Swift语言实现下拉变大效果：（上拉缩小效果随后研究......）

关键代码：方法一：

self.automaticallyAdjustsScrollViewInsets = false;
        
        tableViewW = UITableView.init(frame: CGRectMake(0, 0, screenWidth(), screenHeight()), style: .Plain);
        tableViewW.delegate = self;
        tableViewW.dataSource = self;
        tableViewW.showsVerticalScrollIndicator = false;
        tableViewW.tableFooterView = UIView.init();
        //下面两句话是关键点，并且顺序不能错，否则初始化运行的时候图片显示不完全
        tableViewW.contentInset = UIEdgeInsetsMake(200, 0, 0, 0);
        tableViewW.contentOffset = CGPointMake(0, -200);
        if tableViewW.respondsToSelector(Selector("setLayoutMargins:"))
        {
            tableViewW.layoutMargins = UIEdgeInsetsZero;
        }
        if tableViewW.respondsToSelector(Selector("setSeparatorInset:"))
        {
            tableViewW.separatorInset = UIEdgeInsetsZero;
        }
        self.view.addSubview(tableViewW);
        
        headView = UIImageView.init(frame: CGRectMake(0, -200, screenWidth(), 200));
        headView.image = UIImage.init(named: "33.jpg");
        //这句话是关键点设置高度改变宽度也改变
        headView.contentMode = UIViewContentMode.ScaleAspectFill;
        tableViewW.addSubview(headView);

实现UIScrollView的代理方法:

func scrollViewDidScroll(scrollView: UIScrollView) {
        let offSetY:CGFloat = scrollView.contentOffset.y;//当这里有导航条的时候:+NavigationBarHeight
        if offSetY < -200
        {
            //下拉，图片放大
            var frameE:CGRect = headView.frame;
            frameE.origin.y = offSetY;
            frameE.size.height = -offSetY;//contentMode = UIViewContentModeScaleAspectFill;时，高度改变宽度也改变
            headView.frame = frameE;
            
        }

OC语言运用第二种方法实现，图片的下拉放大，下拉缩小的效果

关键代码：

self.title = @"下拉变大，上拉缩小";
    self.automaticallyAdjustsScrollViewInsets = NO;
    
    _myTableView = [[UITableView alloc]initWithFrame:CGRectMake(0, navHeight, screenWidth, screenHeight - navHeight)];
    _myTableView.delegate = self;
    _myTableView.dataSource = self;
    _myTableView.contentInset = UIEdgeInsetsMake(headViewRect.size.height-navHeight-navHeight, 0, 0, 0);
    [self.view addSubview:_myTableView];
    
    _myView = [[HeadView alloc]initWithFrame:headViewRect backgroundView:@"22.jpg" headView:@"sun.png" headViewWidth:(CGFloat)(screenWidth / 4) signLabel:@"用户名：太阳*黑子"];
    _myView.backgroundColor = [UIColor clearColor];
    _myView.userInteractionEnabled = NO;
    [self.view addSubview:_myView];
    
    UIButton *backBtn = [UIButton buttonWithType:UIButtonTypeCustom];
    backBtn.frame = CGRectMake(20, 20, 60, 44);
    [backBtn setTitle:@"<<返回" forState:UIControlStateNormal];
    [backBtn setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
    [backBtn addTarget:self action:@selector(backBtnClick) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:backBtn];

实现UIScrollView的方法：

#pragma mark ------- UIScrollViewDelegate
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
    
    CGFloat offset_Y = scrollView.contentOffset.y + headViewRect.size.height-navHeight-navHeight;
    
    if  (offset_Y < 0) {
        //下拉图片放大
        _myView.backgroundView.contentMode = UIViewContentModeScaleToFill;
        
        _myView.backgroundView.frame = CGRectMake(offset_Y*0.5 , -navHeight, screenWidth - offset_Y, headViewRect.size.height - offset_Y);
    }else if (offset_Y > 0 && offset_Y <= (headViewRect.size.height-navHeight-navHeight)) {
        //下拉图片缩小，并改变图片的显示效果
        _myView.backgroundView.contentMode = UIViewContentModeTop;
        
        _myView.backgroundView.frame = CGRectMake(0 ,navHeight* offset_Y/(headViewRect.size.height-navHeight-navHeight)-navHeight , screenWidth , headViewRect.size.height -(navHeight + navHeight* offset_Y/(headViewRect.size.height-navHeight-navHeight)-navHeight) - offset_Y);
        
        
        CGFloat width = offset_Y*(40-(screenWidth / 4))/(headViewRect.size.height-navHeight-navHeight)+(screenWidth / 4);
        _myView.headView.frame =CGRectMake(0, 0, width,width);
        _myView.headView.layer.cornerRadius =width*0.5;
        _myView.headView.center = _myView.backgroundView.center;
        
        _myView.signLabel.frame =CGRectMake(0, CGRectGetMaxY(_myView.headView.frame), screenWidth, 40);
        
        _myView.signLabel.alpha = 1 - (offset_Y*3 / (headViewRect.size.height-navHeight-navHeight) /2);
    }
}

效果图：

     

Demo下载：http://download.csdn.net/detail/hbblzjy/9606681