通常通过以下方法监听键盘事件
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardChange:) name:UIKeyboardWillChangeFrameNotification object:nil];
- (void)keyboardChange:(NSNotification*)aNotification{
NSDictionary* userInfo = [aNotification userInfo];
NSTimeInterval animationDuration = [[userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
UIViewAnimationCurve animationCurve = [[userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] intValue];
CGRect keyboardEndFrame = [[userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
CGFloat keyboardY = keyboardEndFrame.origin.y;
CGFloat height = SCREEN_HEIGHT-keyboardY;
BOOL show;
if (ABS(height)>0.1) {
//show
show = YES;
}else{
//hide
show = NO;
}
