UITableView拉伸效果

创建一个UITableView 和一个UIImageView

@property (nonatomic, strong) UITableView *tableView;

@property (nonatomic, strong) UIImageView *headerImgaeView;

初始化

 1 - (void)viewDidLoad {
 2     [super viewDidLoad];
 3 
 4     self.tableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 0, 320, 568) style:UITableViewStyleGrouped];
 5     self.tableView.delegate = self;
 6     self.tableView.dataSource = self;
 7     [self.view addSubview:self.tableView];
 8     
 9     
10     [self layoutHeaderImageView];
11 }

viewDidLoad

layoutHeaderImageView

 1 - (void)layoutHeaderImageView
 2 {
 3     UIView *headerBackView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 150)];
 4     headerBackView.backgroundColor = [UIColor lightGrayColor];
 5     self.tableView.tableHeaderView = headerBackView;
 6     
 7     self.headerImgaeView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 150)];
 8     self.headerImgaeView.backgroundColor = [UIColor greenColor];
 9     self.headerImgaeView.image = [UIImage imageNamed:@"beautiful.jpg"];
10     self.headerImgaeView.contentMode = UIViewContentModeScaleAspectFill;
11     self.headerImgaeView.clipsToBounds = YES;
12     [headerBackView addSubview:self.headerImgaeView];
13 
14 }

layoutHeaderImageView

滚动偏移的主要方法（这个为UIScrollViewDelegate中的代理方法）

 1 - (void)scrollViewDidScroll:(UIScrollView *)scrollView
 2 {
 3     CGFloat width = self.view.frame.size.width;// 图片宽度
 4     CGFloat yOffset = scrollView.contentOffset.y; //偏移量
 5     
 6     NSLog(@":  %.2f", yOffset);
 7     
 8     if (yOffset < 0) {
 9         CGFloat totalOffset = 150 + ABS(yOffset);
10         CGFloat f = totalOffset / 150; //缩放系数
11         
12         self.headerImgaeView.frame = CGRectMake(-(width * f - width) / 2, yOffset, width * f, totalOffset); //拉伸后的frame是同比例缩放
13     }
14     
15     if (yOffset > 0) {
16         CGFloat totalOffset = 150 - ABS(yOffset);
17         CGFloat f = totalOffset / 150;
18         
19         self.headerImgaeView.frame = CGRectMake(-(width * f - width) / 2, yOffset, width * f, totalOffset);
20     }
21 }

scrollView