Is it possible to detect and respond to the answer/end-call button presses from an HFP Bluetooth device on iOS? Has anyone seen this? Where should I look for answers? I understand one could get access to lower level bluetooth if you register for the device manufacturer (MFI) program but I'm hoping I don't have to dive this deep. I also know that you can respond to AVRCP commands but I am not wanting to use this option. Can anyone help?
UIResponder has a -remoteControlReceivedWithEvent: method that you can use to receive events from external devices, possibly including Bluetooth headsets. From the docs:
Remote-control events originate as commands from external accessories, including headsets. An application responds to these commands by controlling audio or video media presented to the user. The receiving responder object should examine the subtype of event to determine the intended command—for example, play (UIEventSubtypeRemoteControlPlay)—and then proceed accordingly.
To allow delivery of remote-control events, you must call the beginReceivingRemoteControlEvents method of UIApplication; to turn off delivery of remote-control events, call endReceivingRemoteControlEvents.
It’s not clear whether the answer/end button on a headset is considered equivalent to the play/pause button on, say, the earbuds’ remote, but this might be worth a try.
Sadly, there are no available bluetooth public APIs for developers, so no way to get that access in the conventional means.
As of my research, some person received some event from their bleu-tooth devices via "remoteControlReceivedWithEvent" but not all of them! Some are receiving none! And very few are receiving all of them!
I also tried Core Bluetooth but it only supports LEB (Low Energy Bluetooth devices)! https://developer.apple.com/library/ios/documentation/NetworkingInternetWeb/Conceptual/CoreBluetooth_concepts/CoreBluetoothOverview/CoreBluetoothOverview.html#//apple_ref/doc/uid/TP40013257-CH2-SW1
Also, some posts suggest it is possible to use Classic bleutooth instead of "Low Energy": How to use bluetooth classic instead of le But it has limitation as well (the post is taking about "MFi accessory"! MFi is it for "made for iphone" ?!?!?!)
from the post above: "A non-LE Bluetooth device needs to be MFi-approved to be used with the External Accessory framework (it needs to use a specific Apple chip and a proprietary communication protocol). You won't be able to build applications to access this device unless it either uses the more open Bluetooth LE or has this chip in it for standard Bluetooth. There might be ways to do this via jailbreak, but pretty much everyone I know has moved over to Bluetooth LE." !
more post: Connecting to a Bluetooth device from iOS, no MFi
Regards.
来源：https://stackoverflow.com/questions/7210182/detect-bluetooth-answer-end-call-button-on-iphone