SSD1306 OLED dipslay on olimexino STM32

it is working but display is doing little flash when changing values
i used this example

function showData() {
 lcd.clear();
 lcd.setCursor(0,0);
 lcd.print("Current data:");
 lcd.setCursor(4,1);
 lcd.print("D1 = "+analogRead(D1));
}
setInterval(showData, 1000);

I think it should only flash in section where the D1 value is, not all display?