XCode5 使用AutoLayout情况下改变控件的 方法

[self.viewButtonsetTranslatesAutoresizingMaskIntoConstraints:NO];

    //[self.view addConstraint:[NSLayoutConstraint constraintWithItem:self.viewButton attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1 constant:0]];

    //改变 高度

    [self.viewaddConstraint:[NSLayoutConstraint

                              constraintWithItem:self.viewButton

                              attribute:NSLayoutAttributeHeight

                              relatedBy:NSLayoutRelationEqual

                              toItem:self.view

                              attribute:NSLayoutAttributeHeight

                              multiplier:0.3

                              constant:0]];

    [self.viewButtonaddObserver:selfforKeyPath:@"bounds"options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionInitialcontext:nil];//注册kvo监听bounds的变化

    

}

//kvo回调

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context

{

    if (object == self.viewButton && [keyPath isEqualToString:@"bounds"])

    {

//        [self.viewButton setTitle:NSStringFromCGSize(self.viewButton.bounds.size) forState:UIControlStateNormal];

        

        NSLog(@"");

    }

}