android P 开机铃声添加将audio.wav 放到bootanimation.zip 中的part0中。
变量 persist.sys.bootanim.play_sound 控制释放播放铃声

具体的代码

具体的实现再bootanimation_main.cpp中

static const char PLAY_SOUND_PROP_NAME[] = "persist.sys.bootanim.play_sound";
static const char BOOT_COMPLETED_PROP_NAME[] = "sys.boot_completed";
static const char POWER_CTL_PROP_NAME[] = "sys.powerctl";
static const char BOOTREASON_PROP_NAME[] = "ro.boot.bootreason";


bool playSoundsAllowed() {
    // Only play sounds for system boots, not runtime restarts.
    if (android::base::GetBoolProperty(BOOT_COMPLETED_PROP_NAME, false)) {
        return false;
    }
    // no audio while shutting down
    if (!android::base::GetProperty(POWER_CTL_PROP_NAME, "").empty()) {
        return false;
    }
    // Read the system property to see if we should play the sound.
    // If it's not present, default to allowed.
    if (!property_get_bool(PLAY_SOUND_PROP_NAME, 1)) {
        return false;
    }

    // Don't play sounds if this is a reboot due to an error.
    char bootreason[PROPERTY_VALUE_MAX];
    if (property_get(BOOTREASON_PROP_NAME, bootreason, nullptr) > 0) {
        for (const auto& str : PLAY_SOUND_BOOTREASON_BLACKLIST) {
            if (strcasecmp(str.c_str(), bootreason) == 0) {
                return false;
            }
        }
    }
    return true;
}



void playPart(int partNumber, const Animation::Part& part, int playNumber) override {
    // only play audio file the first time we animate the part
    if (playNumber == 0 && part.audioData && playSoundsAllowed()) {
        ALOGD("playing clip for part%d, size=%d",
              partNumber, part.audioLength);
        // Block until the audio engine is finished initializing.
        if (initAudioThread != nullptr) {
            initAudioThread->join();
        }
        audioplay::playClip(part.audioData, part.audioLength);
    }
};