+ detachNewThreadSelector:toTarget:withObject: 和 - performSelectorInBackground:withObject: 的效果基本一致,如果不打算支持iOS3的話，用GCD要方便很多很多
performSelectorOnMainThread是指在主線程上執行某個方法，比如數據下載后，更新UI界面等操作
舉例說明怎么簡單的創建一個子線程。
用到的類是NSThread類，這里使用detachNewTheadSelector:toTagaet:withObject創建一個線程。
函數setupThread:(NSArray*)userInfor。通過userInfor將需要的數據傳到線程中。
函數定義：
-(void)setupThread:(NSArray*)userInfor{
[NSThread detachNewThreadSelector:@selector(threadFunc:) toTarget:self withObject:(id)userInfor];
}
- (void)threadFunc:(id)userInfor{
NSAutoreleasePool*pool = [[NSAutoreleasePool alloc] init];
//。。。。需要做的處理。
//這里線程結束后立即返回
[self performSelectorOnMainThread:@selector(endThread) withObject:nil waitUntilDone:NO];
[pool release];
}
performSelectorOnMainThread通知主線程執行函數endThread。也可以使用performSelector:onThread:withObject:waitUntil 通知某線程執行線程結束后的處理。
線程內不要刷新界面。如果需要刷新界面，通過performSelectorOnMainThread，調出主線程中的方法去刷新。
例如，啟動一個線程下載圖片：
//啟動線程
[NSThread detachNewThreadSelector:@selector(downloadImage:) toTarget:self withObject:url];
//線程函數
- (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];
//下載結束，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;
}