iOS开发之UIScrollView

iOS笔记

什么是UIScrollView

UIScrollView是iOS开发中最常用的控件之一，是UITableView和UICollectionView的直接父类。

UIScrollView无法滚动的可能原因

• 没有设置contentSize
• 什么是UIScrollView
• 没有接收到触摸事件:userInteractionEnabled = NO

UIScrollView的三个常见属性

查看UIScrollView的头文件

@property(nonatomic) CGPoint contentOffset;         // default CGPointZero
@property(nonatomic) CGSize contentSize;            // default CGSizeZero
@property(nonatomic) UIEdgeInsets contentInset;     // default UIEdgeInsetsZero. add additional scroll area around content

contentOffset这个属性用来表示UIScrollView滚动的位置
（其实就是内容左上角与scrollView左上角的间距值）
contentSize这个属性用来表示UIScrollView内容的尺寸，滚动范围（能滚多远）
contentInset这个属性能够在UIScrollView的4周增加额外的滚动区域，一般用来避免scrollView的内容被其他控件挡住

UIScrollView的其他属性

@property(nonatomic) BOOL bounces;
// 设置UIScrollView是否需要弹簧效果
@property(nonatomic,getter=isScrollEnabled) BOOL scrollEnabled; 
// 设置UIScrollView是否能滚动
@property(nonatomic) BOOL showsHorizontalScrollIndicator;
// 是否显示水平滚动条
@property(nonatomic) BOOL showsVerticalScrollIndicator;
// 是否显示垂直滚动条

UIScrollView的代理

打开UIScrollViewDelegate的头文件，可以看到一堆代理方法

常用的代理方法有
- (void)scrollViewDidScroll:(UIScrollView *)scrollView;                                               // any offset changes
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView;
// called on finger up if the user dragged. velocity is in points/millisecond. targetContentOffset may be changed to adjust where the scroll view comes to rest
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset NS_AVAILABLE_IOS(5_0);
// called on finger up if the user dragged. decelerate is true if it will continue moving afterwards
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate;
- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView;   // called on finger up as we are moving
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView;      // called when scroll view grinds to a halt
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView; // called when setContentOffset/scrollRectVisible:animated: finishes. not called if not animating

UIScrollView的其他用法

内容缩放
分页

取消系统自动调节

self.automaticallyAdjustsScrollViewInsets = NO;