调整navigationItem的位置

UIBarButtonItem *itemTransformView = [[UIBarButtonItem alloc] initWithCustomView:_header.transformView];

// 调整 leftBarButtonItem 在 iOS7 下面的位置

if(([[[UIDevice currentDevice] systemVersion] floatValue]>=7.0)){

UIBarButtonItem *negativeSpacer = [[UIBarButtonItem alloc]

initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace

target:nil action:nil];

negativeSpacer.width = -12;

self.navigationItem.rightBarButtonItems = @[negativeSpacer, itemTransformView];

}else{

self.navigationItem.rightBarButtonItem = itemTransformView;

}