This sample code is for measuring surrounding air pressure's tutorial using Grove Air Pressure Sensor(BMP280)

Barometer_grove.ino

#include "Seeed_BMP280.h"
#include <Wire.h>
#include <Arduino.h>
#include <U8x8lib.h>

U8X8_SSD1306_128X64_ALT0_HW_I2C u8x8(/* reset=*/ U8X8_PIN_NONE);
BMP280 bmp280;

void setup() {
  Serial.begin(9600);
  u8x8.setBusClock(100000);  // If you breakout other modules, please enable this line
  u8x8.begin();
  u8x8.setPowerSave(0);
  u8x8.setFlipMode(1);
  if (!bmp280.init()) {
    Serial.println("Device not connected or broken!");
  }
}
void loop() {
  float pressure;
  u8x8.setFont(u8x8_font_chroma48medium8_r);
  u8x8.setCursor(0, 0);
  u8x8.print("P:");
  u8x8.print(pressure = bmp280.getPressure());
  u8x8.print("Pa"); 
  u8x8.setCursor(0, 30);
  u8x8.print("A:");
  u8x8.print(bmp280.calcAltitude(pressure));
  u8x8.print("m");
  u8x8.refreshDisplay();
  delay(200);

    //float pressure;
    //get and print temperatures
    Serial.print("Temp: ");
    Serial.print(bmp280.getTemperature());
    Serial.println("C"); // The unit for Celsius because original arduino don't support speical symbols
    //get and print atmospheric pressure data
    Serial.print("Pressure: ");
    Serial.print(pressure = bmp280.getPressure());
    Serial.println("Pa");
    //get and print altitude data
    Serial.print("Altitude: ");
    Serial.print(bmp280.calcAltitude(pressure));
    Serial.println("m");
    Serial.println("\n");//add a line between output of different times.
    delay(1000);

}