iPhone App in suspended state, launched by URL, showing Default.png

The app responds to a custom URL, and correctly launches when in a suspended state. The question is, can I disable showing the Default.png when launched this way?

A use case for clarity:

1. app is started normally
2. a home button press puts app in standby
3. a url of the scheme the app recognizes is tapped in mobile safari
4. users sees Default.png before launch is complete.

As you probably know, when fast app switching activates usually the app is redisplayed with a screenshot of the last state rather than the Default.png. This is what I'd prefer happens when the URL launch takes plac开发者_Python百科e also.

It sounds like what is going on is that Fast App Switching is not actually working. So:

1. Make sure you are building the application for SDK for OS 4.0. If you don't, you app will not have fast app switching support.

2. See if fast app switching normally (otherwise) works with your application. I.E. when you just switch to safari, then re-launch your application, do you get the "default.png"?

3. Run the app under the debugger, but on your actual device. Make the problem happen, go into the Organizer, and look under device logs. This will show you if there was a low-memory issue which caused your application to be terminated, when Safari was launched, thus requiring it to be re-launched when the URL was selected.

4. I believe there were two mechanisms in place. In my app, I do not support "Launch with URL" - but what I do do is support the Application Delegate's call:

-(BOOL) application:(UIApplication *) application handleOpenURL:(NSURL *) url {

This may be the difference - this is the call which can be made to an application that is running to hand it a URL to process. If you are using the other technique, use this one instead. I use this, and do not see the "default.png" - i.e. do not evoke a "clean relaunch" when I get called.

Here's a possible workaround. This was causing me a headache with trying to seamlessly return from Facebook's single sign on process. I wanted the appearance of going back to my app's login area, instead of the appearance of restarting the app, even though I verified in every way possible that the app was indeed returning from fast app switching and not actually restarting.

While I couldn't find any way to force the app to display the previous state's screenshot, I did discover that the app will display Default-scheme.png (for example, Default-fb12345.png or Default-appname.png) when invoked with a url. So if your post-app switching screenshot is fairly predictable, grab a screenshot from iOS Simulator and copy it into your app. I would consider this an iOS bug. The app should always display the last screenshot when app switching, rather than Default-scheme.png simply because a url is involved.

Another possibility, which I didn't test, would be to symlink the bundle's Default-scheme.png (and Default-scheme@2x.png) to the snapshot file in the app home directory. This would be Library/Caches/Snapshots/[Bundle identifier]/UIApplicationAutomaticSnapshotDefault-Portrait@2x.jpg for most situations (unless it's landscape, or an iPad). If your app's state is unpredictable but the orientation is fixed, this could be a good option to try.

Make sure you've got the "Required Background Modes" key set in the Info.plist to the function that the app needs. If it's not listed, I just use "App Plays Audio" to keep it open.