UICollectionView滚动很慢

Question

我刚刚创建了一个UICollectionView用户可以将手机中的图像添加到应用程序中的相册功能中.我将图像保存到文档目录中的子目录中,因此可以添加和删除更多图像.但是,当我在集合视图中向上和向下滚动时,它非常迟钝.

如何使滚动变得美观和流畅？

我的代码:前16个图像是预设图像,之后的所有内容都来自文档目录中的子目录

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    CollectionCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Custom" forIndexPath:indexPath];
    //Current index number
    int index=indexPath.section * noOfSection + indexPath.row;
    //Check if its the preset photos
    if(index<16){
        NSString *name=[recipePhotos objectAtIndex:indexPath.section * noOfSection + indexPath.row];
        cell.imageView.image=[UIImage imageNamed:name];
    }

//not preset photos, so retrieve the photos the user added
    else {
        NSData *data= [NSData dataWithContentsOfFile:[recipePhotos objectAtIndex:index]];
        UIImage *theImage=[UIImage imageWithData:data];

        cell.imageView.image=theImage;
        data=nil;
    }

    return cell;
}

Time Profiler给了我这个

Running Time    Self        Symbol Name
568.0ms   63.1% 0.0     Main Thread  0x4048
320.0ms   35.5% 0.0     _pthread_start  0x405e
320.0ms   35.5% 0.0      thread_start
320.0ms   35.5% 0.0       _pthread_start
320.0ms   35.5% 0.0        0x1084be960
310.0ms   34.4% 1.0         0x1084be6f0
7.0ms    0.7%   0.0         mach_msg
2.0ms    0.2%   2.0         objc_msgSend
1.0ms    0.1%   1.0         -[NSAutoreleasePool release]
4.0ms    0.4%   0.0     _dispatch_mgr_thread  0x4052
4.0ms    0.4%   0.0      _dispatch_mgr_thread
4.0ms    0.4%   0.0       _dispatch_mgr_invoke
4.0ms    0.4%   4.0        kevent
3.0ms    0.3%   0.0     _dispatch_worker_thread2  0x62b24
3.0ms    0.3%   1.0      start_wqthread
3.0ms    0.3%   0.0     _dispatch_worker_thread2  0x62a84
3.0ms    0.3%   0.0      start_wqthread
3.0ms    0.3%   0.0       _pthread_wqthread
3.0ms    0.3%   0.0        _dispatch_worker_thread2
3.0ms    0.3%   0.0         _dispatch_queue_invoke
3.0ms    0.3%   0.0          _dispatch_queue_drain
3.0ms    0.3%   0.0           _dispatch_client_callout
2.0ms    0.2%   0.0            my_io_execute_passive_block
1.0ms    0.1%   0.0             __86-[NSPersistentUIManager writePublicPlistWithOpenWindowIDs:optionallyWaitingUntilDone:]_block_invoke_0835
1.0ms    0.1%   0.0              -[NSPersistentUIManager writePublicPlistData:]
1.0ms    0.1%   0.0               -[NSURL(NSURLPathUtilities) URLByAppendingPathComponent:]
1.0ms    0.1%   0.0                -[NSURL getResourceValue:forKey:error:]
1.0ms    0.1%   0.0                 CFURLCopyResourcePropertyForKey
1.0ms    0.1%   0.0             __block_global_2
1.0ms    0.1%   0.0              -[NSPersistentUIManager writeRecords:withWindowInfos:flushingStaleData:]
1.0ms    0.1%   0.0            _dispatch_call_block_and_release
1.0ms    0.1%   0.0             0x1084b8580
1.0ms    0.1%   0.0              mach_msg_send
1.0ms    0.1%   0.0               mach_msg
1.0ms    0.1%   1.0                mach_msg_trap
1.0ms    0.1%   0.0     _pthread_struct_init  0x62a83
1.0ms    0.1%   0.0      start_wqthread
1.0ms    0.1%   0.0       _pthread_wqthread
1.0ms    0.1%   1.0        _pthread_struct_init
1.0ms    0.1%   0.0     start_wqthread  0x62a7f

Answer 1

经过一番折腾后，我发现问题出在几个因素上。

一-缩略图的图像太大，所以我所做的是制作一个单独的图像数组，其图像尺寸较小，适合单元格。二-在@ggrana的帮助下，打开一个单独的线程加快了进程并减少了延迟。三 - 我还发现拥有图像数组而不是图像位置更快 - 唯一的问题是它占用更多内存。