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在日常应用中,我们往往使用AFNetworking等第三方库来实现网络请求部分。这篇文章会简要地介绍一下如何使用NSURLConnection来进行异步的网络请求。
我们先看一个小demo
- (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. NSString *urlStr = @"http://www.baidu.com"; NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:urlStr]]; //从这个试验可以看出,connection的函数在 mainrunloop运行for循环时根本无法被调用,由此可见,这里的connection是在mainThread中运行的。 NSURLConnection *con = [[NSURLConnection alloc] initWithRequest:request delegate:self]; for(int i = 0 ;i<10000;i++) { NSLog(@"%d",i); } NSLog(@"for end=========="); } - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { NSLog(@"good!!!!!!!!"); }
看下输入
2014-05-05 10:34:18.861 UrlConnectionASyncTest[9988:60b] 9997 2014-05-05 10:34:18.862 UrlConnectionASyncTest[9988:60b] 9998 2014-05-05 10:34:18.862 UrlConnectionASyncTest[9988:60b] 9999 2014-05-05 10:34:18.862 UrlConnectionASyncTest[9988:60b] for end========== 2014-05-05 10:34:18.865 UrlConnectionASyncTest[9988:60b] good!!!!!!!!
查看苹果的文档会发现如下的解释
By default, a connection is scheduled on the current thread in the default mode when it is created. If you create a connection with the initWithRequest:delegate:startImmediately: method and provide NO for the startImmediately parameter, you can instead schedule the connection on an operation queue before starting it with the start method. You cannot reschedule a connection after it has started.
这就是说,如果你仅仅通过在主线程中使用initWithRequest:delegate:方法创建一个connection对象,它会默认地加入到mainThread中,这样当数据返回时,会在main thread中执行,这就会影响UI的刷新。这种connnection不是同步的connection,因为它在没有得到数据时就可以继续执行其他代码,但也不是那种真正的异步connection,因为它的回调函数会在main thread中执行,会影响main thread中的其他函数执行。
那么如何创建一个在其他thread中执行回调函数的connection呢?系统提供了2套方法,
第一套是使用类方法,sendAsynchronousRequest:queue:completionHandler:
第二套是使用几个对象方法,顺序如下
1.使用initWithRequest:delegate:startImmediately:生成一个不立即开始的connnection 2.通过scheduleInRunLoop:forMode: 或者 setDelegateQueue: 设置回调方法运行的thread,推荐使用第二个。 3.调用start开始connection请求。
下面给出一个demo
- (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. NSString *urlStr = @"http://www.baidu.com"; NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:urlStr]]; //从这个试验可以看出,connection的函数在 mainrunloop运行for循环时根本无法被调用,由此可见,这里的connection是在mainThread中运行的。 // NSURLConnection *con = [[NSURLConnection alloc] initWithRequest:request delegate:self]; NSURLConnection *con = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO]; [con setDelegateQueue:[[NSOperationQueue alloc] init]]; [con start]; for(int i = 0 ;i<10000;i++) { NSLog(@"%d",i); } NSLog(@"for end=========="); } - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { // NSLog(@"data is %@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]); NSLog(@"good!!!!!!!!"); }
结果如下
2014-05-05 11:23:15.129 UrlConnectionASyncTest[10147:60b] 344 2014-05-05 11:23:15.129 UrlConnectionASyncTest[10147:60b] 345 2014-05-05 11:23:15.129 UrlConnectionASyncTest[10147:60b] 346 2014-05-05 11:23:15.129 UrlConnectionASyncTest[10147:60b] 347 2014-05-05 11:23:15.129 UrlConnectionASyncTest[10147:60b] 348 2014-05-05 11:23:15.129 UrlConnectionASyncTest[10147:60b] 349 2014-05-05 11:23:15.130 UrlConnectionASyncTest[10147:60b] 350 2014-05-05 11:23:15.134 UrlConnectionASyncTest[10147:4207] good!!!!!!!! 2014-05-05 11:23:15.143 UrlConnectionASyncTest[10147:60b] 351 2014-05-05 11:23:15.144 UrlConnectionASyncTest[10147:60b] 352 2014-05-05 11:23:15.144 UrlConnectionASyncTest[10147:4207] good!!!!!!!! 2014-05-05 11:23:15.144 UrlConnectionASyncTest[10147:60b] 353 2014-05-05 11:23:15.144 UrlConnectionASyncTest[10147:60b] 354 2014-05-05 11:23:15.144 UrlConnectionASyncTest[10147:60b] 355 2014-05-05 11:23:15.145 UrlConnectionASyncTest[10147:60b] 356
可以看出connection的回调函数已经不再main thread中执行了!
iOS NSURLConnection和异步网络请求,布布扣,bubuko.com
标签:style blog class code java tar
原文地址:http://www.cnblogs.com/breezemist/p/3708808.html