iOS开发中UIScrollView始终显示滚动条及其相关属性详解

一.UIScrollView显示或者隐藏滚动条, 默认有两个属性

@property(nonatomic)         BOOL                         showsHorizontalScrollIndicator; // default YES. show indicator while we are tracking. fades out after tracking

@property(nonatomic)         BOOL                         showsVerticalScrollIndicator;   // default YES. show indicator while we are tracking. fades out after tracking

二.UIScrollView滚动条的样式, 默认有三个样式

@property(nonatomic)         UIScrollViewIndicatorStyle   indicatorStyle;                 // default is UIScrollViewIndicatorStyleDefault

typedef NS_ENUM(NSInteger, UIScrollViewIndicatorStyle) {    UIScrollViewIndicatorStyleDefault,     // black with white border. good against any background    UIScrollViewIndicatorStyleBlack,       // black only. smaller. good against a white background    UIScrollViewIndicatorStyleWhite        // white only. smaller. good against a black background};

三.UIScrollView滚动条的偏移量

@property(nonatomic)         UIEdgeInsets                 scrollIndicatorInsets;          // default is UIEdgeInsetsZero. adjust indicators inside of insets

四.UIScrollView滚动条一直显示

1.我们知道滚动条是一个UIImageView, 滚动条隐藏是因为设置了alpha属性为0, 所有我们写一个UIImageView的分类

#define noDisableVerticalScrollTag 836913
#define noDisableHorizontalScrollTag 836914

@implementation UIImageView (WLScrollView)

- (void)setAlpha:(CGFloat)alpha 
{

if (self.superview.tag == noDisableVerticalScrollTag) {
    if (alpha == 0 && self.autoresizingMask == UIViewAutoresizingFlexibleLeftMargin) {
        if (self.frame.size.width <10 && self.frame.size.height > self.frame.size.width) {
            UIScrollView *sc = (UIScrollView*)self.superview;
            if (sc.frame.size.height                 return;
            }
        }
    }
}

if (self.superview.tag == noDisableHorizontalScrollTag) {
    if (alpha == 0 && self.autoresizingMask == UIViewAutoresizingFlexibleTopMargin) {
        if (self.frame.size.height <10 && self.frame.size.height             UIScrollView *sc = (UIScrollView*)self.superview;
            if (sc.frame.size.width                 return;
            }
        }
    }
}

[super setAlpha:alpha];
}
@end

3.要在UIScrollView数据绑定之后, 调用以下方法

- (void)flashScrollIndicators;             // displays the scroll indicators for a short time. This should be done whenever you bring the scroll view to front.

[scrollView reloadData];
[scrollView flashScrollIndicators];