ALSA音量变化回调未触发

Question

我有一个函数，我设置为回调，但事件正在发生，该函数没有被调用。还有什么我需要做的吗?

// static
int volume_change_callback(snd_mixer_elem_t* elem,
                                              unsigned int mask) {
  // Do stuff
}

snd_mixer_elem_set_callback(element, volume_change_callback); 

Answer 1

您需要使用snd_mixer_handle_events()来实际调用回调。(http://www.alsa-project.org/alsa-doc/alsa-lib/group___mixer.html gae0cfb6b50ec2493281107b0649f87cb8)

查看mixer.c (https://fossies.org/dox/alsa-utils-1.0.29/amixer_8c_source.html)以获取处理事件的示例:

  while (1) {
      int res;
      res = snd_mixer_wait(handle, -1);
      if (res >= 0) {
          printf("Poll ok: %in", res);
          res = snd_mixer_handle_events(handle);
          assert(res >= 0);
      }
  }