When the user clicks a

• 当用户单击

When the user clicks a的用法和样例：

例句

1. Control will request child-node data when a user clicks the node.
   控件将在用户单击节点时请求子节点数据。
2. Typically, a user clicks on an object and it becomes selected.
   比如，用户单击一个对象，对象选中。