Iphone ALAssetLibrary和iOS 5.0

我编写了从资产库中获取数据的简单方法，该方法在iOS4.3上运行良好，但在iOS5中获取图像时会出现延迟。我应该如何加快iOS 5上的抓取过程

-(void)setImages
{
    int count =0;
    int photoNumber = [[templateDictionary objectForKey:@"ElementsOnPage"] intValue]; 
    for (int i=currentCount; count<photoNumber; i++) {
       [self data:count+1 count:i];
        count++;
    }
 }


-(void)data:(int)photoNumber count:(int)currentCount 
{  
NSURL *url;
UIImageView *firstImageView = [[UIImageView alloc]init];
CGFloat x,y,wid,h;
float ang;
 if (currentCount>=[ImageURLArray count]) {
    [firstImageView release];
    return;
}
else
{
    url = [NSURL URLWithString:[ImageURLArray objectAtIndex:currentCount]];
    switch (photoNumber) {
        case 1:
        {

            x = [[templateDictionary  objectForKey:@"FirstElement_X"]floatValue];
            y=[[templateDictionary objectForKey:@"FirstElement_Y"]floatValue];
            wid = [[templateDictionary objectForKey:@"FirstElement_Width"]floatValue];
            h=[[templateDictionary objectForKey:@"FirstElement_Height"]floatValue];
            ang =[[templateDictionary objectForKey:@"FirstElement_Angle"]floatValue];
            firstImageView.tag = 1+10;
            //FirstImage

        }
            break;
        case 2:
        {
            x = [[templateDictionary objectForKey:@"SecondElement_X"]floatValue];
            y=[[templateDictionary objectForKey:@"SecondElement_Y"]floatValue];
            wid = [[templateDictionary objectForKey:@"SecondElement_Width"]floatValue];
            h=[[templateDictionary objectForKey:@"SecondElement_Height"]floatValue];
            ang =[[templateDictionary objectForKey:@"SecondElement_Angle"]floatValue];
            firstImageView.tag=2+10;
            //SecondImage

        }
            break;
        case 3:
        {
            x = [[templateDictionary objectForKey:@"ThirdElement_X"]floatValue];
            y=[[templateDictionary objectForKey:@"ThirdElement_Y"]floatValue];
            wid = [[templateDictionary objectForKey:@"ThirdElement_Width"]floatValue];
            h=[[templateDictionary objectForKey:@"ThirdElement_Height"]floatValue];
            ang =[[templateDictionary objectForKey:@"ThirdElement_Angle"]floatValue];
            firstImageView.tag = 3+10;
            //ThirdImage
        }
            break;
        default:
            break;
    }
    [firstImageView setFrame:CGRectMake(x, y, wid, h)];

    dispatch_async(dispatch_get_main_queue(), ^
                   {
                       NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
                       ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
                       // Enumerate just the photos and videos group by using ALAssetsGroupSavedPhotos.

                       [library assetForURL:url 

                                resultBlock:^(ALAsset* asset) 
                        {

                            UIImage* img = [UIImage imageWithCGImage:[asset.defaultRepresentation fullResolutionImage]];
                            [firstImageView setImage:img];

                        }  
                               failureBlock:^(NSError* error) 
                        {
                            NSLog(@"error requesting asset");
                        }
                        ];

                       [library release];   

                       // Group enumerator Block
                       [pool release];
                   });


    if ([[contentType objectAtIndex:currentCount]isEqualToString:@"1"]) {
        UIButton *videoImage = [[UIButton alloc]initWithFrame:CGRectMake((firstImageView.frame.size.width/2)-25,(firstImageView.frame.size.height/2)-25,50,50)];
        videoImage.transform = CGAffineTransformMakeRotation(ang*(3.14/180));
        [videoImage setBackgroundImage:[UIImage imageNamed:@"videothumb.png"] forState:UIControlStateNormal];
        [videoImage addTarget:self action:@selector(PlayMusicOnClickofButton:) forControlEvents:UIControlEventTouchUpInside];
        [firstImageView addSubview:videoImage];
        videoImage.tag  = currentCount+1000;
        [videoImage release];
    }
}
firstImageView.transform = CGAffineTransformMakeRotation(ang*(3.14/180));
firstImageView.userInteractionEnabled = YES;
[coverImageView addSubview:firstImageView];
[coverImageView setImage:[UIImage imageNamed:innerBackground]];

[firstImageView release];

