[Android Pro] How to get recent tasks on Android “L”?

reference : http://stackoverflow.com/questions/24590533/how-to-get-recent-tasks-on-android-l/26885469#26885469

<uses-permission android:name="android.permission.PACKAGE_USAGE_STATS" />

String topPackageName ;
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
    UsageStatsManager mUsageStatsManager = (UsageStatsManager)getSystemService("usagestats");
    long time = System.currentTimeMillis();
    // We get usage stats for the last 10 seconds
    List<UsageStats> stats = mUsageStatsManager.queryUsageStats(UsageStatsManager.INTERVAL_DAILY, time - 1000*10, time);
    // Sort the stats by the last time used
    if(stats != null) {
        SortedMap<Long,UsageStats> mySortedMap = new TreeMap<Long,UsageStats>();
        for (UsageStats usageStats : stats) {
            mySortedMap.put(usageStats.getLastTimeUsed(),usageStats);
        }
        if(mySortedMap != null && !mySortedMap.isEmpty()) {
            topPackageName =  mySortedMap.get(mySortedMap.lastKey()).getPackageName();
        }
    }
}