UIScrollView 實現完美縮放

UIScrollView實現縮放非常簡單。
1、首先添加代理UIScrollViewDelegate，並且設置自己創建的UIScrollView對象的代理scrollView.delegate = self;;

2、定義縮放的最大比例和最小比例;
比如：

#define minScale  1
#define maxScale  2


[_scrollView setMinimumZoomScale:minScale];
[_scrollView setMaximumZoomScale:maxScale];
[_scrollView setZoomScale:minScale animated:YES];

3、實現代理方法

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return scrollVew中要縮放的視圖;   
}


// called before the scroll view begins zooming its content縮放開始的時候調用
- (void)scrollViewWillBeginZooming:(UIScrollView *)scrollView withView:(nullable UIView *)view NS_AVAILABLE_IOS(3_2){
    NSLog(@"%s",__func__);
}

// scale between minimum and maximum. called after any 'bounce' animations縮放完畢的時候調用。
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale

{
    //把當前的縮放比例設進ZoomScale，以便下次縮放時實在現有的比例的基礎上
    NSLog(@"scale is %f",scale);
    [_scrollView setZoomScale:scale animated:NO];
}

// 縮放時調用
- (void)scrollViewDidZoom:(UIScrollView *)scrollView{
    // 可以實時監測縮放比例
    NSLog(@"......scale is %f",scrollView.zoomScale);

}