我正在使用 ng-bootstrap 和 Angular 7 创建一个标准的引导菜单，右侧有链接，但如果我使用下拉菜单，它会退出屏幕。为了确保我没有弄乱代码，我干净地安装了 angular、bootstrap（只是 angular.json 中的 css 代码）和 ng-bootstrap。我已经在 AppModule 中包含了 NgbModule 并尝试了以下代码：
<nav class="navbar navbar-expand-lg navbar-light bg-light">
<a class="navbar-brand" href="#">Navbar</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav ml-auto">
<li class="nav-item active">
<a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Link</a>
</li>
<li class="nav-item dropdown" ngbDropdown placement="bottom-right">
<a class="nav-link dropdown-toggle" ngbDropdownToggle href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown
</a>
<div class="dropdown-menu" ngbDropdownMenu aria-labelledby="navbarDropdown">
<a …