美文网首页
让UIScrollerview一直显示滚动条

让UIScrollerview一直显示滚动条

作者: AngeloD | 来源:发表于2019-09-26 21:42 被阅读0次

    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
    

    这两个属性默认是YES, 显示水平和垂直滚动条, 只有当我们滚动的时候显示,当我们不滚动时,慢慢淡出

    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
    };
    

    这个属性默认是UIScrollViewIndicatorStyleDefault, 第二个属性UIScrollViewIndicatorStyleBlack 滚动条是黑色, 第三个属性UIScrollViewIndicatorStyleWhite 滚动条是白色

    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. 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 < 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. 写完分类之后, 我们在初始化UIScrollView的时候设置UIScrollView的tag为836913

    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.
      

      即调用以下方法

      [scrollView reloadData];
      [scrollView layoutIfNeeded]; // 第一次进来时没有显示出来,可能是UI没有更新,添加这句,等reloadData刷新完之后,更新UI;
      [scrollView flashScrollIndicators];
      

    相关文章

      网友评论

          本文标题:让UIScrollerview一直显示滚动条

          本文链接:https://www.haomeiwen.com/subject/pvrmyctx.html