UIBarButton 图片显示不正常解决方案

在storyboard上set image会显示成蓝色的形状，查过资料说应该设置图片的alpha值，还TND设置个鬼的alpha，从stackOverFlow找到了解决方法，很简单，具体思路是：

1. 构建一个带背景的UIButton

2. 把构建的UIButton用UIBarButton初始化

具体代码：

//设置UIButton
UIImage *menuImage = [UIImage imageNamed:@"navBarMenuButton.png"];
UIButton *leftButton = [UIButton buttonWithType:UIButtonTypeCustom];
leftButton.frame = CGRectMake(0, 0, menuImage.size.width, menuImage.size.height);
[leftButton setBackgroundImage:menuImage forState:UIControlStateNormal];
//以UIBarButton初始化
aController.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:leftButton];