Edit: As noted in the comments, this technique no longer works in iPhone OS 3.1.
If you are writing an iPhone GameKit app without using GKPeerPickerController (as I did in PhotoBeamer), you need to detect when Bluetooth is disabled and ask the user to turn it on in the settings app. Apple doesn’t provide a way for a developer to enable Bluetooth other than through GKPeerPickerController.
This is pretty easy to do. First, create your GKSession and set it to be available:
session = [[GKSession alloc] initWithSessionID:kMyAppSessionID displayName:nil sessionMode:GKSessionModeClient]; session.delegate = self; [session setDataReceiveHandler:self withContext:nil]; session.available = YES;
Next, set up your - (void)session:(GKSession *)session didFailWithError:(NSError *)error delegate method to detect when Bluetooth is not available and alert the user:
// GKSessionErrorDomain causes link error (rdar://problem/7014349) #if 0 #define kGKSessionErrorDomain GKSessionErrorDomain #else #define kGKSessionErrorDomain @"com.apple.gamekit.GKSessionErrorDomain" #endif - (void)session:(GKSession *)session didFailWithError:(NSError *)error { if ([[error domain] isEqual:kGKSessionErrorDomain] && ([error code] == GKSessionCannotEnableError)) { // Bluetooth disabled, prompt the user to turn it on } else { // Some other error, get the description from the NSError object } // destroy the GKSession and clean up }
The GKSessionErrorDomain symbol causes a link error for me, so I’m temporarily using the constant string instead. When Apple fixes the SDK, I’ll change that #if 0 to use the official symbolic name.
Note that this error will sometimes occur on a reconnection attempt even when Bluetooth is enabled, presumably because the old session is still partially active.
It would be nice to have a more user-friendly way to turn on Bluetooth without leaving the app and without using the full GKPeerPickerController UI. I’ve filed a bug report (rdar://problem/7061502) asking for this functionality. You should file one too.
