XCode9解决导航栏按钮图片变形拉伸

不要直接加按钮

先变成UIView+视图

UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 44, 44)];

[view addSubview:headBtn];

self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]initWithCustomView:view];