如下所示，我在不使用NavigationController的情况下设置了NavigationBar高度 （使用导航栏作为独立对象）
UINavigationBar* navbar = [[UINavigationBar alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, 40)];
UINavigationItem* navItem = [[UINavigationItem alloc] initWithTitle:@"title"];
UIBarButtonItem* cancelBtn = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCancel target:self action:@selector(onTapCancel:)];
navItem.leftBarButtonItem = cancelBtn;
UIBarButtonItem* doneBtn = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(onTapDone:)];
navItem.rightBarButtonItem = doneBtn;
[navbar setItems:@[navItem]];
[self.view addSubview:navbar];
但它不适用于iOS11测试版 实际上，NavBar高度看起来总是默认高度= 44 它适用于iOS10之前。
我试过beta7，但没有任何改变 有没有办法设置NavigationBar高度？
除了
我试着像下面的代码那样应用Autolayout Constraint
在这种情况下，＆＃34; leadingAnchor＆＃34;，＆＃34; topAnchor＆＃34;，＆＃34; widthAncohr＆＃34;像我预期的那样工作
但是我无法控制＆＃34; heightAnchor＆＃34;
这是在iOS11 GM版本上试用的。
UINavigationBar* navbar = [[UINavigationBar alloc] init];
navbar.translatesAutoresizingMaskIntoConstraints = false;
UINavigationItem* navItem = [[UINavigationItem alloc] initWithTitle:@"title"];
UIBarButtonItem* cancelBtn = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCancel target:self action:@selector(onTapCancel:)];
navItem.leftBarButtonItem = cancelBtn;
UIBarButtonItem* doneBtn = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(onTapDone:)];
navItem.rightBarButtonItem = doneBtn;
[navbar setItems:@[navItem]];
[self.view addSubview:navbar];
[NSLayoutConstraint activateConstraints:@[[[navbar leadingAnchor] constraintEqualToAnchor:self.view.leadingAnchor constant:0]]];
[NSLayoutConstraint activateConstraints:@[[[navbar topAnchor] constraintEqualToAnchor:self.view.topAnchor constant:50]]];
[NSLayoutConstraint activateConstraints:@[[[navbar heightAnchor] constraintEqualToConstant:100.0]]];
[NSLayoutConstraint activateConstraints:@[[[navbar widthAnchor] constraintEqualToAnchor:self.view.widthAnchor]]];