Iphone 如何改进图像加载问题。有没有类似缓存的解决方案

我使用Parse.com构建了一个iOS应用程序

在我的应用程序中，我显示了许多来自网络的数据

为了快速加载数据，我使用了cache

kpfcachepolicycachetennetwork

。它可以很好地加载数据，但在滚动图像时需要花费一些时间来加载。

首先加载白色图像，然后加载图像

有没有像缓存这样的解决方案可以在ImageView中显示图像而不中断。

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谢谢。

这是在后台加载图像的代码。选中此项

以下是在后台加载图像的代码。选中此复选框，您可以使用它来执行此操作

也可以用于缓存目的。

您可以使用

您还可以用于缓存目的。

是的，您可以使用UIImageview类别并进行排序

如果编辑现有图像，然后通过操纵其URL从同一URL加载，则还可以禁用通常需要的特定图像的缓存

-(void)setImageWithURL:(NSURL *)url
       placeholderImage:(UIImage *)placeholderImage

如本文所述

另一个选项可以是刷新缓存的工具。

是的，您可以使用UIImageview类别并对其进行排序

如果编辑现有图像，然后通过操纵其URL从同一URL加载，则还可以禁用通常需要的特定图像的缓存

-(void)setImageWithURL:(NSURL *)url
       placeholderImage:(UIImage *)placeholderImage

如本文所述

---

另一个选项是使用刷新缓存的工具。

我在gcd的帮助下编写代码，您只需传递imageView的对象和url，它管理所有事情，比如缓存

-(void)downloadingServerImageFromUrl:(UIImageView*)imgView AndUrl:(NSString*)strUrl{


strUrl = [strUrl encodeUrl];

NSString* theFileName = [NSString stringWithFormat:@"%@.png",[[strUrl lastPathComponent] stringByDeletingPathExtension]];


NSFileManager *fileManager =[NSFileManager defaultManager];

NSString *fileName = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"tmp/%@",theFileName]];



imgView.backgroundColor = [UIColor darkGrayColor];
UIActivityIndicatorView *actView = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
[imgView addSubview:actView];
[actView startAnimating];

CGSize boundsSize = imgView.bounds.size;
CGRect frameToCenter = actView.frame;
// center horizontally
if (frameToCenter.size.width < boundsSize.width)
frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2;
else
frameToCenter.origin.x = 0;




 // center vertically
if (frameToCenter.size.height < boundsSize.height)
frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2;
else
frameToCenter.origin.y = 0;

actView.frame = frameToCenter;



dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(queue, ^{

NSData *dataFromFile = nil;
NSData *dataFromUrl = nil;

dataFromFile = [fileManager contentsAtPath:fileName];
if(dataFromFile==nil){
    dataFromUrl=[[[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:strUrl]] autorelease];                      
}

dispatch_sync(dispatch_get_main_queue(), ^{

    if(dataFromFile!=nil){
        imgView.image = [UIImage imageWithData:dataFromFile];
    }else if(dataFromUrl!=nil){
        imgView.image = [UIImage imageWithData:dataFromUrl];  
        NSString *fileName = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"tmp/%@",theFileName]];

        BOOL filecreationSuccess = [fileManager createFileAtPath:fileName contents:dataFromUrl attributes:nil];       
        if(filecreationSuccess == NO){
            NSLog(@"Failed to create the html file");
        }

    }else{
        imgView.image = [UIImage imageNamed:@"NO_Image.png"];  
    }
    [actView removeFromSuperview];
    [actView release];
    [imgView setBackgroundColor:[UIColor clearColor]];
});
});

-（void）下载ServerImageFromURL:（UIImageView*）imgView和URL:（NSString*）strUrl{
strUrl=[strUrl encodeUrl]；
NSString*theFileName=[NSString stringWithFormat:@“%@.png”，[[strUrl lastPathComponent]stringByDeletingPathExtension]；
NSFileManager*fileManager=[NSFileManager defaultManager]；
NSString*文件名=[NSHomeDirectory（）stringByAppendingPathComponent:[NSString stringWithFormat:@“tmp/%@”，文件名]]；
imgView.backgroundColor=[UIColor darkGrayColor]；
UIActivityIndicatorView*actView=[[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite]；
[imgView添加子视图：actView]；
[actView startAnimating]；
CGSize boundsSize=imgView.bounds.size；
CGRect frameToCenter=actView.frame；
//水平居中
if（frameToCenter.size.width

---

}

我在gcd的帮助下编写代码，您只需传递imageView的对象和url，它管理所有的事情，比如缓存

-(void)downloadingServerImageFromUrl:(UIImageView*)imgView AndUrl:(NSString*)strUrl{


strUrl = [strUrl encodeUrl];

NSString* theFileName = [NSString stringWithFormat:@"%@.png",[[strUrl lastPathComponent] stringByDeletingPathExtension]];


NSFileManager *fileManager =[NSFileManager defaultManager];

NSString *fileName = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"tmp/%@",theFileName]];



imgView.backgroundColor = [UIColor darkGrayColor];
UIActivityIndicatorView *actView = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
[imgView addSubview:actView];
[actView startAnimating];

CGSize boundsSize = imgView.bounds.size;
CGRect frameToCenter = actView.frame;
// center horizontally
if (frameToCenter.size.width < boundsSize.width)
frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2;
else
frameToCenter.origin.x = 0;




 // center vertically
if (frameToCenter.size.height < boundsSize.height)
frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2;
else
frameToCenter.origin.y = 0;

actView.frame = frameToCenter;



dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(queue, ^{

NSData *dataFromFile = nil;
NSData *dataFromUrl = nil;

dataFromFile = [fileManager contentsAtPath:fileName];
if(dataFromFile==nil){
    dataFromUrl=[[[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:strUrl]] autorelease];                      
}

dispatch_sync(dispatch_get_main_queue(), ^{

    if(dataFromFile!=nil){
        imgView.image = [UIImage imageWithData:dataFromFile];
    }else if(dataFromUrl!=nil){
        imgView.image = [UIImage imageWithData:dataFromUrl];  
        NSString *fileName = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"tmp/%@",theFileName]];

        BOOL filecreationSuccess = [fileManager createFileAtPath:fileName contents:dataFromUrl attributes:nil];       
        if(filecreationSuccess == NO){
            NSLog(@"Failed to create the html file");
        }

    }else{
        imgView.image = [UIImage imageNamed:@"NO_Image.png"];  
    }
    [actView removeFromSuperview];
    [actView release];
    [imgView setBackgroundColor:[UIColor clearColor]];
});
});

-（void）下载ServerImageFromURL:（UIImageView*）imgView和URL:（NSString*）strUrl{
strUrl=[strUrl encodeUrl]；
NSString*theFileName=[NSString stringWithFormat:@“%@.png”，[[strUrl lastPathComponent]stringByDeletingPathExtension]；
NSFileManager*fileManager=[NSFileManager defaultManager]；
NSString*文件名=[NSHomeDirectory（）stringByAppendingPathComponent:[NSString stringWithFormat:@“tmp/%@”，文件名]]；
imgView.backgroundColor=[UIColor darkGrayColor]；
UIActivityIndicatorView*actView=[[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite]；
[imgView添加子视图：actView]；
[actView startAnimating]；
CGSize boundsSize=imgView.bounds.size；
CGRect frameToCenter=actView.frame；
//水平居中
if（frameToCenter.size.width