如果该焦点所有者未和调用线程处于同一个上下文中，那么该方法会返回空。
This method will return null if the focus owner is not in the same context as the calling thread.
仅当输入读取之间的获得焦点的应用程序是同一个应用程序时，才会到达逻辑块。
The logic block is only reached if the focused application is the same between input reads.
这也解释了为什么缪晓春要把焦点聚集在H 2 O上，因为他认为水是最能体现同一性和连续性的自然元素了。
This also explains why Miao Xiaochun focuses on H2O, a natural element which he believes best embodies these two concepts.
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