返回一个接收者是否是第一响应者的标识（布尔值）。
Returns a Boolean value indicating whether the receiver is the first responder.
任何输入都是由第一响应者先捕捉到的，它一般是与用户直接交互的对象。
Any input is captured by the first responder, which tends to be the object that the user is directly interacting with.
报告接受者它将要在window 上成为为第一响应者。 默认返回 YES。
Notifies the receiver that it is about to become first responder in its window.
我们在工作能力和设备上投入了很多，同时提高了作为第一响应者的通信系统的协同性和可靠性。
We are investing inoperational capabilities and equipment, and improving the reliability andinteroperability of communications systems for first responders.
我们在工作能力和设备上投入了很多，同时提高了作为第一响应者的通信系统的协同性和可靠性。
We are investing inoperational capabilities and equipment, and improving the reliability andinteroperability of communications systems for first responders.
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