UIScrollView

UIScollView

创建一个简单的UIScollView

在viewDidLoad中实现如下代码

  UIScrollView *scroll = [[UIScrollView alloc]init];
  scroll.frame = self.view.frame;
    //设置代理
    scroll.delegate = self;
    scroll.backgroundColor=[UIColor redColor];//设置颜色

    [self.View addSubView:scroll];

实现代理:UIScrollViewDelegate

• -(void)scrollViewDidScroll:(UIScrollView *)scrollView; //scrollView已经开始滑动
• • (void)scrollViewDidZoom:(UIScrollView *)scrollView;//开始缩放 放大或缩小
• • (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView;将要开始滑动
• • (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate;//scrollVIew已经结束滑动
• • (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView; //将要开始减速
• • (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView; //已经结束减速
• • (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView;//滑动的动画已经结束
• • (BOOL)scrollViewShouldScrollToTop:(UIScrollView *)scrollView;//返回yes的时候,返回到顶部 同理还有一个属性scrollsToTop=YES时,避免头部出现空白视图;
• • (void)scrollViewWillBeginZooming:(UIScrollView *)scrollView withView:(nullable UIView *)view;//将要开始缩放

一个实现图片缩放的简单代码

  
- (void)viewDidLoad
{
    [super viewDidLoad];
    //模拟器上实现缩放 点option
    UIScrollView *scroll = [[UIScrollView alloc]init];
    scroll.frame = self.view.frame;
    //设置代理
    scroll.delegate = self;
    scroll.backgroundColor=[UIColor redColor];
    [self.view addSubview:scroll];
    //最大缩放比例
    scroll.maximumZoomScale = 3.0;
    //最小缩放比例
    scroll.minimumZoomScale = 0.5;
    
    
    _imgview = [[UIImageView alloc]init];
    _imgview.frame = CGRectMake(0, 0, 320, 480);
    _imgview.image = [UIImage imageNamed:@"sun.png"];
    [scroll addSubview:_imgview];
    
    
    
    // Do any additional setup after loading the view, typically from a nib.
}
/*
 实现缩放的3步:
 1.设置最大缩放比例要大于最小缩放比例
 2.设置代理
 3.实现协议方法viewForZoomoingInScrollView 在这里要返回要进行缩放的子视图
 */


-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
    //返回要进行缩放的scrollview的子视图
    return _imgview;
    
    
}

使用NSTimer和UIScrollVIew实现一个图片轮播器,第一张-->第五张-->第一张

.h
@interface ViewController : UIViewController
{
    int _speed;//记录方向
    UIScrollView *_scroll;//
    NSTimer *_timer;//计时器
    
   
    float _offsetStartDrag; //开始拖动时,偏移量大小
}
@end

.m

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    UIScrollView *scroll = [[UIScrollView alloc]init];
    scroll.delegate = self;
    scroll.frame = CGRectMake(0, 0, 320, 480);
    [self.view addSubview:scroll];
    
    for (int i = 0; i < 5; i ++) {
        UIImageView *imgview = [[UIImageView alloc]init];
        imgview.frame = CGRectMake(320*i, 0, 320, 480);
        imgview.image = [UIImage imageNamed:[NSString stringWithFormat:@"fight%d",i+1]];
        [scroll addSubview:imgview];
        
    }
    
    scroll.contentSize = CGSizeMake(320*5, 480);
    scroll.pagingEnabled = YES;
    _scroll = scroll;
    
    
    _timer = [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(onTimer) userInfo:nil repeats:YES];
    _speed = 320;
}

-(void)onTimer {
    
    
    
    float offset = _scroll.contentOffset.x;
    
    if (offset >= 320*4) {
        //已经到达最右边
        _speed = -320;
    }
    else if (offset <= 0){
        //已经到达最左边
        _speed = 320;
    }
    
    offset += _speed;
    
    [_scroll setContentOffset:CGPointMake(offset, 0) animated:YES];
    
    
}

-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    //当用户开始拖动scrollview时,让定时器暂停
    [_timer setFireDate:[NSDate distantFuture]];
    
    
    //记录开始拖动时的偏移量 目的跟结果拖动的偏移量进行比较
    
    _offsetStartDrag = scrollView.contentOffset.x;
    
}

-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
    //得到结束拖动到偏移量
    float offsetEndDrag = scrollView.contentOffset.x;
    
    if (_offsetStartDrag <= offsetEndDrag) {
        //向右拖动
        _speed = 320;
    }
    else{
        _speed = -320;
    }
    
}



-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    //当scrollview停止滚动时,2.0秒之后重新开启定时器
    [_timer setFireDate:[NSDate dateWithTimeIntervalSinceNow:2.0]];
}
@end

配合图片轮播的一个黄金搭档-UIPageControl

初始化创建
_pgctl = [[UIPageControl alloc]init];
    _pgctl.backgroundColor = [UIColor redColor];//
    _pgctl.frame = CGRectMake(0, 20, 320, 20);
    _pgctl.numberOfPages = 5;//显示的页码个数
    [_pgctl addTarget:self action:@selector(onPgctlClick) forControlEvents:UIControlEventValueChanged];//点击时绑定的方法
    [self.view addSubview:_pgctl];
    

-(void)onPgctlClick {//实现方法
   [_timer setFireDate:[NSDate distantFuture]];//将计时器关闭
    float offset = _pgctl.currentPage*320;//记录点击时scroll需要的偏移量
    
    [_scroll setContentOffset:CGPointMake(offset, 0) animated:YES];//将scroll滑动到指定的位置;
    
    [self performSelector:@selector(timerreStart) withObject:nil afterDelay:2.0];//两秒之后执行计时器;
    /*performSelector的使用理解请结合runtime特性:
    它要执行的方法在编译接单,如果没有实现,是不会报错的,但是执行时会崩溃,还有runLoop.... */
}
#pragma mark 启动计时器的方法
-(void)timerreStart {
    [_timer setFireDate:[NSDate dateWithTimeIntervalSinceNow:1]];
}


-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    //当scrollview停止滚动时,2.0秒之后重新开启定时器
    [_timer setFireDate:[NSDate dateWithTimeIntervalSinceNow:2.0]];
    
    
    _pgctl.currentPage = scrollView.contentOffset.x/320;
    
}


-(void)onTimer {//计时器的绑定方法
    float offset = _scroll.contentOffset.x;
    
    if (offset >= 320*4) {
        //已经到达最右边
        _speed = -320;
    }
    else if (offset <= 0){
        //已经到达最左边
        _speed = 320;
    }
    
    offset += _speed;
    
    [_scroll setContentOffset:CGPointMake(offset, 0) animated:YES];

    _pgctl.currentPage = offset/320;    
}