在子级中创建一个新事件并在父级中订阅它(实例化该子级之后).

在子项中的按钮单击处理程序中，引发新事件.在父级的新事件处理程序中，聚焦所需的按钮.

Create a new event in the child and subscribe to it in the parent (after instanciating the child).

In the button''s click handler in the child, raise the new event. In the new event''s handler in the parent, Focus the required button.