title: Null Pointer Exception Android Driver
body: <p>I have ajava/serenity/appium project and currently my capabilites are set in a serenity properties file. Below I want to perform a scroll but I receive a null pointer exception error for my androidDriver. I am unsure on how to fix the null pointer exception.</p>
  
  <pre><code>public class ScrollingMethods extends PageObject {
  
          AndroidDriver androidDriver;
  
  
      public void scrollDown() {
  
          int pressX = androidDriver.manage().window().getSize().width / 2;
  
          int bottomY = androidDriver.manage().window().getSize().height * 4/5;
  
          int topY = androidDriver.manage().window().getSize().height / 8;
  
          scroll(pressX, bottomY, pressX, topY);
      }
  
  
      public void scroll(int fromX, int fromY, int toX, int toY) {
          TouchAction touchAction = new TouchAction(androidDriver);
          touchAction.longPress(fromX, fromY).moveTo(toX, toY).release().perform();
      }
  }
  </code></pre>