原因:ヌルポ
===
public void ring() {
if (ring_tone == null) {
Uri ringtone = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_RINGTONE);
ring_tone = RingtoneManager.getRingtone(waffle_activity, ringtone);
}
if (ring_tone.isPlaying()) return;
ring_tone.play();
}
===