UIBarButtonItem * item = [UIBarButtonItem appearance];
UIImage* image = [UIImage imageNamed:@"back_icon"];
[item setBackButtonBackgroundImage:[image resizableImageWithCapInsets:UIEdgeInsetsMake(0, image.size.width, 0, 0)] forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
//[item setBackButtonBackgroundVerticalPositionAdjustment:20.f forBarMetrics:UIBarMetricsDefault];
[item setBackButtonTitlePositionAdjustment:UIOffsetMake(0.f, 0) forBarMetrics:UIBarMetricsDefault];iOS 自定义导航栏的返回按钮
原文：http://blog.csdn.net/darongzi1314/article/details/45096457
