iOS Objective-C 在 VoiceOver 处于活动状态时关闭接近监控

Question

I would like to disable Proximity Monitoring, so that screen remains always ON, not matter how close something is to the sensor.

I tried it by using:

UIDevice.currentDevice.proximityMonitoringEnabled = NO;

Normally it is working as expected, however if I turn on VoiceOver, screen begins to black out if proximity sensor is covered.

FYI: I am making Video Call app (using CallKit) for people with low vision, and what they experience is that if they lean too close to the screen during a call, screen blacks out if VoiceOver is on.

I tried installing an NSTimer to set proximityMonitoringEnabled to NO every second (as a poor workaround), also tried setting it YES and then NO. It remains on NO, but screen still blacks out.

Answer 1

In VoIP apps using Apple CallKit (like yours), you can enable and disable proximity monitoring during the call using AVAudioSession() class. It's a known feature when a proximity sensor is triggered and a screen is dimmed while approaching user's face.

By default (if you're not using CallKit) proximityMonitoringEnabled instance property is OFF .

@property(nonatomic, getter=isProximityMonitoringEnabled) BOOL proximityMonitoringEnabled;

// or

UIDevice.currentDevice.proximityMonitoringEnabled = NO;     // DEFAULT VALUE

Apple's developer documentation says:

Enable proximity monitoring only when your application needs to be notified of changes to the proximity state. Otherwise, disable proximity monitoring. The default value is NO .

However, if you use CallKit module, proximityMonitoringEnabled is not behaving as expected. By default a proximity monitoring is enabled – your app use for that a AVAudioSessionModeVoiceChat global variable:

const AVAudioSessionMode AVAudioSessionModeVoiceChat;       // DEFAULT VALUE

Here's what developer documentation says here:

If an app uses the Voice-Processing I/O audio unit and has not set its mode to one of the chat modes (voice, video, or game), AVAudioSessionModeVoiceChat mode will be set implicitly .

Disabling proximity monitoring in CallKit :

Hence, if you want to disable a proximity monitoring just use a AVAudioSessionModeVideoChat global variable :

const AVAudioSessionMode AVAudioSessionModeVideoChat;

Both variables work along with AVAudioSessionCategoryPlayAndRecord global variable:

const AVAudioSessionCategory AVAudioSessionCategoryPlayAndRecord;

Answer 2

I think you have to change the session from AVAudioSessionModeVoiceChat to AVAudioSessionModeVideoChat . Then the proximity sensor should get ignored

Something like that should do:

[[AVAudioSession sharedInstance] setMode: AVAudioSessionModeVideoChat error:&err];