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有人知道如何从主线程停止后台线程的运行循环吗？

我有一个类，它具有从服务器下载文件的功能。从主线程我在后台线程中调用函数 sendHttpRequest 从服务器下载文件。

[self performSelectorInBackground:@selector(sendHttpRequest:) withObject:file];

我用过 CFRunLoopRun(); 使用 CFRunLoopStop(CFRunLoopGetCurrent()) 接收回调并避免退出线程和停止运行循环；下载完成后。

但是我需要在下载数据时停止下载，我怎样才能停止运行循环？

任何帮助....

这是我的代码：

#import "HTTPHandler.h"

@implementation HTTPHandler

@synthesize fileName;

NSURLConnection *urlConnection;
NSMutableData *receivedData;
NSInteger receivedStatusCode;

- (id)initHttpHandler
{
    self = [super init];
    httpEvent = nil;
    return self;
}

- (void)downloadFile:(NSString *)file
{
    NSLog(@"Download file : %@", file);

    fileName = file;
    NSString *url = [NSString stringWithFormat:@"http://temporaryServerUrl&fileName=%@", fileName];

    NSLog(@"URL : %@", url);

    NSMutableURLRequest *request=[NSMutableURLRequest requestWithURL:[NSURL URLWithString:url] cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:10.0];

 // create the connection with the request and start loading the data
    [request setHTTPMethod:@"GET"];
    [request setValue:[NSString stringWithFormat:@"text/plain,application/xml"] forHTTPHeaderField:@"Accept"];
    urlConnection =[[NSURLConnection alloc] initWithRequest:request delegate:self];

    if (urlConnection)
    {
        // Create the NSMutableData to hold the received data.
        receivedData = [[NSMutableData data] retain];
    }
    else
    {
        NSLog(@"HTTP connection failed to download file.");
    }

    NSLog(@"Run loop started");
    CFRunLoopRun();   // Avoid thread exiting
    NSLog(@"Run loop stoped");
}

- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace (NSURLProtectionSpace *)protectionSpace
{
    if ([NSURLAuthenticationMethodHTTPDigest compare:[protectionSpace authenticationMethod]] == NSOrderedSame)
    {
        return YES;
    }
    else
    {
        NSLog(@"Warning: Unsupported HTTP authentication method.");
    }

    return NO;
}

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge (NSURLAuthenticationChallenge *)challenge
{
    if ([challenge previousFailureCount] == 0)
    {
        NSURLCredential *newCredential;
        newCredential = [NSURLCredential credentialWithUser:@"admin" password:@"1234" persistence:NSURLCredentialPersistenceNone];
        [[challenge sender] useCredential:newCredential forAuthenticationChallenge:challenge];
    }
    else
    {
        NSLog(@"Going to cancel the authentication challenge.");
        [[challenge sender] cancelAuthenticationChallenge:challenge];
        // inform the user that the user name and password in the preferences are incorrect
    }
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    // This method is called when the server has determined that it
    // has enough information to create the NSURLResponse.  
    // It can be called multiple times, for example in the case of a
    // redirect, so each time we reset the data.

    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *) response;

    [receivedData setLength:0];
    receivedStatusCode = httpResponse.statusCode;

    if (httpResponse.statusCode == 200)
    {
            NSLog(@"200 ok received");
    }
    else
    {
        // We can also add condition that status code >= 400 for failure.
        NSLog(@"%d status code is received.", httpResponse.statusCode);
    }
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    // Append the new data to receivedData. receivedData is an instance variable declared elsewhere.
    if ([urlConnection isEqual:connection])
    {
        [receivedData appendData:data];
    }
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    // release the connection, and the data object
    [connection release];
    // receivedData is declared as a method instance elsewhere
    [receivedData release];

    // inform the user
    NSLog(@"Connection failed! Error domain - %@, error code %d, error discryption - %@", [error domain], [error code], [error localizedDescription]);

    // stop a CFRunLoop from running.
    CFRunLoopStop(CFRunLoopGetCurrent());
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    if ([urlConnection isEqual:connection] && (receivedStatusCode == 200))
    {
        NSString *filePath;
     NSString *rootPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    filePath = [rootPath stringByAppendingPathComponent:fileName];
    NSLog(@"File Path %@", filePath);

        NSString *data = [[[NSString alloc] initWithData:receivedData encoding:NSISOLatin1StringEncoding] autorelease];

        NSLog(@"Data : %@", data);
        [data writeToFile:filePath atomically:YES encoding:NSISOLatin1StringEncoding error:NULL];

    }
    else
    {
    }

    [urlConnection release];
    [receivedData release];

    // stop a CFRunLoop from running.
    CFRunLoopStop(CFRunLoopGetCurrent());
}

@end
4

1 回答 1

1

线程之间的通信是一个非常常见的问题，并且有很多可能的解决方案。

我看到的一种解决方案不是使用performSelectorInBackground:而是创建一个NSThread实例，保存线程引用并调用start. 然后您可以使用其中一种[NSObject performSelector:onThread:...]方法来调用停止方法（不要忘记在停止循环之前实际取消请求）。

另一种解决方案可能是在循环CFRunLoopRun内调用超时while，等待某些条件发生。查看 iPhone 中的答案：如何使用 performSelector:onThread:withObject:waitUntilDone: 方法？.

另一种解决方案是使用本地通知 ( NSNotificationCenter)。后台线程可以注册自己的通知，主线程可以在条件发生时发送它们。

于 2013-04-24T09:26:33.803 回答