无法删除观察者

Question

- (void)viewWillAppear:(BOOL)animated
{
MKUserTrackingBarButtonItem *trackingBarButtonItem = [[MKUserTrackingBarButtonItem alloc]initWithMapView:_mapView];

NSArray *barButtonItems = [NSArray arrayWithObjects:trackingBarButtonItem, nil];
mapToolbar.items = barButtonItems;
...
}

代码在iPhone上运行正常，但在iPad上卸载视图时出现错误：

Cannot remove an observer <MKUserTrackingBarButtonItem 0x9cc0930> for the key path  
"controlSize" from <UIButton 0x991b420> because it is not registered as an observer.'

Answer 1

我联系了Apple DTS，答案是：

“据我所知，目前的发货SDK没有解决方法。我会查看最新的iOS SDK测试版，看看这是否还是个问题。”