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iOS开发-UIScrollView原理

日期：2017-06-27点击：566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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