定制navgation上的按钮，设置自己的风格的UIBarButtonItem

 UIImage* image= [UIImage imageNamed:@"绑定弹出－返回.png"];
         CGRect frame_1= CGRectMake(0, 0, image.size.width, image.size.height-4);
         UIButton* backButton= [[UIButton alloc] initWithFrame:frame_1];
         [backButton setBackgroundImage:image forState:UIControlStateNormal];
         [backButton setTitle:@"返回" forState:UIControlStateNormal];
         [backButton setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
         backButton.titleLabel.font=[UIFont systemFontOfSize:16];
         [backButton addTarget:self action:@selector(doBack:) forControlEvents:UIControlEventTouchUpInside];

 //定制自己的风格的 UIBarButtonItem
 UIBarButtonItem* someBarButtonItem= [[UIBarButtonItem alloc] initWithCustomView:backButton];
         [self.navigationItem setLeftBarButtonItem:someBarButtonItem];
         [someBarButtonItem release];
         [backButton release];