游标尺自动取整
一个简洁的游标尺，就实现了。这里将Demo：ZBRulerView献上，朋友请多指教。