UIScrollview使用

改变内容偏移

- (void)setContentOffset:(CGPoint)contentOffset animated:(BOOL)animated;  // animate at constant velocity to new offset

显示contentsize中的某部分

- (void)scrollRectToVisible:(CGRect)rect animated:(BOOL)animated;         // scroll so rect is just visible (nearest edges). nothing if rect completely visible

 

注意:

1. 使用 - (void)setContentOffset:(CGPoint)contentOffset animated:(BOOL)animated 时, 需要注意, 

在uiscrollview的委托中只有, 以下这个方法可以阻止减速, 并且更改内容偏移, 一就是setContentOffset这个方法

- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView;  

 

2. viewForZoomingInScrollView: 需要设置

minimumZoomScale 

maximumZoomScale 才能够调用 

uiscrollview缩放图片至少实现一下两个代理, 但能让缩放过程更加自然

//实现图片在缩放过程中居中
//scrollView正在缩放
- (void)scrollViewDidZoom:(UIScrollView *)scrollView
{
    CGFloat offsetX = (scrollView.bounds.size.width > scrollView.contentSize.width)?(scrollView.bounds.size.width - scrollView.contentSize.width)/2 : 0.0;
    CGFloat offsetY = (scrollView.bounds.size.height > scrollView.contentSize.height)?(scrollView.bounds.size.height - scrollView.contentSize.height)/2 : 0.0;
    UIView *v = [scrollView.subviews objectAtIndex:0];
    v.center = CGPointMake(scrollView.contentSize.width/2 + offsetX,scrollView.contentSize.height/2 + offsetY);
}

#pragma mark - UIScrollViewDelegate

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return _imageView;
}