回调函数(如果不需要回调，就是null)。

Callback function (null if no callback is needed).

youdao

另外，通常还需要回调方法和发布与订阅方法。

Also, there's often a need for callback methods as well as publish and subscribe methods.

youdao

要使用需要回调函数的dll函数，则会有一些附加的步骤。

Using a DLL function that requires a callback function has some additional steps.

youdao