-（无效）设置图像
{
整数计数=0；
int photoNumber=[[templateDictionary objectForKey:@“ElementsOnPage”]intValue]；
对于（int i=currentCount；count=[ImageURLArray count]）{
[firstImageView发布]；
返回；
}
其他的
{
url=[NSURL URLWithString:[ImageURLArray objectAtIndex:currentCount]]；
开关（照片编号）{
案例1：
{
x=[[templateDictionary objectForKey:@“FirstElement_x”]floatValue]；
y=[[templateDictionary objectForKey:@“FirstElement_y”]floatValue]；
wid=[[templateDictionary objectForKey:@“FirstElement_Width”]floatValue]；
h=[[templateDictionary objectForKey:@“FirstElement_Height”]floatValue]；
ang=[[templateDictionary objectForKey:@“FirstElement_Angle”]floatValue]；
firstImageView.tag=1+10；
//第一映像
}
打破
案例2：
{
x=[[templateDictionary objectForKey:@“SecondElement_x”]floatValue]；
y=[[templateDictionary objectForKey:@“SecondElement_y”]floatValue]；
wid=[[templateDictionary objectForKey:@“SecondElement_Width”]floatValue]；
h=[[templateDictionary objectForKey:@“SecondElement_Height”]floatValue]；
ang=[[templateDictionary objectForKey:@“SecondElement_Angle”]floatValue]；
firstImageView.tag=2+10；
//第二映像
}
打破
案例3：
{
x=[[templateDictionary objectForKey:@“ThirdElement_x”]floatValue]；
y=[[templateDictionary objectForKey:@“ThirdElement_y”]floatValue]；
wid=[[templateDictionary objectForKey:@“ThirdElement_Width”]floatValue]；
h=[[templateDictionary objectForKey:@“ThirdElement_Height”]floatValue]；
ang=[[templateDictionary objectForKey:@“第三个数据元素角度”]floatValue]；
firstImageView.tag=3+10；
//三十岁
}
打破
违约：
打破
}
[firstImageView设置帧：CGRectMake（x，y，wid，h）]；
dispatch\u async（dispatch\u get\u main\u queue（）^
{
NSAutoreleasePool*池=[[NSAutoreleasePool alloc]init]；
AlassetLibrary*library=[[AlassetLibrary alloc]init]；
//使用AlassetGroupSavedPhotos仅枚举照片和视频组。
[library assetForURL:url
结果块：^（ALAsset*资产）
{
UIImage*img=[UIImage imageWithCGImage:[asset.defaultRepresentation fullResolutionImage]]；
[firstImageView设置图像：img]；
}  
故障块：^（N错误*错误）
{
NSLog（@“请求资产时出错”）；
}
];
[图书馆发行]；
//组枚举器块
[池释放]；
});
如果（[[contentType objectAtIndex:currentCount]isEqualToString:@“1”]）{
UIButton*videoImage=[[UIButton alloc]initWithFrame:CGRectMake（（firstImageView.frame.size.width/2）-25，（firstImageView.frame.size.height/2）-25,50,50）]；
videoImage.transform=CGAffineTransformMakeRotation（ang*（3.14/180））；
[videoImage setBackgroundImage:[UIImage ImageName:@“videothumb.png”]用于状态：UIControlStateNormal]；
[videoImage addTarget:self action:@selector（播放音乐单击按钮：）for ControlEvents:UIControlEventTouchUpInside]；
[firstImageView添加子视图：视频图像]；
videoImage.tag=当前计数+1000；
[影像发布]；
}
}
firstImageView.transform=CGAffineTransformMakeRotation（ang*（3.14/180））；
firstImageView.userInteractionEnabled=是；
[coverImageView添加子视图：firstImageView]；
[coverImageView setImage:[UIImage ImageName:innerBackground]]；
[firstImageView发布]；

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}

我已经向苹果公司报告了一个关于iOS5中assetForUrl性能下降的bug（在开发论坛上苹果公司的一名员工提出请求后）

背景：assetLibrary经过重构，现在基于CoreData，在每次assetForUrl调用时，SDK实际上会打开一个新的SQLite连接（BAH…），从而导致显著的性能损失

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临时解决方案：在我的应用程序中，我需要使用assetForUrl加载200张图片。在IOS4中需要100毫秒，在iOS5中大约需要5秒以上。我发现枚举整个库（大约1500张图片）并将其缓存在URL-->资产字典中大约需要3秒钟。我现在正在使用这种技术。如果您持有过时的资产并对库进行更改，请小心它们。

+1表示保留。你知道答案了吗？不，我没有解决延迟的办法。内存没有问题吗？此解决方案似乎不可扩展。