Iphone 用iAds解除ModalViewController。横幅视图有广告，但可能会被遮挡

这是我的问题。我有一个使用PresentModalViewAnimated显示的登录屏幕。一旦用户登录，它将被解除

在登录屏幕上，我有一个iAd，但当它被解除时，我得到这个错误

ADBannerView：警告横幅视图0x5a37df0有广告，但可能是 模糊的。此消息仅在每个条幅视图中打印一次

另外，当我登录然后注销时，iAd不会再次显示

我的代码片段

    @synthesize bannerIsVisible;

- (void)bannerViewDidLoadAd:(ADBannerView *)banner
{
    if (!self.bannerIsVisible)
    {
        [UIView beginAnimations:@"animateAdBannerOn" context:NULL];
        // banner is invisible now and moved out of the screen on 50 px
        banner.frame = CGRectOffset(banner.frame, 0, 50);
        [UIView commitAnimations];
        self.bannerIsVisible = YES;
    }
}

- (void)bannerView:(ADBannerView *)banner didFailToReceiveAdWithError:(NSError *)error
{
    if (self.bannerIsVisible)
    {
        [UIView beginAnimations:@"animateAdBannerOff" context:NULL];
        // banner is visible and we move it out of the screen, due to connection issue
        banner.frame = CGRectOffset(banner.frame, 0, -50);
        [UIView commitAnimations];
        self.bannerIsVisible = NO;
    }
}

- (BOOL)bannerViewActionShouldBegin:(ADBannerView *)banner willLeaveApplication:(BOOL)willLeave
{
    NSLog(@"Banner view is beginning an ad action");
    BOOL shouldExecuteAction = YES;
    if (!willLeave && shouldExecuteAction)
    {
        // stop all interactive processes in the app
        // [video pause];
        // [audio pause];
    }
    return shouldExecuteAction;
}

- (void)bannerViewActionDidFinish:(ADBannerView *)banner
{
    // resume everything you've stopped
    // [video resume];
    // [audio resume];
}


    - (void)viewDidLoad
{
    interestingTags = [[NSSet alloc] initWithObjects: INTERESTING_TAG_NAMES2]; //set interestingTag var to define
    self.userArray = [[NSMutableArray alloc] init]; //init the userArray

    adView = [[ADBannerView alloc] initWithFrame:CGRectZero];
    adView.frame = CGRectOffset(adView.frame, 0, -50);
    adView.requiredContentSizeIdentifiers = [NSSet setWithObject:ADBannerContentSizeIdentifierPortrait];
    adView.currentContentSizeIdentifier = ADBannerContentSizeIdentifierPortrait;
    [self.view addSubview:adView];

    adView.delegate=self;
    self.bannerIsVisible=NO;

    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
}

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我认为这样可以消除错误。只需删除视图中的横幅视图就会消失：

-(void)viewWillDisappear:(BOOL)animated
{
    [bannerView removeFromSuperview];
}

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许多关于这方面的好信息已经在