UIScrollView + UIImage和縮放：不流暢

我有視圖控制器，裏面，我有一個UIScrollView，管理縮放，和UIImage。現在我正在使用UIScrollViewDelegate代表和方法viewForZoomingInScrollView:處理縮放效果......但結果非常差，絕對不是流暢的！UIScrollView + UIImage和縮放：不流暢

這是我的代碼：

#import "ImageViewController.h" 

@interface ImageViewController() <UIScrollViewDelegate, UIActionSheetDelegate> 
@property (strong, nonatomic) IBOutlet UIScrollView *scrollView; 
@property (weak, nonatomic) IBOutlet UIImageView *imageView; 

@end 

@implementation ImageViewController 

- (void)viewDidLoad { 
    [super viewDidLoad]; 

    self.scrollView.delegate = self; 
    self.scrollView.maximumZoomScale = 3.0; 

    // some code 
} 

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView { 
    return self.imageView; 
} 
// last update 
- (void)scrollViewDidZoom:(UIScrollView *)scrollView { 
    if ([self.scrollView zoomScale] < 1.0) { 
     [self.scrollView setZoomScale:1.0]; 
    } 
} 

// some other methods... 

@end

這是故事板視圖：