android 显示系统时间

private void updateTime() {
    long uptime = SystemClock.elapsedRealtime();
    Log.v(TAG, "updateTime uptime = " + uptime);
    String time = DateUtils.formatElapsedTime(uptime / 1000);
    Log.v(TAG, "updateTime time = " + time);
    mUptime.setSummary(time);
}