如何使我的ngDropdown菜单在悬停状态而不是单击状态下工作？

import { NgModule } from '@angular/core';
import { NgDropdownModule } from 'ng-dropdown';

@NgModule({
  imports: [
    NgDropdownModule
  ],
  ...
})
export class YourModule { }

<div ngDropdown [trigger]="'hover'">
  <button ngDropdownToggle>Toggle Dropdown</button>
  <ul ngDropdownMenu>
    <li ngDropdownItem>Item 1</li>
    <li ngDropdownItem>Item 2</li>
    <li ngDropdownItem>Item 3</li>
  </ul>
</div>

<div ngDropdown [trigger]="'hover'" [ngDropdownPlacement]="'bottom-right'" [ngDropdownAnimation]="'fade'">
  ...
</div>