After calling Reachability startNotifier, the Network status changes to 0 - ios

Question

in my iOS application, I need to use Reachability to complete the following tasks:
When a view controller is rendered, the application needs to check the connection status, and display the connection icon image accordingly (online or offline).
When the user stays on the view controller, and if the internet connection status changes, the application will be notified with the change, and then do some tasks accordingly.
I used the Reachability class which is produced by Tony Million in my application, but a strange thing happened:
After calling the startNotified method, the reachability status changes to 0(NotReachable).
The following is my code:
BTLandingViewController.h
#import <UIKit/UIKit.h>
#import "MBProgressHUD.h"
#import "Reachability.h"
#interface BTLandingViewController : UIViewController <UIAlertViewDelegate>
{
__weak IBOutlet UIImageView *internetIndicator;
MBProgressHUD *hud;
Reachability *reach;
UIAlertView *emptyRecordsAlert;
UIAlertView *syncReminderAlert;
}
#end
Part of the code in
BTLandingViewController.m
#import "BTLandingViewController.h"
#interface BTLandingViewController ()
#end
#implementation BTLandingViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Initialize reachability
reach = [Reachability reachabilityWithHostname:BTReachTestURL];
}
return self;
}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
// Register with reachability changed notification
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(reachabilityChanged:)
name:kReachabilityChangedNotification
object:nil];
NetworkStatus internetStatus = [reach currentReachabilityStatus]; // value = 1 or 2
***// PS: If there is connection, before [reach startNotifier], the internetStatus's value reflects the connection status (1 or 2)***
// Start notify reachability change
[reach startNotifier];
internetStatus = [reach currentReachabilityStatus]; // Value = 0;
***// PS: Even if there is connection, after [reach startNotifier], the internetStatus's value becomes 0***
}
Thank you for your help.

Answer 1

I have finally solved this problem by working around the startNotifier trap I mentioned above. Calling startNotifier does change the network status to 0, but I declare a variable to store the initial network status when the view controller is rendered. And then use the value of the variable in a if statement in the method which handles the action triggered by reachabilityChanged notification. The following is my code:
BTLandingViewController.h
#import <UIKit/UIKit.h>
#import "MBProgressHUD.h"
#import "Reachability.h"
#interface BTLandingViewController : UIViewController <UIAlertViewDelegate>
{
__weak IBOutlet UIImageView *internetIndicator;
MBProgressHUD *hud;
NSInteger initialNetworkStatus;
UIAlertView *emptyRecordsAlert;
UIAlertView *syncReminderAlert;
}
#end
BTLandingViewController.m
#import "BTLandingViewController.h"
#import "BTSyncEngine.h"
#import "BTInstructorLoginViewController.h"
#import "BTGlobalParams.h"
#interface BTLandingViewController ()
#end
#implementation BTLandingViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)viewDidUnload {
internetIndicator = nil;
[super viewDidUnload];
}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
// Register with sync complete notification
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(syncCompleted:) name:#"BTSyncEngineSyncCompleted" object:nil];
// Register with reachability changed notification
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(reachabilityChanged:)
name:kReachabilityChangedNotification
object:nil];
Reachability *reach = [Reachability reachabilityWithHostname:BTReachTestURL];
reach.reachableBlock = ^(Reachability * reachability){
dispatch_async(dispatch_get_main_queue(), ^{
initialNetworkStatus = 1;
[internetIndicator setImage:[UIImage imageNamed:#"online_indicator.png"]];
// Start syncing local records with the remote server
[[BTSyncEngine sharedEngine] startSync];
hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];
hud.labelText = #"Sync in progress";
});
};
reach.unreachableBlock = ^(Reachability * reachability)
{
dispatch_async(dispatch_get_main_queue(), ^{
initialNetworkStatus = 0;
[internetIndicator setImage:[UIImage imageNamed:#"offline_indicator.png"]];
// If the initial sync has been executed
// then use the cached records on the device
if ([[BTSyncEngine sharedEngine] initialSyncComplete]) {
// Go to instructor login screen
BTInstructorLoginViewController *instructorLoginViewController = [[BTInstructorLoginViewController alloc] init];
[instructorLoginViewController setModalTransitionStyle:UIModalTransitionStyleCrossDissolve];
[self presentViewController:instructorLoginViewController animated:YES completion:nil];
}
// If the initial sync has not been executed
// show an alert view
else {
emptyRecordsAlert = [[UIAlertView alloc] initWithTitle:#"Alert" message:#"Please connect to the internet to load data for the first time use." delegate:self cancelButtonTitle:nil otherButtonTitles:#"OK", nil];
[emptyRecordsAlert show];
}
});
};
[reach startNotifier];
}
- (void)viewDidDisappear:(BOOL)animated
{
[super viewDidDisappear:animated];
// Unregister with reachability changed notification
[[NSNotificationCenter defaultCenter] removeObserver:self name:kReachabilityChangedNotification object:nil];
// Unregister with sync complete notification
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"BTSyncEngineSyncCompleted" object:nil];
}
- (void)syncCompleted:(NSNotification *)note
{
// Update the global sync completed flag
[[BTGlobalParams sharedParams] setSyncCompleted:YES];
// Hide syncing indicator
[MBProgressHUD hideHUDForView:self.view animated:YES];
// Go to instructor login screen
BTInstructorLoginViewController *instructorLoginViewController = [[BTInstructorLoginViewController alloc] init];
[instructorLoginViewController setModalTransitionStyle:UIModalTransitionStyleCrossDissolve];
[self presentViewController:instructorLoginViewController animated:YES completion:nil];
}
- (void)reachabilityChanged:(NSNotification *)note
{
Reachability *reach = [note object];
if ([reach isReachable] && !initialNetworkStatus) {
[internetIndicator setImage:[UIImage imageNamed:#"online_indicator.png"]];
// Start syncing local records with the remote server
[[BTSyncEngine sharedEngine] startSync];
hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];
hud.labelText = #"Sync in progress";
}
}
#end