CoreMediaIO，错误地更新了属性kCMIODevicePropertyDeviceIsRunningSomewhere [英] CoreMediaIO, incorrectly updated properties kCMIODevicePropertyDeviceIsRunningSomewhere

问题描述

当某些过程开始使用相机时，我需要接收一个事件.我通过CMIOObjectGetPropertyData做到了这一点.但是它不能正常工作，正确的值只是第一次访问它.

I need to receive an event when some process starts using the camera. I did this through CMIOObjectGetPropertyData. But it does not work correctly, the correct value is only the first time it is accessed.

我也尝试使用CMIOObjectAddPropertyListenerBlock，但是他没有从我这里使用它.请告诉我，我做错了什么?我将非常感谢.

I also tried to use the CMIOObjectAddPropertyListenerBlock but he did not work it from me. Tell me please, what am I doing wrong? I will be very grateful.

while (1)
{
    UInt32 value = 0;
    UInt32 valuePropertySize = sizeof(flag);
    CMIOObjectPropertyAddress opa = {kCMIODevicePropertyDeviceIsRunningSomewhere,
        kAudioObjectPropertyScopeWildcard, kAudioObjectPropertyElementMaster};

    OSStatus result = CMIOObjectGetPropertyData(device, &opa, 0, NULL, sizeof(UInt32), &valuePropertySize, &value);
    NSLog(@"%d : %d", result, value);
    sleep(1);
}

推荐答案

我也遇到了同样的问题.使用 CMIOObjectGetPropertyData 获取数据是可行的，但是使用 CMIOObjectAddPropertyListenerBlock 注册侦听器块从未收到任何事件.

I also had the same problem. Getting data with CMIOObjectGetPropertyData worked but registering a listener block with CMIOObjectAddPropertyListenerBlock never received any event.

该问题的解决方案与CMIO *代码完全无关.基本上，我忘了开始运行循环，这阻止了接收事件.

The solution to the issue was totally unrelated to the CMIO* code. Basically, I forgot to start the run loop, and that prevented receiving events.

请在此处查看: currentRunLoop

添加一个简单的 [[NSRunLoop currentRunLoop]运行]; 为我解决了此问题

Adding a simple [[NSRunLoop currentRunLoop] run]; fixed the issue for me

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