爲什麼KVO不能在UIView子類上工作？

Question

我有一個UIView子類，又具有內容查看，在公共頭宣佈爲：

@property (nonatomic,retain)UIVivew* contentView; 

我試圖讓國際志願者組織的通知，只要內容查看的框架發生改變，但observeValueForKeyPath方法不被永遠叫在我的UIView子類：

@implementation MyView 


@synthesize contentView = _contentView; 


- (id)initWithFrame:(CGRect)frame 
{ 
    self = [super initWithFrame:frame]; 
    if (self) { 
     // Initialization code 

     [self.contentView addObserver:self 
          forKeyPath:@"frame" 
           options:(NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld) 
           context:nil]; 
    } 
    return self; 
} 

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { 
    if ([keyPath isEqualToString:@"frame"]) { 
     CGRect newContentFrame = [[change objectForKey:NSKeyValueChangeNewKey] CGRectValue]; 
     CGRect selfNewFrame = self.frame; 
     selfNewFrame.size = CGSizeMake(newContentFrame.size.width + 10, newContentFrame.size.height + 10); 
     self.frame = selfNewFrame; 
    } 

    [super observeValueForKeyPath:keyPath ofObject:object change:change context:context]; 
} 

任何想法爲什麼KVO不開火？

Answer 1

對不起......睡眠剝奪我猜...

忘了分配/初始化的內容查看。