当我试图在POM selenium webdriver中使用TestNG将login转换为单独的方法时，java出现空指针异常

Question

我一直在尝试使用TestNG在SeleniumWebDriver上构建POM框架。为页面元素和页面操作（单击、发送键等）创建单独的类。到目前为止，它运行良好。然后我决定使用commonFunctions类进行登录。在该实现之后，它将不工作，并抛出空指针异常。我不太擅长OOPS概念。问题是我什么时候打电话

commonFunction.login(username, password);

有人能帮我找出问题的原因吗

逻辑测试类

package Tests;
import org.openqa.selenium.*;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.testng.Assert;
import org.testng.annotations.*;
import lib.excelDataConfig;
import lib.pageActions;
import pages.HomepageObjects;
import pages.LoginObjects;
import functions.commonFunctions;

public class LoginTest{
    public String baseUrl = "https://sampleurl.com/";
    String driverPath = "C:\\selenium\\geckodriver-v0.27.0-win64\\geckodriver.exe";
    public WebDriver driver ;
    public pageActions actionObj;
    public LoginObjects loginObj; 
    public HomepageObjects homepageObj; 
    public commonFunctions commonFunction;
    
    excelDataConfig excel = new excelDataConfig("C:\\Users\\vsaisiva\\eclipse-workspace\\TestNgProject\\datasource\\UserData.xlsx");
   @BeforeTest
   public void LaunchTest() {
        System.out.println("launching firefox browser"); 
        System.setProperty("webdriver.gecko.driver", driverPath);
        driver = new FirefoxDriver();
        loginObj = new LoginObjects(driver);
        homepageObj = new HomepageObjects(driver);
        actionObj = new pageActions(driver);
        commonFunction = new commonFunctions(driver);
        driver.get(baseUrl);
  }    
  @Test (priority=1)
  public void verifyHomepageTitle() {
      String expectedTitle = "RM Assessment Hub";
      String actualTitle = driver.getTitle();
      Assert.assertEquals(actualTitle, expectedTitle);
  }
  @Test (priority=2)
  public void LoginAndVerify() {
      //driver.findElement(By.id("usernameBox")).sendKeys("bobsmith@email.com");
      String username = "user@email.com";
      String password = "user";
      commonFunction.login(username, password);
      actionObj.waitForVisibility(homepageObj.loginConfirmText);
      if(actionObj.isElementPresent(homepageObj.loginConfirmText)) {
          System.out.println("Login success for user:"+username); 
          homepageObj.clickUsermenu();
          homepageObj.clickLogout();
      }
    } 
      
  @AfterTest
  public void CloseTest() {
      driver.close();
}    
}

登录对象类：

package pages;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.By;

public class LoginObjects {
    WebDriver driver = null;
    public By usernameBox = By.id("usernameBox");
    public By passwordBox = By.id("passwordBox");
    public By loginbutton = By.id("loginbutton");
    public LoginObjects(WebDriver driver) {
        this.driver=driver;
    }
}

页面操作类

package lib;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.support.ui.ExpectedConditions;
import org.openqa.selenium.support.ui.WebDriverWait;
import org.openqa.selenium.By;


public class pageActions {
    WebDriver driver = null;
    public pageActions(WebDriver driver){
        this.driver = driver;
    }
    public void click(By locator){
        driver.findElement(locator).click();
    }
    public void type(By locator, String text){
        driver.findElement(locator).clear();
        driver.findElement(locator).sendKeys(text);
    }
    public void waitForVisibility(By locator) throws Error{
        WebDriverWait wait = new WebDriverWait(driver, 15);
          wait.until(ExpectedConditions.visibilityOfElementLocated(locator));
    }
    public boolean isElementPresent(By locator) throws Error{
        return driver.findElement(locator).isDisplayed();
    }
}

通用函数类：

package functions;

import org.openqa.selenium.WebDriver;
import pages.LoginObjects;
import lib.pageActions;


public class commonFunctions {
    WebDriver driver = null;
    public commonFunctions(WebDriver driver) {
        this.driver=driver;
    }
    public pageActions actionObj = new pageActions(driver);
    public LoginObjects loginObj = new LoginObjects(driver); 
    public void login(String username, String password){
        actionObj.type(loginObj.usernameBox, username);
        actionObj.type(loginObj.passwordBox, password);
        actionObj.click(loginObj.loginbutton);
    }
}