UIScrollView代理方法的实现

1.开始滑动
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    NSLog(@"scrollViewWillBeginDragging");
}
2.将要结束滑动
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inoutCGPoint
*)targetContentOffset NS_AVAILABLE_IOS(5_0)
{
    NSLog(@"scrollViewWillEndDragging");
}
注意该方法常用在当用户滚动完屏幕时加载图片，HTTP请求加载，这样会提高效率

3.已经结束滑动
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
    NSLog(@"scrollViewDidEndDragging");
}
4.将要减速
- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView
{
    NSLog(@"scrollViewWillBeginDecelerating");
}
5.已经减速
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView   // called when scroll view grinds to a halt
{
    NSLog(@"scrollViewDidEndDecelerating");
}
6.已经停止滚动
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView
{
    NSLog(@"scrollViewDidEndScrollingAnimation");
}
isMemberOfClass和isKindOfClass的异同
两者都能检测出一个对象是否是某个类的成员，区别是：
isKindOfClass不但可以检测出一个对象是否是某一类的成员，也可以确定一个对象是否是派生自该类的成员，而isMemberOfClass不行

7.用代理方法实现图片的放大缩小

-(void)viewDidLoad
{
ScrollView=[[[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)] autorelease];
ScrollView.delegate=self;
ScrollView.backgroundColor=[UIColor redColor];
ScrollView.scrollsToTop=YES;
ScrollView.contentSize=CGSizeMake(320, 460);
ScrollView.maximumZoomScale=2;
ScrollView.minimumZoomScale=0.5;
ScrollView.backgroundColor=[UIColor yellowColor];
[self.view addSubview:ScrollView];

imageView=[[[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)] autorelease];
imageView.image=[UIImage imageNamed:@"image1.jpg"];
[ScrollView addSubview:imageView];

}

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
return imageView;
}
- (void)scrollViewWillBeginZooming:(UIScrollView *)scrollView withView:(UIView *)view NS_AVAILABLE_IOS(3_2)
{
NSLog(@"begin scrollview");
}
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale
{
NSLog(@"did  end  finih");
}