Question

我正在开发一个用户可以共享图像的应用程序。使用php文件我在服务器上传文件并使用php文件下载。当我下载文件时需要很长时间。我怎么做得有点快

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
NSString *data1 = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
NSArray *arrImg = [data1 componentsSeparatedByString:@"@@@"];
    int i;
    NSMutableArray *receivedUrlArr = [[NSMutableArray alloc]init];
    NSString *str,*strNew,*path;
    NSData *imageData;
    ImagesClass *obj;
    int count;
    for ( i=0; i<[arrImg count]-1; i++) {
        [receivedUrlArr addObject:[arrImg objectAtIndex:i]];

        str = [NSString stringWithFormat:@"http:////receive_images/%@",[receivedUrlArr objectAtIndex:i]];
        strNew = [str stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
        UIImage *myImage = [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:strNew]]];  
        obj = [[ImagesClass alloc]init];
        obj.imageId = i+1;
        obj.imageName = [[arrImg objectAtIndex:i] stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
        obj.thumbImage = myImage;

        [[DBModel database]inserttoReceivedList:obj receiverMobNo:mobileno];

        path = [RECEIVEDIMAGE_DIR stringByAppendingPathComponent:[NSString stringWithFormat:@"%@",obj.imageName]];
        imageData = UIImagePNGRepresentation(obj.thumbImage);
        [imageData writeToFile:path atomically:YES];
    }
}

提前致谢。

Answer 1

无论您的图像存储方法有多高效，您都会受到连接速度的瓶颈。

但是，你似乎错误地采取了这种做法。 -connection：didReceiveData用于递增地接收数据。您似乎假设一旦收到数据，您已完成加载图像，然后执行一些复杂的处理以保存部分下载的图像。相反，NSURLConnection的委托应该实现-connectionDidFinishLoading。在此方法中，您将连接的数据转换为图像并保存。

以下是我如何设置的方法：假设您有一个显示图像/需要下载更多图像的控制器类。现在，创建一个名为“ImageDownloader”的类，它实现了NSURLConnection Delegate。初始化此类时，您将为其提供图像名称和需要下载的图像的URL。在ImageDownloader中，您将需要一个NSMutableData属性。最后，您需要一个诸如-startDownload之类的方法来使事情发生变化。

-startDownload应首先确保您的NSMutableData属性为空并初始化。完成后，您可以开始NSURLConnection的下载。务必将委托设置为ImageDownloader的实例。 In -connection：didReceiveData，将接收到的数据附加到NSMutableData属性。 In -connectionDidFinishLoading，将该NSMutableData属性转换为图像，并使用控制器提供的图像名称进行保存。从那里，让控制器实例知道通过委托方法调用或通知保存图像。

希望这有帮助。

编辑：IIRC，Apple提供了一些名为“ImageDownloader”的示例代码，如果这个解释令人困惑，这个代码非常相似。

Answer 2

我开发了一个名为File Downloader的类，如下所示：

步骤1：创建一个“FileDownloader.h”并将其添加到其中。

#import <Foundation/Foundation.h>

@protocol fileDownloaderDelegate <NSObject>

@optional
- (void)downloadProgres:(NSNumber*)percent forObject:(id)object;

@required

- (void)downloadingStarted;
- (void)downloadingFinishedFor:(NSURL *)url andData:(NSData *)data;
- (void)downloadingFailed:(NSURL *)url;

@end

@interface FileDownloader : NSObject
{

@private
    NSMutableURLRequest *_request;
    NSMutableData *downloadedData;
    NSURL *fileUrl;

    id <fileDownloaderDelegate> delegate;

    double totalFileSize;
}

@property (nonatomic, strong) NSMutableURLRequest *_request;
@property (nonatomic, strong) NSMutableData *downloadedData;
@property (nonatomic, strong) NSURL *fileUrl;

@property (nonatomic, strong) id <fileDownloaderDelegate> delegate;

- (void)downloadFromURL:(NSString *)urlString;

@end

步骤2：创建“FileDownloader.m”并编写以下内容

#import "FileDownloader.h"

@implementation FileDownloader

@synthesize _request, downloadedData, fileUrl;
@synthesize delegate;

- (void)downloadFromURL:(NSString *)urlString
{
    [self setFileUrl:[NSURL URLWithString:[urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]];

    self._request = [NSMutableURLRequest requestWithURL:self.fileUrl cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:60.0f];
    NSURLConnection *cn = [NSURLConnection connectionWithRequest:self._request delegate:self];
    [cn start];
}


#pragma mark - NSURLConnection Delegate
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    if([delegate respondsToSelector:@selector(downloadingStarted)])
    {
        [delegate performSelector:@selector(downloadingStarted)];
    }

    totalFileSize = [response expectedContentLength];    
    downloadedData = [NSMutableData dataWithCapacity:0];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [downloadedData appendData:data];

    if([delegate respondsToSelector:@selector(downloadProgres:forObject:)])
    {
        [delegate performSelector:@selector(downloadProgres:forObject:) withObject:[NSNumber numberWithFloat:([downloadedData length]/totalFileSize)] withObject:self];
    }
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    if([delegate respondsToSelector:@selector(downloadingFailed:)])
    {
        [delegate performSelector:@selector(downloadingFailed:) withObject:self.fileUrl];
    }    
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    if([delegate respondsToSelector:@selector(downloadingFinishedFor:andData:)])
    {
        [delegate performSelector:@selector(downloadingFinishedFor:andData:) withObject:self.fileUrl withObject:self.downloadedData];
    }
}


@end

步骤3：现在在viewcontroller中导入“#import”FileDownloader.h“”并在.h文件中导入“fileDownloaderDelegate”代理

步骤4：创建对象，设置代理和URL以下载文件。

FileDownloader *objDownloader = [[FileDownloader alloc] init];
[objDownloader setDelegate:self];
[objDownloader downloadFromURL:@"yourURL"];

步骤5：不要忘记在视图控制器中实现Delegate方法以获取有关下载进度的通知。享受..

通过didReceivedata导入图像

2 个答案: