Question

Selenium WebDriver Java

任何人都知道如何执行此脚本js.executeScript("window.addEventListener('load',function(){document.getElementsByTagName('script')[1].src='google.com'})");

或

js.executeScript("window.load = function()
{document.getElementsByTagName('script')[1].src='google.com'})");

此脚本返回null。 Eclipse说：线程中的异常＆＃34; main＆＃34;显示java.lang.NullPointerException 在autotesting.itacademy.main（itacademy.java:58）

这里的主要代码是：

package autotesting;

import org.openqa.selenium.JavascriptExecutor;
import org.openqa.selenium.WebDriver;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.concurrent.TimeUnit;

import org.apache.commons.io.FileUtils;
import org.openqa.selenium.*;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.openqa.selenium.logging.LogEntries;
import org.openqa.selenium.support.ui.Select;
import org.openqa.selenium.By;
import org.openqa.selenium.JavascriptExecutor;
import org.openqa.selenium.OutputType;
import org.openqa.selenium.TakesScreenshot;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;

//for read and write from file
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.Scanner;

public class itacademy {

     private static WebDriver driver = null;

     public static JavascriptExecutor js = (JavascriptExecutor) driver;

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub

        JavascriptExecutor js = (JavascriptExecutor) driver;

        driver = new FirefoxDriver();
        driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
        driver.manage().window().maximize();        
        driver.get("http://office.co.uk/");

        js.executeScript("window.addEventListener('load',function(){document.getElementsByTagName('script')[1].src='google.com'})");
            }}

提前致谢

Answer 1

您永远不会初始化JavascriptExecutor。在这里查看，您将driver指定为null，然后尝试将其强制转换为JavascriptExecutor并且从不对其进行初始化：

private static WebDriver driver = null; // driver is null
public static JavascriptExecutor js = (JavascriptExecutor) driver; // js is null

稍后，您将js分配给driver，然后初始化您的驱动程序对象，此处：

JavascriptExecutor js = (JavascriptExecutor) driver; // js is null
driver = new FirefoxDriver(); // driver is now an object

但是当你用js做任何事情时，它仍然是空的：

js.executeScript("window.addEventListener('load',function({document.getElementsByTagName('script')[1].src='google.com'})"); // It's still null here!

您需要正确初始化js对象。顺便说一句，你已经宣布js为班级成员，为什么要立即在主要成员中重新分配？

public static JavascriptExecutor js = (JavascriptExecutor) driver;
JavascriptExecutor js = (JavascriptExecutor) driver; //  This line is unnecessary in main

如何在selenium中执行js？

1 个答案: