解决 ios7.0 以后自定义导航栏左边按钮靠右的问题

  UIButton *backButton = [[UIButton
alloc] initWithFrame:CGRectMake(0,
0, 30,30)];
    [backButton setTitleEdgeInsets:UIEdgeInsetsMake(-10.0,
0.0, 0.0,
0.0)];

    [backButton setImage:[UIImage
imageNamed:@"back_icon"]
forState:UIControlStateNormal];
    [backButton addTarget:self.navigationController
action:@selector(popViewControllerAnimated:)
forControlEvents:UIControlEventTouchUpInside];
    UIBarButtonItem *backItem = [[UIBarButtonItem
alloc] initWithCustomView:backButton];
//    [self.navigationItem setLeftBarButtonItem:backItem];
  
    UIBarButtonItem *negativeSpacer = [[UIBarButtonItem
alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace
                                                                                  
target:nil
action:nil];
    negativeSpacer.width = -10;//这个数值可以根据情况自由变化
    self.navigationItem.leftBarButtonItems =
@[negativeSpacer,backItem];