Question

我第一次使用EventListener但面临异常。请任何人都可以帮助。

线程中的异常＆＃34; main＆＃34;显示java.lang.NullPointerException 在seleniumTest.EventListener.beforeFindBy（EventListener.java:62）

package seleniumTest;

import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.openqa.selenium.support.events.EventFiringWebDriver;


public class MainClass {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        WebElement element ;
        WebDriver driver = new FirefoxDriver();
        EventFiringWebDriver eventDriver = new EventFiringWebDriver(driver);
        EventListener listener = new EventListener();

        eventDriver.register(listener);
        eventDriver.manage().window().maximize();
        eventDriver.get("https://www.google.co.in");
//      element = eventDriver.findElement(By.id("sb_ifc0"));
//      element.sendKeys("Shantaveer");
        element = eventDriver.findElement(By.xpath("//input[@type= 'submit']"));
        element.click();

    }

}

    package seleniumTest;

import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.support.events.WebDriverEventListener;

public class EventListener implements WebDriverEventListener{

    public void afterChangeValueOf(WebElement arg0, WebDriver arg1) {
        // TODO Auto-generated method stub

        System.out.println("inside method afterChangeValueOf on " + arg0.toString());
    }

    public void afterClickOn(WebElement arg0, WebDriver arg1) {
        // TODO Auto-generated method stub
        System.out.println("inside method afterClickOn on " + arg0.toString());
    }

    public void afterFindBy(By arg0, WebElement arg1, WebDriver arg2) {
        // TODO Auto-generated method stub
        System.out.println("Find happened on " + arg1.toString() 
                + " Using method " + arg0.toString());
    }

    public void afterNavigateBack(WebDriver arg0) {
        // TODO Auto-generated method stub

        System.out.println("Inside the after navigateback to " + arg0.getCurrentUrl());
    }

    public void afterNavigateForward(WebDriver arg0) {
        // TODO Auto-generated method stub
        System.out.println("Inside the afterNavigateForward to " + arg0.getCurrentUrl());
    }

    public void afterNavigateTo(String arg0, WebDriver arg1) {
        // TODO Auto-generated method stub
        System.out.println("Inside the afterNavigateTo to " + arg0);
    }

    public void afterScript(String arg0, WebDriver arg1) {
        // TODO Auto-generated method stub
        System.out.println("Inside the afterScript to, Script is " + arg0);
    }

    public void beforeChangeValueOf(WebElement arg0, WebDriver arg1) {
        // TODO Auto-generated method stub

        System.out.println("Inside the beforeChangeValueOf method");
    }

    public void beforeClickOn(WebElement arg0, WebDriver arg1) {
        // TODO Auto-generated method stub
        System.out.println("About to click on the " + arg0.toString());

    }

    public void beforeFindBy(By arg0, WebElement arg1, WebDriver arg2) {
        // TODO Auto-generated method stub
        System.out.println("Just before finding element " + arg1.toString());

    }

    public void beforeNavigateBack(WebDriver arg0) {
        // TODO Auto-generated method stub
        System.out.println("Just before beforeNavigateBack " + arg0.getCurrentUrl());

    }

    public void beforeNavigateForward(WebDriver arg0) {
        // TODO Auto-generated method stub
        System.out.println("Just before beforeNavigateForward " + arg0.getCurrentUrl());

    }

    public void beforeNavigateTo(String arg0, WebDriver arg1) {
        // TODO Auto-generated method stub
        System.out.println("Just before beforeNavigateTo " + arg0);
    }

    public void beforeScript(String arg0, WebDriver arg1) {
        // TODO Auto-generated method stub
        System.out.println("Just before beforeScript " + arg0);
    }

    public void onException(Throwable arg0, WebDriver arg1) {
        // TODO Auto-generated method stub
        System.out.println("Exception occured at " + arg0.getMessage());

    }


    @Override
    public void afterNavigateRefresh(WebDriver arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void beforeNavigateRefresh(WebDriver arg0) {
        // TODO Auto-generated method stub

    }

}

Answer 1

检查类似的issue 1589：

在beforeFindBy界面上实施afterFindBy和WebDriverEventListener方法时，我们会获得NullPointerException。
webElement未传递给侦听器。按对象正确传递。

documentation确实提到了：

void beforeFindBy(By by,
                  WebElement element,
                  WebDriver driver)

在WebDriver.findElement(...)，WebDriver.findElements(...)，WebElement.findElement(...)或WebElement.findElements(...)之前调用。

参数：
     如果调用element的查找方法，
WebDriver - 将为null。

author lukeis评论in the issue：

WebElement参数的意图是显示用作findBy的引用的元素，而不是找到的元素。
当我们使用除WebElement之外的findElement时，
WebDriver不为空，例如使用findElement的{{1}}方法。

所以你应该保护Webelement arg1：它可以是null，如记录所示。

使用EventListener时遇到错误

1 个答案: