Wednesday, May 13, 2009
iPhone: Detect online network status
Wednesday, May 13, 2009 
For my previous post I showed you how you can cache in memory images from URLs... however, what if the device is not able to connect to a network? The previous example will hang and eventually bomb back to the springboard because it's not coded to handle that condition.
For me this network detection thing was a bit of a Holy Grail item. I'd seen a few examples around from Apple that seemed like they used tons of code to get the job done (or maybe I just didn't understand their code well enough yet). Then I read online about a seismic XML tutorial from Apple that did network detection.
I popped open the project in the Xcode Documentation window and started checking out the .h and .m files. I saw the implementation they used, and it didn't involve tons of code. And after testing it, it works just fine for the moment.
I've since been told that I could use a separate thread and populate the initial UIImageViews with a stock image, and the threaded process would fetch and place the artwork as needed (to allow for initial smooth scrolling). I don't know enough about that yet though, so this will have to do.
Make sure you Add the SystemConfiguration.framework to your project, and include it in your .m (#import).
In your .h file, define a BOOL, I called mine "availableNetwork" - you don't need to assign it as a property, just up in the interface block. Make sure you also define the method in the .h... -(BOOL)isDataSourceAvailable;
Here are the two methods I'm using to report back network status (in my .m):
For me this network detection thing was a bit of a Holy Grail item. I'd seen a few examples around from Apple that seemed like they used tons of code to get the job done (or maybe I just didn't understand their code well enough yet). Then I read online about a seismic XML tutorial from Apple that did network detection.
I popped open the project in the Xcode Documentation window and started checking out the .h and .m files. I saw the implementation they used, and it didn't involve tons of code. And after testing it, it works just fine for the moment.
I've since been told that I could use a separate thread and populate the initial UIImageViews with a stock image, and the threaded process would fetch and place the artwork as needed (to allow for initial smooth scrolling). I don't know enough about that yet though, so this will have to do.
Make sure you Add the SystemConfiguration.framework to your project, and include it in your .m (#import
In your .h file, define a BOOL, I called mine "availableNetwork" - you don't need to assign it as a property, just up in the interface block. Make sure you also define the method in the .h... -(BOOL)isDataSourceAvailable;
Here are the two methods I'm using to report back network status (in my .m):
- (BOOL)isDataSourceAvailable {
static BOOL checkNetwork = YES;
static BOOL _isDataSourceAvailable = NO;
if (checkNetwork) { // Since checking the reachability of a host can be expensive, cache the result and perform the reachability check once.
checkNetwork = NO;
Boolean success;
const char *host_name = "google.com"; //pretty reliable :)
SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithName(NULL, host_name);
SCNetworkReachabilityFlags flags;
success = SCNetworkReachabilityGetFlags(reachability, &flags);
_isDataSourceAvailable = success && (flags & kSCNetworkFlagsReachable) && !(flags & kSCNetworkFlagsConnectionRequired);
CFRelease(reachability);
}
return _isDataSourceAvailable;
}That's the method we'll call when we load our view, and set our "availableNetwork" value to. loadView is triggered before viewDidLoad.- (void)loadView {
availableNetwork = NO;
BOOL returnVal = [self isDataSourceAvailable];
availableNetwork = returnVal;
...And there you have it. It's a one shot deal here, if connectivity returns, the flag won't be reset. You could always run a NSTimer that checks every now and then, or I am sure there is some kind of notification of that kind of change one could listen for... I'm not far enough along with all of this to know yet.Labels: iPhone, Network Status, Objective-C
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