一.UIScrollView顯示或者隱藏滾動條, 默認有兩個屬性

@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

這兩個屬性默認是YES, 顯示水平和垂直滾動條, 只有當我們滾動的時候顯示,當我們不滾動時,慢慢淡出

二.UIScrollView滾動條的樣式, 默認有三個樣式

@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
};

這個屬性默認是UIScrollViewIndicatorStyleDefault, 第二個屬性UIScrollViewIndicatorStyleBlack 滾動條是黑色, 第三個屬性UIScrollViewIndicatorStyleWhite 滾動條是白色

三.UIScrollView滾動條的偏移量

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

四.UIScrollView滾動條一直顯示

1. 滾動條是一個UIImageView, 滾動條隱藏是因為設置了alpha屬性為0, 所有我們寫一個UIImageView的分類

   
   #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 < sc.contentSize.height) {
                       return;
                   }
               }
           }
       }
        
       if (self.superview.tag == noDisableHorizontalScrollTag) {
           if (alpha == 0 && self.autoresizingMask == UIViewAutoresizingFlexibleTopMargin) {
               if (self.frame.size.height < 10 && self.frame.size.height < self.frame.size.width) {
                   UIScrollView *sc = (UIScrollView*)self.superview;
                   if (sc.frame.size.width < sc.contentSize.width) {
                       return;
                   }
               }
           }
       }
       
       [super setAlpha:alpha];
   }
   @end
   
   

2. 寫完分類之后, 我們在初始化UIScrollView的時候設置UIScrollView的tag為836913

3. 要在UIScrollView數(shù)據(jù)綁定之后, 調用以下方法

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

   即調用以下方法

   [scrollView reloadData];
   [scrollView layoutIfNeeded]; // 第一次進來時沒有顯示出來由缆，可能是UI沒有更新注祖，添加這句猾蒂，等reloadData刷新完之后，更新UI是晨；
   [scrollView flashScrollIndicators];