iOS多线程

转自：http://www.189works.com/article-16880-1.html

举例说明怎么简单的创建一个子线程。
用到的类是NSThread类，这里使用detachNewTheadSelector:toTagaet:withObject创建一个线程。
函数setupThread:(NSArray*)userInfor。通过userInfor将需要的数据传到线程中。
函数定义：
-(void)setupThread:(NSArray*)userInfor{
   [NSThreaddetachNewThreadSelector:@selector(threadFunc:)
toTarget:self withObject:(id)userInfor];
}
- (void)threadFunc:(id)userInfor{
  NSAutoreleasePool*pool = [[NSAutoreleasePoolalloc] init];
  //。。。。需要做的处理。
   //这里线程结束后立即返回
[self performSelectorOnMainThread:@selector(endThread) withObject:nil
waitUntilDone:NO];
[pool release];
}
performSelectorOnMainThread通知主线程执行函数endThread。也可以使用performSelector:onThread:withObject:waitUntil
通知某线程执行线程结束后的处理。
线程内不要刷新界面。如果需要刷新界面，通过performSelectorOnMainThread，调出主线程中的方法去刷新。
例如，启动一个线程下载图片：
//启动线程
[NSThread
detachNewThreadSelector:@selector(downloadImage:) toTarget:self
withObject:url];
//线程函数
- (void)
downloadImage:(NSString*)url{
_subThreed = [NSThreadcurrentThread];
self.uploadPool = [[NSAutoreleasePoolalloc] init];
    self.characterBuffer = [NSMutableDatadata];
    done
= NO;
    [[NSURLCache sharedURLCache]
removeAllCachedResponses];
NSMutableURLRequest *theRequest = [NSMutableURLRequestrequestWithURL:[NSURLURLWithString:url]];
self.connection = [[NSURLConnectionalloc] initWithRequest:theRequest
delegate:self];
    [self
performSelectorOnMainThread:@selector(httpConnectStart) withObject:nil
waitUntilDone:NO];
    if (connection !=
nil) {
        do {
            [[NSRunLoop currentRunLoop]
runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
        } while (!done);
    }
self.photo = [UIImage imageWithData:characterBuffer];
   //下载结束，刷新
    [self
performSelectorOnMainThread:@selector(fillPhoto) withObject:nil
waitUntilDone:NO];
    // Release resources used only
in this thread.
    self.connection =
nil;
    [uploadPool
release];
    self.uploadPool =
nil;
    _subThreed = nil;
}
#pragma mark NSURLConnection
Delegate methods
/*
Disable caching so that each time
we run this app we are starting with a clean slate. You may not want to do this
in your application.
*/
- (NSCachedURLResponse *)connection:(NSURLConnection
*)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse
{
    return nil;
}
// Forward errors to the
delegate.
-
(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    done = YES;
    [self
performSelectorOnMainThread:@selector(httpConnectEnd) withObject:nil
waitUntilDone:NO];
    [characterBuffer
setLength:0];
}
// Called when a chunk of data has
been downloaded.
-
(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    // Process
the downloaded chunk of data.
[characterBuffer appendData:data];
}
-
(void)connectionDidFinishLoading:(NSURLConnection *)connection {
    [self
performSelectorOnMainThread:@selector(httpConnectEnd) withObject:nil
waitUntilDone:NO];
    // Set the condition which
ends the run loop.
    done =
YES;
}