參考官方文檔，淺顯提取和理解

參考鏈接

創(chuàng)建navigationBar

- (void)loadView{
    // view= nil會(huì)調(diào)用loadView方法
    // view為nil，在loadView內(nèi)調(diào)用self.view會(huì)造成死循環(huán),導(dǎo)致內(nèi)存泄漏
    self.view = [[UIView alloc] init];
    
    _navigationBar = [[UINavigationBar alloc]init];
    _navigationBar.delegate = self;
    [self.view addSubview:_navigationBar];
}

計(jì)算statuBar到navigationBar的高度

CGFloat topLayoutGuide = 0.0f;
if ([self respondsToSelector:@selector(topLayoutGuide)])
   topLayoutGuide = (self.topLayoutGuide).length;

根據(jù)此設(shè)置navigationBar的frame

[_navigationBar sizeToFit]; // return 'best' size to fit current view bounds
_navigationBar.frame = CGRectMake(_navigationBar.frame.origin.x, topLayoutGuide,_navigationBar.frame.size.width,_navigationBar.frame.size.height);

計(jì)算剩余展示子視圖或子控制器的frame

return CGRectMake(0,
_navigationBar.frame.size.height + _navigationBar.frame.origin.y,
self.view.bounds.size.width,
self.view.bounds.size.height - _navigationBar.frame.size.height - _navigationBar.frame.origin.y);