ScrollView高级特性

- (void)viewDidLoad {
    [super viewDidLoad];
    //滚动视图，可以对屏幕内容进行滚屏查看。
    
    _scrollView = [[UIScrollView alloc]init];
    
    _scrollView.frame = CGRectMake(10, 50, 300, 400);
    
    _scrollView.bounces = YES;
    
    //是否允许通过点击屏幕让滚动视图响应事件
    _scrollView.userInteractionEnabled = YES;
    
    //设置画布大小，纵向效果
    _scrollView.contentSize = CGSizeMake(300, 400*3);
    
    
    for(int i=0 ;i<3;i++)
    {
        //生成图片名称
        NSString* strName = [NSString stringWithFormat:@"%d.jpg",i+1];
        
        UIImage* image = [UIImage imageNamed:strName];
        
        //创建视图对象
        UIImageView* iView = [[UIImageView alloc]init];
        //图像赋值
        iView.image = image;
        //设置图像试图在滚动视图画布中的位置
        iView.frame = CGRectMake(0, 400*i, 300, 400);
        
        [_scrollView addSubview:iView];
        
    }
    
    [self.view addSubview:_scrollView];
    
    //取消按页滚动效果
    _scrollView.pagingEnabled = NO;
    
    //滚动视图画布的移动位置，偏移位置
    _scrollView.contentOffset = CGPointMake(0, 0);
    //将当前视图控制器作为代理对象
    _scrollView.delegate = self;
    
}

-(void) touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
//    _scrollView.contentOffset = CGPointMake(0, 0);
    
    //带有动画效果的，移动到指定位置
    
    [_scrollView scrollRectToVisible:CGRectMake(0, 600, 300, 400) animated:YES];
    
}


//可以使用此函数，监控滚动视图的位置
-(void) scrollViewDidScroll:(UIScrollView *)scrollView
{
    NSLog(@"y = %f",scrollView.contentOffset.y);
}

//由此，我在这里总结一共几个事件
//拖动：即将开始拖动，即将结束拖动，已经结束拖动。后两者是连贯的
//减速：即将开始减速，已经结束减速
-(void) scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
    NSLog(@"已经结束拖动");
}

-(void) scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    NSLog(@"即将开始拖动");
}

-(void) scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
{
    NSLog(@"即将结束拖动");
}

-(void) scrollViewWillBeginDecelerating:(UIScrollView *)scrollView
{
    NSLog(@"视图即将开始减速");
}

//视图停止时调用
-(void) scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    NSLog(@"视图已经结束减速");
}

@interface ViewController : UIViewController<UIScrollViewDelegate>
{
    //当前视图控制器要实现的协议函数
    //定义一个滚动视图成员变量
    UIScrollView* _scrollView;
    
    
}