iOS-UINavgationBar backItemiOS7以后靠右问题

UIButton * backButton = [UIButton buttonWithType:UIButtonTypeCustom];

backButton.frame = CGRectMake(0, 0, 60, 44);

[backButton setImage:[UIImage imageNamed:@"back_btn_bg.png"] forState:UIControlStateNormal];

[backButton setTitle:@"Back"forState:UIControlStateNormal];

[backButton setTitleEdgeInsets:UIEdgeInsetsMake(-1, -55, 0, 0)];

[backButton.titleLabel setFont:[UIFont boldSystemFontOfSize:14.0]];

[backButton setTitleColor:[UIColor colorWithRed:233.0/255.0 green:220.0/255.0 blue:207.0/255.0 alpha:1.0]

forState:UIControlStateNormal];

UIBarButtonItem *backNavigationItem = [[UIBarButtonItem alloc] initWithCustomView:backButton];

// 调整 leftBarButtonItem 在 iOS7 下面的位置

if(([[[UIDevice currentDevice] systemVersion] floatValue]>=7.0?20:0)){

UIBarButtonItem *negativeSpacer = [[UIBarButtonItem alloc]

initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace

target:nilaction:nil];

negativeSpacer.width = -10;

self.navigationItem.leftBarButtonItems = @[negativeSpacer, backNavigationItem];

}else

self.navigationItem.leftBarButtonItem = backNavigationItem;