iphone开发第五课：performSelectorOnMainThread 和detachNewThreadSelector区别-优快云博客

本文介绍如何使用Objective-C中的NSThread类创建子线程，并演示了一个具体的例子：在一个子线程中下载图片。文章详细展示了创建线程、处理下载任务及通知主线程更新界面的过程。

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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;
}