Implement foreground app detection using UsageStatsManager

[wizche]

So it supports Android 7/8, similarly to how MisteryBot / ExoBot do (source: https://www.threatfabric.com/blogs/mysterybot__a_new_android_banking_trojan_ready_for_android_7_and_8.html)

@TargetApi(value = 21) 
public void getLastUsedApplication() { 
    try { 
        do { 
            label_0: 
            TimeUnit.MILLISECONDS.sleep(1000); 
            gotolabel_8; 
        } while (true); 
    } catch (InterruptedException interruptedException) { 
        try { 
            interruptedException.printStackTrace(); 
            label_8: 
            Object usageStatsManager = this.getSystemService("usagestats"); 
            long epochTime = System.currentTimeMillis(); 
            List usageStatsList = ((UsageStatsManager) usageStatsManager).queryUsageStats(0, epochTime - 10000, epochTime); 
            if (usageStatsList == null || usageStatsList.size() <= 0) { 
                gotolabel_0; 
            }
            TreeMap sortedMap = new TreeMap(); 
            Iterator usageStatsListIterator = usageStatsList.iterator(); 
            while (usageStatsListIterator.hasNext()) { 
                Object usageStats = usageStatsListIterator.next(); 
                ((SortedMap) sortedMap).put(Long.valueOf(((UsageStats) usageStats).getLastTimeUsed()), usageStats); 
            }

            if (((SortedMap) sortedMap).isEmpty()) { 
                gotolabel_0; 
            }

            String packageName = ((SortedMap) sortedMap).get(((SortedMap) sortedMap).lastKey()).getPackageName(); 
            PrintStream printStream = System.out; 
            StringBuilder output = new StringBuilder().insert(0, "Total:================ ")); 
            output.append(packageName); 
            printStream.println(output.toString()); 
            gotolabel_0; 
        } catch (Exception ex) { 
            ex.printStackTrace(); 
            return; 
        } 
    }
}