viewDidUnload帮助 - iPhone应用程序

Question

I'm having trouble with the new iOS 6. Previously I understood "viewDidUnload". It's my understanding that this is now depreciated and I'm having some issues with ending the networks activity indicator. Below is my code. Thanks in advance for your help!

#import "MapViewController.h"

@implementation MapViewController

@synthesize webview, url, activityindicator, searchbar;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) 
    {
        // Custom initialization.
    }
    return self;
}

- (void)viewDidLoad 
{
    NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];
    webview.delegate = self;
    activityindicator.hidden = TRUE;
    [webview performSelectorOnMainThread:@selector(loadRequest:) withObject:requestObj waitUntilDone:NO];
    [super viewDidLoad];
}

- (void)webViewDidFinishLoad:(UIWebView *)webView 
{
    activityindicator.hidden = TRUE;  
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    [activityindicator stopAnimating];  
    NSLog(@"Web View started loading...");
}

- (void)webViewDidStartLoad:(UIWebView *)webView {     
    activityindicator.hidden = FALSE;
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
    [activityindicator startAnimating];     
    NSLog(@"Web View Did finish loading");
}

- (void)didReceiveMemoryWarning {
        // Releases the view if it doesn't have a superview.
        [super didReceiveMemoryWarning];

        // Release any cached data, images, etc. that aren't in use.
}

- (void)viewDidUnload {
    webview = nil;
    activityindicator = nil;
    searchbar = nil;
    [super viewDidUnload];
}

- (void)dealloc {
    [url release];
    [super dealloc];
}

@end

Answer 1

I think you misunderstand what viewDidUnload is for. Your code shows nothing to do with hiding the activity spinner in viewDidUnload .

- (void)viewDidUnload
{
  webview = nil;
  activityindicator = nil;
  searchbar = nil;
  [super viewDidUnload];
}

viewDidUnload was only ever meant for cleaning up retained, replaceable objects when the system had purged your UIViewController's inactive view during a case of low memory.

In iOS 6 viewDidUnload is never called, because the system will no longer purge a UIViewController's view in low memory situations, it's up to you to do that if you need too in the didReceiveMemoryWarning callback.

- (void)didReceiveMemoryWarning
{
  [super didReceiveMemoryWarning];
  if ([self isViewLoaded] && self.view.window == nil)
  {
    self.view = nil;
    [self viewDidUnload];
   }
}