-(void) viewWillAppear:(BOOL)animated {
    
    //注册键盘出现通知
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector (keyboardDidshow:)
                                                 name: UIKeyboardDidShowNotification object:nil];
    //注册键盘隐藏通知
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector (keyboardDidHide:)
                                                 name: UIKeyboardDidHideNotification object:nil];
    [super viewWillAppear:animated];
}


-(void) viewWillDisappear:(BOOL)animated {
    //解除键盘出现通知
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name: UIKeyboardDidShowNotification object:nil];
    //解除键盘隐藏通知
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name: UIKeyboardDidHideNotification object:nil];
    
    [super viewWillDisappear:animated];
}
-(void) keyboardDidshow: (NSNotification *)notif {
    if (keyboardVisible) {
        return; // 键盘出现时，忽略通知
    }
    
    // 获得键盘尺寸
    NSDictionary *info = [notif userInfo];
    NSValue *aValue = http://www.mamicode.com/[info objectForKey:UIKeyboardFrameEndUserInfoKey];>
键盘滚动到当前文本框和按return隐藏