Question

我有一个包含一些视图和自定义uiview的视图控制器。当我用手指触摸屏幕时，由于自定义uiview，我画了一条线。

为此，我将location.x和location.y通过通知中心发送到我的自定义uiview

CGPoint location = [touch locationInView:self.view];
userInfo = [NSMutableDictionary dictionary];
[userInfo setObject:[NSNumber numberWithFloat:location.x] forKey:@"x"];
[userInfo setObject:[NSNumber numberWithFloat:location.y] forKey:@"y"];
[[NSNotificationCenter defaultCenter] postNotificationName:@"addLine" object:self userInfo:userInfo];

在我的自定义uiview中，我以这种方式收到所有内容：

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(addLine:) name:@"addLine" object:nil];
NSDictionary* userInfo = notification.userInfo;
float x = [[userInfo objectForKey:@"x"] floatValue];
float y = [[userInfo objectForKey:@"y"] floatValue];
p = CGPointMake(x,y);

，效果很好!!!但只是第一次!!!

问题是 如果我关闭我的自定义uiview初始化的主视图控制器并且我回来（例如再次播放）出现此错误

[__ NSCFType addLine：]：发送到实例的无法识别的选择器 0x1454dec0 * 由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因：' - [__ NSCFType addLine：]：无法识别的选择器发送到实例0x1454dec0'

看来观察员在解雇后不再工作......你能帮助我吗？

感谢

Answer 1

您可能忘记删除dealloc中的观察者

- (void)dealloc {

    [[NSNotificationCenter defaultCenter] removeObserver:self];

}

Answer 2

我认为你应该这样试试。

-(void)viewDidLoad
{
//....YOUR_CODE....
//Add Observer
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(addLine:) name:@"addLine" object:nil];
}

//Implement method for the notification
-(void)addLine:(NSNotification *)notification
{
NSDictionary* userInfo = notification.userInfo;
float x = [[userInfo objectForKey:@"x"] floatValue];
float y = [[userInfo objectForKey:@"y"] floatValue];
p = CGPointMake(x,y);
}

//and implement dealloc or viewDidDisappear or viewDidUnload method to remove observer.
- (void)dealloc {
    [[NSNotificationCenter defaultCenter]removeObserver:self name:@"addLine" object:nil];    
}

//In Your Custom view or view controller, post notification as below..
[[NSNotificationCenter defaultCenter] postNotificationName:@"addLine" object:self userInfo:userInfo];

Answer 3

在对象内部的postnotification方法中，你传递的是self，但是在添加观察者时，你传递的是nil。所以修改了以下方法： -

    [[NSNotificationCenter defaultCenter] addObserver:self 
selector:@selector(addLine:) name:@"addLine" object:self];

解除后再出现自定义UIView控制器错误的NSNotificationCenter

3 个答案: