iOS 11 backBarButtonItem重复

Question

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在我们在iOS 11中测试我们的应用程序之前它工作正常.`UIImage * imageNor = [UIImage imageNamed：@“nav_icon_back_nor1”];     UIImage * imagePre = [UIImage imageNamed：@“nav_icon_back_pre1”];     UIBarButtonItem * item = [[UIBarButtonItem alloc] init];     [item setBackButtonBackgroundImage：[imageNor resizableImageWithCapInsets：UIEdgeInsetsMake（0，imageNor.size.width，0,0）] forState：UIControlStateNormal barMetrics：UIBarMetricsDefault];     [item setBackButtonBackgroundImage：[imagePre resizableImageWithCapInsets：UIEdgeInsetsMake（0，imagePre.size.width，0,0）] forState：UIControlStateHighlighted barMetrics：UIBarMetricsDefault];     [item setBackButtonTitlePositionAdjustment：UIOffsetMake（-400.f，0）forBarMetrics：UIBarMetricsDefault];     [item setTitle：@“”];

self.navigationItem.backBarButtonItem = item;`