iOS导航栏自由缩放头像效果

效果图:

 

 

上代码:

先给一个self.navigationItem.titleView ，然后再放个ImangeView添加到titleView上:

   UIView *titleView = [[UIView alloc] init];
    self.navigationItem.titleView = titleView;
    
    self.headImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"timg.jpg"]];
    self.headImageView.frame = CGRectMake(0, 0, 80, 80);
    self.headImageView.layer.cornerRadius = 40;
    self.headImageView.layer.masksToBounds = YES;
    //保证头像水平居中
    self.headImageView.center = CGPointMake(titleView.center.x, 0);
    [titleView addSubview:self.headImageView];

核心代码：

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    CGFloat scale = 1.0;
    NSLog(@"y======%.2f---top======%.2f",scrollView.contentOffset.y,scrollView.contentInset.top);
    CGFloat offsetY = scrollView.contentOffset.y + scrollView.contentInset.top;
    NSLog(@"offsetY=======%.2f",offsetY);

    if (offsetY < 0) { // 放大
        // 允许下拉放大的最大距离为330
        // 1.5是放大的最大倍数
        // 这个值可以自由调整
        scale = MIN(1.5, 1 - offsetY / 330);
    } else if (offsetY > 0) { // 缩小
        // 允许向上超过导航条缩小的最大距离为330
        // 为了防止缩小过度，给一个最小值为0.50
        scale = MAX(0.50, 1 - offsetY / 330);
    }
    
    self.headImageView.transform = CGAffineTransformMakeScale(scale, scale);

    // 保证缩放后y坐标不变
    CGRect frame = self.headImageView.frame;
    frame.origin.y = -self.headImageView.layer.cornerRadius / 2;
    self.headImageView.frame = frame;

}

 

Demo地址:https://github.com/domanc/HeadImageScale.git

 

转载于:https://www.cnblogs.com/dianming/p/6648255.html