Android UsageStatsManager未为时间间隔提供适当的数据

使用

usagestastsmanager

我试图获取从上午12点到当前时间的数据。我编写了以下代码：

        Calendar calendar = Calendar.getInstance();
        calendar.set(Calendar.HOUR_OF_DAY, 0);
        calendar.set(Calendar.MINUTE, 0);
        calendar.set(Calendar.SECOND, 0);

        UsageStatsManager usageStatsManager = (UsageStatsManager) getActivity().getSystemService(Context.USAGE_STATS_SERVICE);
        long endTime = System.currentTimeMillis();
        long beginTime = calendar.getTimeInMillis();

        UsageEvents usageEvents = usageStatsManager.queryEvents(beginTime, endTime);

但提供的结果每4或6小时重置一次；比如早上6点，下午12点，下午4点，凌晨12点。这里怎么了