NSURLConnection下载很长

Question

我在下载5 MB文件时遇到问题，在iPhone 5上使用iOS 6.1需要2分多钟。

使用相同iOS版本的iPhone 4S仅需10秒，两者都使用WiFi。

我尝试了不同的缓存策略和NSURLRequest的超时间隔，它没有改变，它仍然需要很长时间。 下载是通过HTTP。

我正在使用NSURLConnection类，在下载这个“大”文件之前我正在下载另外两个。

不知道还有什么可以重要，减少时间。

提前致谢。

码：

@interface MyClass : NSObject <NSURLConnectionDelegate>
{
  @private id delegate;
  NSURLConnection *connection;
  NSMutableData* responseData;
  //...
}


#import "MyClass.h"

@implementation MyClass

-(void)getObj1:(id)delegateObj
{
   delegate = delegateObj;

   NSString *url = @"...";

   NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url] cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:120.0];

   connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];

   if(connection)
   {
      responseData = [NSMutableData data];
   }
}

-(void)getObj2:(*String)somesString
{

   NSString *url = @"...";

   NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url] cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:120.0];

   connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];

   if(connection)
   {
    responseData = [NSMutableData data];
   }
}

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{ 
    //....
}


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

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
   if(firstRequest)
   {
      //save data from first request and set responseData clear
      [self getObj2:@"..."];
   }
}

和其他没有什么特别的，我希望这就足够了

我发现这篇文章https://devforums.apple.com/message/754875#754875但对我来说仍然无法正常工作。 但是现在我更好地了解这种奇怪的情况。

Answer 1

使用AFDownloadRequestOperation（AFNetworking“sublass”） - 您也可以暂停/恢复操作。

这里有一个示例https://stackoverflow.com/a/12209618

Answer 2

你试过AFNetworking吗？ 它是NSURLConnection包装器。 我不确定它是否能帮助你获得更快的下载速度，但它肯定会让你比NSURLConnection优势。

Answer 3

您使用GCD dispatch_async队列来执行NSURLRequest请求集以从服务器下载数据或获取服务器响应。

NSString *webURL = @"http://therealurl.appspot.com/?format=json&url=bit.ly/a";
NSURL *url = [NSURL URLWithString:webURL];
NSURLRequest *awesomeRequest = [NSURLRequest requestWithURL:url];
NSURLConnection *connection=[[NSURLConnection alloc] initWithRequest:awesomeRequest delegate:self];
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0ul);
dispatch_async(queue, ^{
    NSRunLoop *loop=[NSRunLoop currentRunLoop];
    [connection scheduleInRunLoop:loop forMode:NSRunLoopCommonModes];
    //[self processTheAwesomeness];
});

Answer 4

我建议一个解决方案，你有一种沟通管理器，它有一个它处理的NSOperationQueue ，有一个入口点方法，你给它一个你要下载内容的URL，一个成功和一个失败块。 通信管理器创建一个NSOperation ，您可以在其中创建NSURLRequest并处理回调。

一旦通信管理器将操作放入队列，就会调用其start方法。 在我的通信管理器实现中，我通过NSMutableDictionary跟踪（除了将操作放入队列之外）每个已启动的操作，以便您可以取消单个或所有操作（在提供的示例代码中， operationKey用于此目的。 JSONOperation返回（如果成功）一个NSString到通信器，但它也可以是任何类型的数据，例如我使用相同的类来下载图像，所以我会传回数据对象本身。下面你可以找到我的JSONOperation以类为例。我喜欢我可以将其他文件放在Gist上的想法。

我的NSOperation看起来像这样

@interface JSONOperation : NSOperation <NSURLConnectionDataDelegate, OperationDelegate>  
  + (instancetype)jsonOperationForProvider:(id)provider success:(OperationSuccessWithString)success failure:(OperationFailure)failure;  
@end  

#import "JSONOperation.h"
#import "ProviderDelegate.h"

@interface JSONOperation()
@property (nonatomic, assign) BOOL executing;
@property (nonatomic, assign) BOOL finished;
@property (nonatomic, assign) BOOL cancelled;

@property (nonatomic, strong) NSURL *url;

@property (nonatomic, weak) id <ProviderDelegate> delegate;
@property (nonatomic, strong) NSURLConnection *connection;
@property (nonatomic, strong) NSMutableData *receivedData;

@property (nonatomic, copy) OperationFailure failure;
@property (nonatomic, copy) OperationSuccessWithString success;
@end

@implementation JSONOperation 

- (void)start
{
    if ([self isCancelled])
{
    [self willChangeValueForKey:@"isFinished"];
    _finished = YES;
    [self didChangeValueForKey:@"isFinished"];

    return;
}

    NSURLRequest *request = [NSURLRequest requestWithURL:self.url];
    self.connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO];
    [self.connection scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
    [self.connection start];

    [self willChangeValueForKey:@"isExecuting"];
    _executing = YES;
    [self didChangeValueForKey:@"isExecuting"];
}

- (NSMutableData *)receivedData
{
    if (nil == _receivedData) {
        _receivedData = [NSMutableData data];
    }
    return _receivedData;
}

+ (instancetype)jsonOperationForProvider:(id <ProviderDelegate>)provider success:(OperationSuccessWithString)success failure:(OperationFailure)failure
{
    NSAssert(nil != provider, @"provider parameter can't be nil");

    JSONOperation *operation = [[[self class] alloc] init];
    operation.delegate = provider;
    operation.url = provider.contentURL;
    operation.failure = failure;
    operation.success = success;

    return operation;
}

- (BOOL)isConcurrent {
    return YES;
}

- (BOOL)isExecuting {
    return _executing;
}

- (BOOL)isFinished {
    return _finished;
}

- (BOOL)isCancelled {
    return _cancelled;
}

#pragma mark - NSURLConnectionDataDelegate

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {

    if (_success) {
        NSString *receivedText = [[NSString alloc] initWithData:self.receivedData encoding:NSUTF8StringEncoding];
        _receivedData = nil;

        self.success(self, receivedText);
    }

    [self willChangeValueForKey:@"isFinished"];
    [self willChangeValueForKey:@"isExecuting"];

    _executing = NO;
    _finished = YES;

    [self didChangeValueForKey:@"isExecuting"];
    [self didChangeValueForKey:@"isFinished"];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    [self.receivedData appendData:data];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    [connection cancel];
    _connection = nil;
    _receivedData = nil;
    _url = nil;

    if (_failure) {
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            self.failure(self, error);
    }];
    }

    [self willChangeValueForKey:@"isFinished"];
    [self willChangeValueForKey:@"isExecuting"];

    _executing = NO;
    _finished = YES;

    [self didChangeValueForKey:@"isExecuting"];
    [self didChangeValueForKey:@"isFinished"];
}

#pragma mark - OperationDelegate

- (NSString *)operationKey
{
    return [self.url absoluteString];
}

- (id)provider
{
    return _delegate;
}

- (void)cancelOperation
{
    _failure = nil;
    _success = nil;

    [self.connection cancel];
    _connection = nil;

    _receivedData = nil;
    _url = nil;

    [self willChangeValueForKey:@"isCancelled"];
    [self willChangeValueForKey:@"isFinished"];
    [self willChangeValueForKey:@"isExecuting"];

    _executing = NO;
    _finished  = YES;
    _cancelled = YES;

    [self didChangeValueForKey:@"isCancelled"];
    [self didChangeValueForKey:@"isExecuting"];
    [self didChangeValueForKey:@"isFinished"];
}

@end

编辑 - Gist示例文件

Answer 5

根据我的经验， AFNetworking在处理下载方面做了很棒的工作。我正在对10+ MB大小的文件使用下载操作。所以我强烈建议使用它。

我在堆栈上的回答显示进度 NSUrlconnection 。看看我用AFNetworking和NSUrlconnection实现这两种方式的答案。你可以尝试两种方式并且可以看到进度，你可以计算每个数据包中如何下载字节。通过它跟踪它您可以分析下载时间的变化情况。 试试吧

Answer 6

只需尝试使用gzip压缩NSURLRequest的远程文件。 它会大大加快您的连接速度。

要使用它，你需要在服务器上安装它，好消息是如果你在服务器上使用apache2 ，它默认是。 要测试以确保您的服务器/ URL启用了gzip压缩，请使用以下在线工具进行测试： http ： //www.feedthebot.com/tools/gzip/

如果答案是肯定的，请继续将代码添加到Xcode中的Objective-C代码中。 在您的代码中的这一行之后：

NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url] cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:120.0];

只需添加：

// Create a mutable copy of the immutable request and add more headers
NSMutableURLRequest *mutableRequest = [request mutableCopy];

//add gzip compression
[mutableRequest addValue:@"gzip" forHTTPHeaderField:@"Accept-Encoding"];

// Now set our request variable with an (immutable) copy of the altered request
request = [mutableRequest copy];

这将显着加快您的响应时间，并且您不需要将AFNetworking用于小型NSURLRequest或NSURLConnection任务。

Answer 7

我不确定你的问题是什么，但以下代码对我来说可靠。

- (id)init
{
  self.downloadQueue = [[NSOperationQueue alloc] init];
  [self.downloadQueue setMaxConcurrentOperationCount:1];
}

- (void)doDownload:(NSURL *)url
{
  [self.downloadQueue addOperation:[NSBlockOperation blockOperationWithBlock:^{

    NSData *data =[NSData dataWithContentsOfURL:url];

    dispatch_sync(dispatch_get_main_queue(), ^{
      NSAutoreleasePool *mainQueuePool = [[NSAutoreleasePool alloc] init];

      ... update user interface ...

      [mainQueuePool release];
    });

  }]];
}

Answer 8

我认为这是你设备中的一个问题。 尝试朋友的其他设备。