@interface ViewController () <UIWebViewDelegate>
@property (weak, nonatomic) IBOutlet UIWebView *webView;
@property (weak, nonatomic) UIBarButtonItem *backBarButtonItem;
@end

#pragma mark - Initialization

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self.webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"https://mobile.twitter.com/appstore"]]];
}

#pragma mark - Target Actions

- (void)goBackClicked:(UIBarButtonItem *)sender {
    [self.webView goBack];
}

#pragma mark - UIWebViewDelegate

- (void)webViewDidStartLoad:(UIWebView *)webView {
    NSLog(@"webViewDidStartLoad.");
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
    [self updateNavigationBar];
}

- (void)webViewDidFinishLoad:(UIWebView *)webView {
    NSLog(@"webViewDidFinishLoad  - %@", webView.request.URL.absoluteString);
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
    [self updateNavigationBar];
}

- (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error {
    NSLog(@"didFailLoadWithError.");
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
    [self updateNavigationBar];
}

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
    NSLog(@"shouldStartLoadWithRequest.");
    return true;
}