NSNotificationCenter 例子

http://hi.baidu.com/%B0%AE%C9%FA%BB%EE%B0%AEqt/blog/item/8136f2d34838352a9b502799.html

1。注册一个通知，当收到“ shake”的时候，触发eraseView这个函数

// Erase the view when recieving a notification named "shake" from the NSNotificationCenter object

// The "shake" nofification is posted by the PaintingWindow object when user shakes the device

[[NSNotificationCenter defaultCenter] addObserver:self                                                                  selector:@selector(eraseView)

                                             name:@"shake"

                                           object:nil];

2。eraseView函数实现

// Called when receiving the "shake" notification; plays the erase sound and redraws the view

-(void) eraseView

{

if(CFAbsoluteTimeGetCurrent() > lastTime + kMinEraseInterval) {

[erasingSound play];

[drawingView erase];

lastTime = CFAbsoluteTimeGetCurrent();

}

}

3。用户触发s事件，发送通知

- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event

{

if (motion == UIEventSubtypeMotionShake )

{

            // User was shaking the device. Post a notification named "shake".

       [[NSNotificationCenter defaultCenter] postNotificationName:@"shake" 

                                            object:self];

}

}