iOS开发-UIScrollView原理
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转载:http://www.cnblogs.com/xiaofeixiang/p/5144256.html
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]; }
@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~
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