LCD12864 menu structure

#include "U8glib.h"

// setup u8g object, please remove comment from one of the following constructor calls
// IMPORTANT NOTE: The complete list of supported devices is here: http://code.google.com/p/u8glib/wiki/device
  U8GLIB_NHD_C12864 u8g(13, 11, 10, 9, 8);


#define KEY_NONE 0
#define KEY_PREV 1
#define KEY_NEXT 2
#define KEY_SELECT 3
#define KEY_BACK 4

/* DOGS102 shield configuration values
uint8_t uiKeyPrev = 2;
uint8_t uiKeyNext = 4;
uint8_t uiKeySelect = 5;
uint8_t uiKeyBack = 3;
*/
/* DOGM128-Shield   configuration values
// DOGXL60-Shield configuration values
uint8_t uiKeyPrev = 7;
uint8_t uiKeyNext = 3;
uint8_t uiKeySelect = 2;
uint8_t uiKeyBack = 8;
*/
uint8_t uiKeyCodeFirst = KEY_NONE;
uint8_t uiKeyCodeSecond = KEY_NONE;
uint8_t uiKeyCode = KEY_NONE;

int adc_key_in;
int key=-1;
int oldkey=-1;


/*Convert ADC Value to key number

       4 
       | 
    0--1--3
       | 
       2

*/

int get_key(unsigned int input)
{
  if(input<10) return 4;
  else if (input<200) return 0;
  else if (input<400) return 2;
  else if (input<600) return 1;
  else if (input<800) return 3;
  else return -1;

}


void uiStep(void) {
  Serial.println("uiStep");
  adc_key_in = analogRead(0);
  key = get_key(adc_key_in);
  if(key!= oldkey)
  {
    delay(50);
    adc_key_in = analogRead(0);
    key = get_key(adc_key_in);
    if(key!= oldkey)
    {
      oldkey = key;
      if(key >=0){
      uiKeyCodeFirst = KEY_BACK;
      }
      else if (key==0)
       uiKeyCodeFirst = KEY_SELECT;
       else if (key==1)
       uiKeyCodeFirst = KEY_NEXT;
       else if (key==2)
       uiKeyCodeFirst = KEY_PREV;
       else if (key==4)
       uiKeyCodeFirst = KEY_NONE;

       uiKeyCode = uiKeyCodeFirst;
    }
  } 
 delay(100);      
}




#define MENU_ITEMS 4
char *menu_strings[MENU_ITEMS] = { "First Line", "Second Item", "3333333", "abcdefg" };

uint8_t menu_current = 0;
uint8_t menu_redraw_required = 0;
uint8_t last_key_code = KEY_NONE;


void drawMenu(void) {
  uint8_t i, h;
  u8g_uint_t w, d;

  u8g.setFont(u8g_font_6x13);
  u8g.setFontRefHeightText();
  u8g.setFontPosTop();
  
  h = u8g.getFontAscent()-u8g.getFontDescent();
  w = u8g.getWidth();
  for( i = 0; i < MENU_ITEMS; i++ ) {
    d = (w-u8g.getStrWidth(menu_strings[i]))/2;
    u8g.setDefaultForegroundColor();
    if ( i == menu_current ) {
      u8g.drawBox(0, i*h+1, w, h);
      u8g.setDefaultBackgroundColor();
    }
    u8g.drawStr(d, i*h, menu_strings[i]);
  }
}

void updateMenu(void) 
{
  Serial.println("update menu");
  switch (uiKeyCode){
    case KEY_NEXT:
    menu_current++;
    if (menu_current >= MENU_ITEMS) menu_current = 0;
    menu_redraw_required = 1;
    break;
    case KEY_PREV:
    if (menu_current == 0) menu_current - MENU_ITEMS;
    menu_current--;
    menu_redraw_required = 1;
    break;
  }
  uiKeyCode = KEY_NONE;
  
}


void setup() {
  // rotate screen, if required
  // u8g.setRot180();

  Serial.begin(9600);
  uiStep();  // setup key detection and debounce algorithm
  u8g.setContrast(0);
  menu_redraw_required = 1;     // force initial redraw
}

void loop() {  

Serial.println("loop");
  uiStep();  // check for key press
  updateMenu();
    
  if (  menu_redraw_required != 0 ) {
    u8g.firstPage();
    do  {
      drawMenu();
    } while( u8g.nextPage() );
    menu_redraw_required = 0;
  }
 
}