Android

public class MainActivity extends AppCompatActivity
{
    private int position;
    private int value;
    private Button button;
    private EditText editText;
    private TextView textView1,textView2;
    private Spinner spinner,spinner2;
    private ArrayAdapter<CharSequence> adapter;

    private boolean isValid;
    private Date date;
    private int inMonth, inDay, inYear;

    static boolean isDateValid(int month, int day, int year)
    {
        boolean validation = true;
        int[] daysInMonth = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

        if (month < 1 || month > 12)
        {
            validation = false;
        }

        if (day < 1 || day > daysInMonth[month - 1])
        {
            validation = false;
        }

        if (year < 1700 || year > 3000)
        {
            validation = false;
        }
        return validation;
    }

    static String zellerCalc(int month, int day, int year)
    {
        String dayOfWeek;
        int m = -1; 
        int h = -1; 
        int q = day;
        int k;
        int j;

        if (month == 1)
        {
            m = 13;
        }
        else if (month == 2)
        {
            m = 14;
        }
        else
        {
            m = month;
        }

        if (m == 13 || m == 14)
        {
            year--;
        }

        k = year % 100;
        j = year / 100; 

        h = (q + (int)((13 * (m + 1)) / 5.0) + k + (int)(k / 4.0) + (int)(j / 4.0) + (5 * j)) % 7;

        if (h == 0)
        {
            dayOfWeek = "Subota";
        }
        else if (h == 1)
        {
            dayOfWeek = "Nedelja";
        }
        else if (h == 2)
        {
            dayOfWeek = "Ponedeljak";
        }
        else if (h == 3)
        {
            dayOfWeek = "Utorak";
        }
        else if (h == 4)
        {
            dayOfWeek = "Sreda";
        }
        else if (h == 5)
        {
            dayOfWeek = "Četvrtak";
        }
        else
            dayOfWeek = "Petak";

        return dayOfWeek;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        button = (Button) findViewById(R.id.button_calculate);
        textView1 = (TextView) findViewById(R.id.textView_day);
        textView2 = (TextView) findViewById(R.id.textView_year);
        spinner = (Spinner) findViewById(R.id.spinner_month);
        spinner2 = (Spinner) findViewById(R.id.spinner_day);
        editText = (EditText) findViewById(R.id.editText_year);

        adapter = ArrayAdapter.createFromResource(this,R.array.months,android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(adapter);

        adapter = ArrayAdapter.createFromResource(this,R.array.day,android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner2.setAdapter(adapter);

        if (spinner2.getSelectedItemPosition() == 0)
            value = 1;
        if (spinner2.getSelectedItemPosition() == 1)
            value = 2;
        if (spinner2.getSelectedItemPosition() == 2)
            value = 3;
        if (spinner2.getSelectedItemPosition() == 3)
            value = 4;
        if (spinner2.getSelectedItemPosition() == 4)
            value = 5;
        if (spinner2.getSelectedItemPosition() == 5)
            value = 6;
        if (spinner2.getSelectedItemPosition() == 6)
            value = 7;
        if (spinner2.getSelectedItemPosition() == 7)
            value = 8;
        if (spinner2.getSelectedItemPosition() == 8)
            value = 9;
        if (spinner2.getSelectedItemPosition() == 9)
            value = 10;
        if (spinner2.getSelectedItemPosition() == 10)
            value = 11;
        if (spinner2.getSelectedItemPosition() == 11)
            value = 12;

        button.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View view)
            {
                String dayOfWeek;
                boolean isValid;

                Calendar c = Calendar.getInstance();
                SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd_HHmmss");
                String strDate = sdf.format(c.getTime());
            do
            {
                try
                {
                    String getdate = spinner.getItemAtPosition(position).toString() + value
                            + textView2.getText().toString();
                    Date date = sdf.parse(getdate);
                }
                catch (ParseException ex)
                {

                }

                isValid = isDateValid(date.getMonth(), date.getDay(), date.getYear());

                if (isValid == false)
                {
                   Toast.makeText(MainActivity.this,"You entered wrong date",Toast.LENGTH_SHORT).show();
                }
            }
            while (isValid == false);

                dayOfWeek = zellerCalc(date.getMonth(), date.getDay(), date.getYear());

                textView1.setText(dayOfWeek);
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        int id = item.getItemId();

        if (id == R.id.action_settings)
        {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

public class MainActivity extends AppCompatActivity
{

    public void startOtgService()
    {
        startService(new Intent(MainActivity.this, OtgService.class));

    }

    public void stopOtgService()
    {
        stopService(new Intent(MainActivity.this, OtgService.class));

    }

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View view)
            {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        Button startButton = (Button)this.findViewById(R.id.startButton);
        Button stopButton = (Button)this.findViewById(R.id.stopButton);

        startButton.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                startOtgService();
            }
        });

        stopButton.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                stopOtgService();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);

        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings)
        {
            return true;
        }
        if(id ==  R.id.action_cable)
        {

        }
        return super.onOptionsItemSelected(item);
    }
}

public class OtgService extends Service
{

    private boolean mOtgConnected = false;
    private Handler mHandler;

