iphone开发-多线程

+ detachNewThreadSelector:toTarget:withObject: 和 - performSelectorInBackground:withObject: 的效果基本一致,如果不打算支持iOS3的话，用GCD要方便很多很多

performSelectorOnMainThread是指在主线程上执行某个方法，比如数据下载后，更新UI界面等操作

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; 
}