I downloaded the latest AdMob SDK for iOS, but I have a problem with the banner offset, as shown in the following figure

Here is the code that I use to show its positioning
bannerView = [[GADBannerView alloc] initWithAdSize:kGADAdSizeBanner];
CGRect bannerFrame = bannerView.frame;
bannerFrame.origin.y = [[UIScreen mainScreen] bounds].size.height - bannerFrame.size.height;
[bannerView setFrame:bannerFrame];
bannerView.adUnitID = AD_NOB_BANNER_UNIT_ID;
bannerView.rootViewController = self;
[self.view addSubview:bannerView];
[bannerView loadRequest:[GADRequest request]];
I set the background color to green and the background color of the banner to gray to check if it is positioned correctly or not. The correct cell position is {{0, 430}, {320, 50}}, but the banner has an incorrect offset.
If I go to him with my finger, I can scroll it up and it will fit the screen ... but its bias is wrong, if I scroll down, I see the same bias problem. Apparently, I did not find any way to set this offset.
Has someone encountered and solved the same problem?