ios – 使用AFNetworking加载图像的UICollectionView滚动性能

概述我已经阅读了很多关于糟糕滚动的UICollectionView帖子,但似乎都没有直接应用,或者它们仍然没有答案. 我正在使用AFNetworking将图像(95px平方)异步加载到每个单元格上,然后当图像再次滚动到视图中时,图像从缓存中恢复(由响应代码验证为0而不是200). 这是我尝试过的： >注释掉weakCell.photoView.image = image;因此图像不会在屏幕上绘制,滚动 我已经阅读了很多关于糟糕滚动的UICollectionVIEw帖子,但似乎都没有直接应用,或者它们仍然没有答案.

我正在使用AFNetworking将图像(95px平方)异步加载到每个单元格上,然后当图像再次滚动到视图中时,图像从缓存中恢复(由响应代码验证为0而不是200).

这是我尝试过的：

>注释掉weakCell.photoVIEw.image = image;因此图像不会在屏幕上绘制,滚动更平滑(在http获取期间仍然有点结果)
>从cellForRowAtIndexPath方法中删除了所有AFNetworking代码,滚动更加平滑(即使屏幕上仍然绘制了自定义单元格阴影等)
>当我在屏幕上仅绘制单元格视图(带阴影)时,100个单元格的滚动非常平滑.一旦我开始在屏幕上绘制图像,我的设备上的滚动效果非常差,甚至在模拟器上也很明显. Instagram在个人资料视图中可以非常流畅地滚动数百个单元格,因此我正试图接近他们的表现.

我有什么方法可以改进下面的任何代码,以提高滚动性能？

这是我的手机代码：

#import "PhotogalleryCell.h"@implementation PhotogalleryCell- (ID)initWithFrame:(CGRect)frame{    self = [super initWithFrame:frame];    if (self)    {        // Setup the background color,shadow,and border        self.backgroundcolor = [UIcolor colorWithWhite:0.25f Alpha:1.0f];        self.layer.bordercolor = [UIcolor blackcolor].CGcolor;        self.layer.borderWIDth = 0.5f;        self.layer.shadowcolor = [UIcolor blackcolor].CGcolor;        self.layer.shadowRadius = 3.0f;        self.layer.shadowOffset = CGSizeMake(0.0f,2.0f);        self.layer.shadowOpacity = 0.5f;        // Make sure we rasterize for retina        self.layer.rasterizationScale = [UIScreen mainScreen].scale;        self.layer.shouldRasterize = YES;        // Add to the content vIEw        self.photoVIEw = [[UIImageVIEw alloc] initWithFrame:self.bounds];        [self.contentVIEw addSubvIEw:self.photoVIEw];    }    return self;}- (voID)prepareForReuse{    [super prepareForReuse];    self.photoVIEw.image = nil;    self.largeImageURL = nil;}

这是我的UICollectionVIEw代码：

#pragma mark - Collection VIEw Delegates- (NSInteger)numberOfSectionsInCollectionVIEw:(UICollectionVIEw *)collectionVIEw{    return 1;}- (NSInteger)collectionVIEw:(UICollectionVIEw *)collectionVIEw numberOfItemsInSection:(NSInteger)section{    return [zePhotos count];}- (UICollectionVIEwCell *)collectionVIEw:(UICollectionVIEw *)collectionVIEw cellForItemAtIndexPath:(NSIndexPath *)indexPath{    PhotogalleryCell *cell = [collectionVIEw dequeueReusableCellWithReuseIDentifIEr:kPGPhotoCellIDentifIEr forIndexPath:indexPath];    // Get a reference to the image dictionary    NSDictionary *photoDict = [[zePhotos objectAtIndex:indexPath.row] objectForKey:@"image"];    // Asynchronously set the thumbnail vIEw    __weak PhotogalleryCell *weakCell = cell;    Nsstring *thumbnailURL = [[photoDict objectForKey:@"thumbnail"] objectForKey:@"url"];    NSURLRequest *photoRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:thumbnailURL]];    [cell.photoVIEw setimageWithURLRequest:photoRequest                          placeholderImage:nil                                   success:^(NSURLRequest *request,NShttpURLResponse *response,UIImage *image) {                                       weakCell.photoVIEw.image = image;                                   }                                   failure:^(NSURLRequest *request,NSError *error) {                                       NSLog(@"Error retrIEving thumbnail... %@",[error localizedDescription]);                                   }];    // Cache the large image URL in case they tap on this cell later    cell.largeImageURL = [[photoDict objectForKey:@"large"] objectForKey:@"url"];    return cell;}- (voID)collectionVIEw:(UICollectionVIEw *)collectionVIEw dIDSelectItemAtIndexPath:(NSIndexPath *)indexPath{    [self performSegueWithIDentifIEr:@"showPhotoDetail" sender:self];}

解决方法 您可以尝试将shadowPath添加到您的单元初始化,它应该提高性能,这是我在我的一个项目中使用的代码添加一个舍入的shadowPath(有关更多选择,请参阅UIBezIErPath方法)

self.layer.shadowPath = [UIBezIErPath bezIErPathWithRoundedRect:self.frame.bounds                                              byRoundingCorners:UIRectCornerAllCorners                                                    cornerRadii:CGSizeMake(10,10)].CGPath;

此外,如果我没记错AFNetworking没有调整从服务器返回的图像的大小,所以它可能会影响你的图像质量(尽管你添加到UIImageVIEw的缩放方法),我建议调度返回的图像来调整它的大小如果你想这样：

CGSize targetSize = cell.photoVIEw.bounds.size;[cell.photoVIEw setimageWithURLRequest:photoRequest                      placeholderImage:nil                               success:^(NSURLRequest *request,UIImage *image) {                                    dispatch_async(dispatch_get_global_queue(disPATCH_QUEUE_PRIORITY_DEFAulT,0),^{                                       CGfloat imageHeight = image.size.height;                                       CGfloat imageWIDth = image.size.wIDth;                                       CGSize newSize = weakCell.imageVIEw.bounds.size;                                       CGfloat scaleFactor = targetSize.wIDth / imageWIDth;                                       newSize.height = imageHeight * scaleFactor;                                       UIGraphicsBeginImageContextWithOptions(newSize,NO,0.0);                                       [image drawInRect:CGRectMake(0,newSize.wIDth,newSize.height)];                                       UIImage *small = UIGraphicsGetimageFromCurrentimageContext();                                       UIGraphicsEndImageContext();                                       dispatch_async(dispatch_get_main_queue(),^{                                           weakCell.photoVIEw.image = small;                                       });                                   });                               }                               failure:^(NSURLRequest *request,NSError *error) {                                   NSLog(@"Error retrIEving thumbnail... %@",[error localizedDescription]);                               }];

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