    Timer taskTimer = new Timer();

    TimerTask task = new TimerTask()
    {
        private int last_Length = -1;

        @Override
        public void run()
        {
            Context context = OtgService.this.getBaseContext();

            File directory = new File("/sys/bus/usb/devices");
            File[] contents = directory.listFiles();

            int conn_length = contents.length;

            if(conn_length ==last_Length)
            {
                return;
            }
            else
            {
                last_Length = conn_length;
            }

            if(conn_length == 0)
            {
                mOtgConnected = false;
                mHandler.post(flagChangedTask);
            }
            else if (conn_length > 0)  //Might get a -1
            {
                mOtgConnected = true;
                mHandler.post(flagChangedTask);

            }

        }
    };

    Runnable flagChangedTask = new Runnable()
    {
        @Override
        public void run()
        {
            if (mOtgConnected)
                Toast.makeText(OtgService.this,"otg connected",Toast.LENGTH_SHORT).show();
            else
                Toast.makeText(OtgService.this,"otg not connected",Toast.LENGTH_SHORT).show();
        }
    };


    public OtgService()
    {

    }


    private void onStartCompat(Intent intent)
    {
        Log.e("###", "Starting service!");

        if (mHandler == null)
            mHandler = new Handler(getMainLooper());

        taskTimer.scheduleAtFixedRate(task, 0, 1000);
    }

    @Override
    public void onStart(Intent intent, int startId)
    {
        onStartCompat(intent);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId)
    {
        onStartCompat(intent);
        return START_STICKY;
    }

    @Override
    public void onDestroy()
    {
        //task.cancel();
    }


    @Override
    public IBinder onBind(Intent intent)
    {
        return null;
    }
}

public interface RequestPermissionsResultInterface
{
  void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults);
}

public interface PermissionManagerInterface
{
  void onPermissionGranted(String message, int requestCode);
  void onPermissionDenied(String message, int requestCode);
}

public class PermissionManager implements RequestPermissionsResultInterface
{
    private Activity mActivity;
    private static Context mContext;
    private static PermissionManager mPermissionManager;
    private static volatile PermissionManagerInterface mManagerInterface;

    
    public static PermissionManager getInstance(Context context)
    {
        if (mPermissionManager == null)
        {
            synchronized (PermissionManager.class)
            {
                if (mPermissionManager == null)
                {
                    mPermissionManager = new PermissionManager(context);
                }
            }
        }
        return mPermissionManager;
    }

    public PermissionManager(Context context) {
        mContext = context;
    }

    public RequestPermissionsResultInterface askPermission(
            Activity mActivity,
            String permissionName,
            final PermissionManagerInterface managerInterface,
            final int requestCode)
    {
       if (ContextCompat.checkSelfPermission(mActivity, permissionName) != PackageManager.PERMISSION_GRANTED)
       {
          // show message box
       }
       else
          ActivityCompat.requestPermissions(
                      mActivity,
                      new String[]{permissionName},
                      requestCode);
    }

  @Override
  public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults)
  {
    if(grantResults[0] == PackageManager.PERMISSION_GRANTED)
      mManagerInterface.onPermissionGranted("Permission Granted", requestCode);
    else
      mManagerInterface.onPermissionDenied("Permission Denied", requestCode);
  }
}

mPermissionManagerInterface = new PermissionManagerInterface() {
    @Override
    public void onPermissionGranted(String message, int requestCode)
    {
        Toast.makeText(MainActivity.this, message, Toast.LENGTH_SHORT).show();
    }
    @Override
    public void onPermissionDenied(String message, int requestCode)
    {
        Toast.makeText(MainActivity.this, message, Toast.LENGTH_SHORT).show();
    }
};

mPermissionManager = PermissionManager.getInstance(this);
mPermissionManager.askPermission(
        this,
        Manifest.permission.READ_EXTERNAL_STORAGE,
        mPermissionManagerInterface,
        EXTERNAL_STORAGE_PERMISSION_CODE);

public class MainActivity extends AppCompatActivity
{
    private Process suProcess;
    private PendingIntent pendingIntent;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        getRoot();
        startAlarm();  
    }

    private void getRoot()
    {
        try
        {
            suProcess = Runtime.getRuntime().exec("su");
        }
        catch (IOException e)
        {

        }
    }

    private void startAlarm()
    {
        Intent alarmIntent = new Intent(MainActivity.this, AlarmReceiver.class);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, alarmIntent, 0);

        AlarmManager manager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        int interval = 1000;
        manager.setInexactRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), interval, pendingIntent);
    }
}

public class AlarmReceiver extends BroadcastReceiver
{
    @Override
    public void onReceive(Context context,Intent intent)
    {
        File[] listFiles = new File("/sys/bus/usb/devices").listFiles();
        if (listFiles == null) Toast.makeText(context,"otg not connected",Toast.LENGTH_SHORT).show();
        if (listFiles != null) Toast.makeText(context,"otg connected",Toast.LENGTH_SHORT).show();
    }
}