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iOS开发-UIScrollView原理

日期：2017-06-27点击：251收藏

UIScrollView在开发中是不可避免，关于UIScrollView都有自己一定的理解。滚动视图有两个需要理解的属性，frame和bounds，frame是定义了视图在窗口的大小和位置，bounds表示视图在其自身坐标系中的位置和大小，frame影响视图在窗口位置，bounds会影响子视图的位置。

先来看一张图片:

我们用一个父View将整个窗口铺满，然后添加子视图:

     UIView *redView = [[UIView alloc] initWithFrame:CGRectMake(20, 20, 100, 100)]; 
 redView.backgroundColor = [UIColor redColor]; 
   
 UIView *greenView = [[UIView alloc] initWithFrame:CGRectMake(160, 150, 150, 180)]; 
 greenView.backgroundColor = [UIColor greenColor]; 
   
 UIView *blueView = [[UIView alloc] initWithFrame:CGRectMake(60, 400, 200, 150)]; 
 blueView.backgroundColor = [UIColor blueColor]; 
   
 UIView *yellowView = [[UIView alloc] initWithFrame:CGRectMake(180, 600, 180, 200)]; 
 yellowView.backgroundColor = [UIColor yellowColor]; 
   
 [self.container addSubview:redView]; 
 [self.container addSubview:greenView]; 
 [self.container addSubview:blueView]; 
 [self.container addSubview:yellowView]; 
 UILabel *desc=[[UILabel alloc]initWithFrame:CGRectMake(150, 20, 200, 20)]; 
 [desc setText: @"博客园-FlyElephant" ]; 
 [desc setFont:[UIFont systemFontOfSize:14]]; 
 [desc setTextAlignment:NSTextAlignmentCenter]; 
 [self.container addSubview:desc]; 
   [self.view addSubview:self.container]; 
 
  

重新设置Bounds:

     CGRect bounds=self.container.bounds; 
 bounds.origin=CGPointMake(0, 200); 
 self.container.bounds=bounds; 
 
  

效果如下:

通过设置Bounds可以让视图向上移动，那么我可以通过手势简单的定义UIScrollView:

     @ interface   FEScrollView() 
   
 @property (assign,nonatomic) CGSize contentSize; 
   
 @end 
   
 @implementation FEScrollView 
   
 -(instancetype)initWithFrame:(CGRect)frame{ 
      self=[super initWithFrame:frame]; 
      if  (self) { 
          UIPanGestureRecognizer *panGesture=[[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(handlePanGesture:)]; 
          [self addGestureRecognizer:panGesture]; 
      } 
      return  self; 
 } 
   
 -( void )handlePanGesture:(UIPanGestureRecognizer *)panGestureRecongnizer{ 
      CGPoint translation = [panGestureRecongnizer translationInView:self]; 
      CGRect bounds = self.bounds; 
       
      CGFloat newBoundsOriginY = bounds.origin.y - translation.y; 
      bounds.origin.y=newBoundsOriginY; 
      self.bounds = bounds; 
     
      [panGestureRecongnizer setTranslation:CGPointZero inView:self]; 
 }<br>@end 
 
  

效果如下:

UIScrollView是可以设置ConteSize的，我们也可以设置,并控制滑动的范围:

     -( void )handlePanGesture:(UIPanGestureRecognizer *)panGestureRecongnizer{ 
      CGPoint translation = [panGestureRecongnizer translationInView:self]; 
      CGRect bounds = self.bounds; 
       
      //需要设置contentsize 
      CGFloat newBoundsOriginX = bounds.origin.x - translation.x; 
      CGFloat minBoundsOriginX = 0.0; 
      CGFloat maxBoundsOriginX = self.contentSize.width - bounds.size.width; 
      bounds.origin.x = fmax(minBoundsOriginX, fmin(newBoundsOriginX, maxBoundsOriginX)); 
       
      CGFloat newBoundsOriginY = bounds.origin.y - translation.y; 
      CGFloat minBoundsOriginY = 0.0; 
      CGFloat maxBoundsOriginY = self.contentSize.height - bounds.size.height; 
      bounds.origin.y = fmax(minBoundsOriginY, fmin(newBoundsOriginY, maxBoundsOriginY)); 
     
      self.bounds = bounds; 
      [panGestureRecongnizer setTranslation:CGPointZero inView:self]; 
 } 
 
  

UIScrollView实际上比我们实现的要复杂很多反弹效果，动量滚动，放大试图以及涉及到的代理方法，本文就是简单介绍一下原理，实际开发中如非特殊的必要，没必要继承UIView去实现UIScrollView。如果对UIScrollView有特殊需求，倒是可以继承UIScrollView实现自己的功能~

本文转自Fly_Elephant博客园博客，原文链接：http://www.cnblogs.com/xiaofeixiang/p/5144256.html，如需转载请自行联系原作者

原文链接：https://yq.aliyun.com/articles/362306

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