performSelectorOnMainThread 和detachNewThreadSelector区别.

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{

[NSThread detachNewThreadSelector:@selector(threadFunc:) toTarget:self withObject:(id)userInfor];

}

- (void)threadFunc:(id)userInfor{

NSAutoreleasePool*pool = [[NSAutoreleasePool alloc] 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 = [NSThread currentThread];

self.uploadPool = [[NSAutoreleasePool alloc] init];
self.characterBuffer = [NSMutableData data];
done = NO;
[[NSURLCache sharedURLCache] removeAllCachedResponses];

NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:[NSURLURLWithString:url]];

self.connection = [[NSURLConnection alloc] 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;
}