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copied!<p>I give an answer to my own question. Finding out the solution took me a while and was quite frustrating. If you do an internet search you find some partial answers, but it still took me a while to work out the following solution and I do hope it adds some clarity.</p> <p>So first, the recommended behavior of your app appears to be the following (see <a href="http://developer.apple.com/iphone/library/documentation/iphone/conceptual/iphoneosprogrammingguide/StandardBehaviors/StandardBehaviors.html#//apple_ref/doc/uid/TP40007072-CH4-SW20" rel="noreferrer">Opening Supported File Types</a> in iOS Ref Lib):</p> <ul> <li>Do not implement <code>applicationDidFinishLaunching:</code> (see the note at <a href="http://developer.apple.com/iphone/library/documentation/UIKit/Reference/UIApplicationDelegate_Protocol/Reference/Reference.html#//apple_ref/occ/intfm/UIApplicationDelegate/application:didFinishLaunchingWithOptions:" rel="noreferrer">UIApplicationDelegate</a>).</li> <li>Implement <code>application:didFinishLaunchingWithOptions:</code> and check the URL, return YES if you can open it, otherwise NO, but do not open it.</li> <li>Implement <code>application:handleOpenURL:</code> and open the URL, return YES if successful, otherwise NO.</li> </ul> <p>In iOS 4, passing an URL to an app results in one of the following two behaviors:</p> <ul> <li>If the app is launched then <code>application:didFinishLaunchingWithOptions:</code> is called and <code>application:handleOpenURL:</code> is called if and <code>application:didFinishLaunchingWithOptions:</code> returned YES.</li> <li>If the app is becoming active from suspended state then <code>application:didFinishLaunchingWithOptions:</code> is not called but <code>application:handleOpenURL:</code> is called.</li> </ul> <p>However, in iOS 3.2 it appears as if <code>application:handleOpenURL:</code> is never called! A hint that the behavior is different under iOS 3.2 can be found in <a href="http://developer.apple.com/iphone/library/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/StandardBehaviors/StandardBehaviors.html#//apple_ref/doc/uid/TP40007072-CH4-SW14" rel="noreferrer">Handling URL Requests</a>. There you find that <code>application:handleOpenURL:</code> is called if <code>application:didFinishLaunchingWithOptions:</code> is not implemented, but <code>applicationDidFinishLaunching:</code> is implemented. But <code>application:handleOpenURL:</code> is not called if <code>application:didFinishLaunchingWithOptions:</code> is implemented.</p> <p>Hence, one solution to make the code work under 3.2 and 4.0 is:</p> <ul> <li>Open the URL in <code>application:didFinishLaunchingWithOptions:</code>, but then return NO to prevent that <code>application:handleOpenURL:</code> is called.</li> <li>Open the URL in <code>application:handleOpenURL:</code>, in case you are under 4.0 and the app was in suspended state.</li> </ul> <p>I found this solution in another post, but I was confused, because it contradicted the recommendation in iOS Ref Lib documentation (namely that we should return YES in <code>application:didFinishLaunchingWithOptions:</code>). (At that point I did not realize that the documentation contradicts it self).</p> <p>I believe that the current iOS 4.0 behavior will be the future behavior I prefer the following solution:</p> <ul> <li>Do not implement <code>applicationDidFinishLaunching:</code>.</li> <li>Implement <code>application:didFinishLaunchingWithOptions:</code> and check the URL, return YES if you can open it, otherwise NO, but do not open it. If we are on 3.2, open the URL.</li> <li>Implement <code>application:handleOpenURL:</code> and open the URL, return YES if successful, otherwise NO.</li> </ul> <p>So in summary, I implement the iOS 4 behavior and added the following line to <code>application:didFinishLaunchingWithOptions:</code></p> <p><code> <PRE> if([[[UIDevice currentDevice] systemVersion] hasPrefix:@"3.2"]) { [self application:application handleOpenURL:url]; } </PRE> </code></p> <p>which make the code work under 3.2.</p>

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