/*
   https://forum.arduino.cc/t/multiple-pages-on-i2c-lcd-display/1095011


 */

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 20, 4);

const uint8_t maxScreens = 3;
uint8_t currentScreen = 0;
const uint8_t btnPin = 7;


void nextScreen() {
  currentScreen++;
  if (currentScreen >= maxScreens) currentScreen = 0;
  switch (currentScreen) {
    case 0 : screenA(); break;
    case 1 : screenB(); break;
    case 2 : screenC(); break;
  }
}


void screenA() {
  lcd.clear();
  lcd.print(F("A something here"));
}

void screenB() {
  lcd.clear();
  lcd.print(F("B different screen"));
}

void screenC() {
  lcd.clear();
  lcd.print(F("C another screen"));
}

void setup() {
  pinMode(btnPin, INPUT_PULLUP);
  lcd.init();
  lcd.backlight();
  lcd.print("start");
}

void loop() {
  if (digitalRead (btnPin) == LOW)  {
    nextScreen();
    delay(500); // dirty delay - use a real state change detection instead;
  }
}