(1)在设置navigationItem的leftBarButtonItem或者rightBarButtonItem的时候,发现大小不起效果

UIButton *shareButton = [UIButton buttonWithType: (UIButtonTypeCustom)];  
shareButton.frame = CGRectMake(0, 0, 30, 30);  
 shareButton.backgroundColor = [UIColor blueColor];  
 [shareButton setImage:[UIImage imageNamed:@"mv_actionIconSaveToAlbum"]  forState:(UIControlStateNormal)];  
 UIBarButtonItem *rightBtnItem = [[UIBarButtonItem alloc] initWithCustomView:shareButton];  
 self.navigationItem.rightBarButtonItem = rightBtnItem;  

• 如果图片大小大于按钮,这个时候设置按钮的frame是不会起作用的,所以需要先将图片缩放,然后再放进button 里面就好了