自定义返回箭头
UIImage *backImage = [[UIImage imageNamed:@"backicon.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
[self.navigationController.navigationBar setBackIndicatorImage:backImage];
[self.navigationController.navigationBar setBackIndicatorTransitionMaskImage:backImage];
距离左侧距离
UIBarButtonItem *leftButon = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"BackButton"] style:UIBarButtonItemStylePlain target:nil action:nil];
```
UIBarButtonItem *fixedButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace target:nil action:nil];
fixedButton.width = -15;
self.navigationItem.leftBarButtonItems = @[fixedButton, leftButon]; 