blocks|key|1942282|text|不幸的是，stringWithContentsOfURL是一个同步方法，这意味着它将阻塞您的线程，并且在它运行时您不会收到任何回调。这也不利于用户体验。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1942283|另一种方法是使用NSURLConnection手动设置您自己的请求，并点击连接的委托方法以显示某种进度条。具体地说，您需要使用connection:didReceiveData:和connectionDidFinishLoading:|1942284|收到所有数据后，使用以下命令获取字符串。|1942285|NSString+*theString+=+[[NSString+alloc]+initWithData:yourData+encoding:UTF8StringEncoding];|code-block|syntax|javascript|1942286|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.apple.com/library/ios/#documentation/Cocoa/Reference/Foundation/Classes/NSURLConnection_Class/Reference/Reference.html#//apple_ref/doc/uid/TP40003755^0|5|N|0|1R|Q|2I|R|8|F|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|C]]|D|@$9|14|A|15|1|16]]|E|$]]|$1|H|3|I|5|6|7|17|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|18|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|19|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

Unfortunately, <code>stringWithContentsOfURL</code> is a synchronous method, meaning it will block your thread and you will not receive any callbacks while it is running. This is also bad for user experience.

The alternative would be to use <a href="http://developer.apple.com/library/ios/#documentation/Cocoa/Reference/Foundation/Classes/NSURLConnection_Class/Reference/Reference.html#//apple_ref/doc/uid/TP40003755" rel="nofollow">NSURLConnection</a> to manually setup your own request, and tap into the delegate methods of your connection to display some sort of progress bar. Specifically, you'll want to use <code>connection:didReceiveData:</code> and <code>connectionDidFinishLoading:</code>

Once all the data has been received, use the following to get your string.

<pre><code>NSString *theString = [[NSString alloc] initWithData:yourData encoding:UTF8StringEncoding];
</code></pre>

blocks|key|203361|text|这是“延迟加载”的典型案例。请参阅Apple的示例代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|203362|http://developer.apple.com/library/ios/#samplecode/LazyTableImages/Introduction/Intro.html|offset|length|203363|在阅读代码时，用“string”替换"images“应该很容易。|203364|您希望在标签中显示一个占位符，如"(fetching+information)“或类似的，然后在后台加载信息，要么自己线程化fetch+(异步fetching)，要么使用像ASIHTTPRequest这样的库为您处理所有异步螺母和螺栓，并在fetch完成后调用委托方法。|203365|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|2I|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@$D|S|E|T|1|U]]|A|$]]|$1|F|3|G|5|6|7|V|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|W|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|K|$L|$5|M|N|O|A|$P|C]]]]

This is a classic case for "Lazy Loading". See Apple's example code:

<a href="http://developer.apple.com/library/ios/#samplecode/LazyTableImages/Introduction/Intro.html" rel="nofollow">http://developer.apple.com/library/ios/#samplecode/LazyTableImages/Introduction/Intro.html</a>

It should be easy to substitute "strings" for "images" as you read that code.

You want to display a placeholder in the label like "(fetching information)" or similar and then load the information in the background, either threading the fetches yourself (asynchronous fetching) or using a library like ASIHTTPRequest that handles all the asynchronous nuts and bolts for you, calling a delegate method once the fetch has completed.

blocks|key|3842073|text|要使此方法异步，可以并推荐使用中央调度中心。如果任何人感兴趣，我将展示几行代码来做到这一点。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3842074|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

To make this method asynch it is possible and recommendable to use Grand Central Dispatch. If anyone is interested I will show the few lines of code to do that.

blocks|key|203381|text|尝尝这个。它在后台加载数据。如果稍后更新UI+(在异步加载中)，请确保在主线程上执行此操作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|203382|-(void)loadappdetails:(NSString*)appid+{
++++NSString*+searchurl+=+[@"https://itunes.apple.com/lookup?id="+stringByAppendingString:appid];

++++[self+performSelectorInBackground:@selector(asyncload:)+withObject:searchurl];

}
-(void)asyncload:(NSString*)searchurl+{
++++NSURL*+url+=+[NSURL+URLWithString:searchurl];
++++NSError*+error+=+nil;
++++NSString*+str+=+[NSString+stringWithContentsOfURL:url+encoding:NSUTF8StringEncoding+error:&error];
++++if+(error+!=+nil)+{
++++++++NSLog(@"Error:+%25@",+error);
++++}
++++NSLog(@"str:+%25@",+str);
}|code-block|syntax|javascript|203383|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try this. It loads stuff in background. If updating the UI later (in asyncload), be sure to do that on main thread.

<pre><code>-(void)loadappdetails:(NSString*)appid {
 NSString* searchurl = [@"https://itunes.apple.com/lookup?id=" stringByAppendingString:appid];

 [self performSelectorInBackground:@selector(asyncload:) withObject:searchurl];

}
-(void)asyncload:(NSString*)searchurl {
 NSURL* url = [NSURL URLWithString:searchurl];
 NSError* error = nil;
 NSString* str = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&amp;error];
 if (error != nil) {
 NSLog(@"Error: %@", error);
 }
 NSLog(@"str: %@", str);
}
</code></pre>

I am using stringWithcontentsofurl to download some strings from my web server to the App, but i would like to update the UI to show A loader of some kind. I am downloading a number of strings (it can be sometimes as much as 100) so it would be neat for the user to show something so they know the App isn't crashing, because now the UI is stuck, i can't show A UILoader or something like that. Is there an option to do so? Or maybe A alternative to stringWithcontentsofurl where this is possible?

greets,
Erik

Update UI when using stringWithContentsofurl

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在使用stringWithcontentsofurl从我的web服务器下载一些字符串到应用程序，但我想更新UI以显示某种类型的加载器。我正在下载一些字符串(有时可能多达100个)，所以用户可以显示一些东西，这样他们就知道应用程序不会崩溃，因为现在UI卡住了，我不能显示UILoader或类似的东西。有这样做的选择吗？...

问使用stringWithContentsofurl时更新UI
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