Android L获取前台应用的包名

背景

前一段时间发现android5.0以后的手机发现我们的APP悬浮窗获取前台应用的名称不起作用了，以前我们的作法如下：

public String getForegroundApp(Context context) {      ActivityManager am = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);      List<RunningAppProcesInfo> lr = am.getRunningAppProcesses();      if (lr == null) {            return null;      }      for (RunningAppProcessInfo ra : lr) {          if (ra.importance == RunningAppProcessInfo.IMPORTANCE_VISIBLE               || ra.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {                      return ra.processName;         }      }        return null;  }

private String getForegroundApp() {          long ts = System.currentTimeMillis();          List<UsageStats> queryUsageStats = usageStatsManager.queryUsageStats(UsageStatsManager.INTERVAL_BEST,ts-2000, ts);          if (queryUsageStats == null || queryUsageStats.isEmpty()) {                  return null;          }          UsageStats recentStats = null;          for (UsageStats usageStats : queryUsageStats) {                  if(recentStats == null || recentStats.getLastTimeUsed() < usageStats.getLastTimeUsed()){                          recentStats = usageStats;                  }          }          return recentStats.getPackageName;  }