Question

我在收藏视图中显示了相册图片的数量。对于在单元格方法中显示图像，cellForItemAtIndexPath包含如下代码。

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{

      AlbumImageCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"AlbumImageCell" forIndexPath:indexPath];
      cell.layer.shouldRasterize = YES;
      cell.layer.rasterizationScale = [UIScreen mainScreen].scale;
      if (cell == nil) {
        cell = [[[NSBundle  mainBundle] loadNibNamed:@"AlbumImageCell" owner:self options:nil] objectAtIndex:0];
      }

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *inputPath = [[self.arrTbl_Album_Image objectAtIndex:indexPath.row]objectAtIndex:2 ];

    NSString *imageEx=[inputPath pathExtension];
    NSString *imageName=[[inputPath lastPathComponent]stringByDeletingPathExtension];

    NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@",imageName,imageEx]];

    [cell.albumImage setImage:[UIImage imageWithContentsOfFile:fullPath]];

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
      NSData *data= [NSData dataWithContentsOfFile:fullPath];
      UIImage *theImage=[UIImage imageWithData:data];

    dispatch_async(dispatch_get_main_queue(), ^{
        cell.albumImage.image=theImage;
    });
});
}

问题是当我滚动时UICollection视图滚动工作缓慢，所以我需要使滚动更快。我应用一些解决方案，但仍然没有解决问题。请帮我解决这个问题。

Answer 1

[cell.albumImage setImage:[UIImage imageWithContentsOfFile:fullPath]]; // set image on main thread

＆安培;

cell.albumImage.image=theImage;

两者相同

删除第一行代码

[cell.albumImage setImage：[UIImage imageWithContentsOfFile：FULLPATH]];

Answer 2

NSString *docsDir = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];
 NSString *fullPath = [NSString stringWithFormat:@"%@/%@", docsDir,[filePathsArray objectAtIndex:indexPath.item]];
[cell.albumImage setImage:[UIImage imageWithContentsOfFile:fullPath]];

Answer 3

您已使用[cell.albumImage setImage:[UIImage imageWithContentsOfFile:fullPath]];

设置了图片

他们为什么要使用下面的代码再次设置图像。您需要删除该代码。

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
      NSData *data= [NSData dataWithContentsOfFile:fullPath];
      UIImage *theImage=[UIImage imageWithData:data];

    dispatch_async(dispatch_get_main_queue(), ^{
        cell.albumImage.image=theImage;
    });
});

Answer 4

执行每个滚动

这是一项艰巨的任务

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *inputPath = [[self.arrTbl_Album_Image objectAtIndex:indexPath.row]objectAtIndex:2 ];

NSString *imageEx=[inputPath pathExtension];
NSString *imageName=[[inputPath lastPathComponent]stringByDeletingPathExtension];

NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@",imageName,imageEx]];

你可以避免吗？让我们说，使用xcassets？当然，它会更快。检索图像的后台操作根本不是问题，它位于后台。

已添加：您可以在此处查看如何使用xcassets：https://developer.apple.com/library/ios/documentation/Xcode/Reference/xcode_ref-Asset_Catalog_Format/index.html#//apple_ref/doc/uid/TP40015170-CH18-SW1

Answer 5

我遇到了同样的问题。当我分析应用程序（滚动时）时，我可以看到时间花在了AppleJPEG的某个地方（不记得确切的名字）。我的图像太大而且必须渲染得更小（对于单元格的大小）而且这恰好在主线程上。

尝试在后台线程上渲染图像。查看：https://developer.apple.com/videos/play/wwdc2012-211/

如何使UICollectionView滚动更快

5 个答案: