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:
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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];
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重新设置Bounds:
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CGRect bounds=self.container.bounds;
bounds.origin=CGPointMake(0, 200);
self.container.bounds=bounds;
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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:
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@
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
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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:
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-(
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];
}
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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
