java - Webdriver selenium，java.lang.NullPointerException，尝试查找 Webelement 时

Question

编写了完整的代码来从 Excel 中获取数据并登录 Gmail，但在尝试这样做时，我的浏览器已打开，所需的页面也已打开，并且登录 ID 已从 Excel 中选取并存储在变量 sUsername 中，但无法找到 xpath as- element=driver.findElement(by.id("Email")); 但是当我打印元素时它保存“null”，正如预期的那样是某个地址定位器 ID。此外，通过使用 id 地址，我将与 sendkeys 一起使用，在文本框中输入电子邮件地址。

但显示以下错误:

java.lang.NullPointerException at appModules.SignIN.Execute(SignIN.java:21)

登录类 - 存在定位器问题的位置:at - Login1.userName(driver).sendKeys(sUsername);

public class Login1 {

 //private static WebDriver driver=null;
 private static WebElement element=null;

public static WebElement userName(WebDriver driver) 
{
    try {
        System.out.println("aaa");
    System.out.println("bb");
        element=driver.findElement(By.name("Email"));
        System.out.println("ccc");
    } catch (Exception e) {
        // TODO: handle exception
        System.out.println(element);
    }

return element;
}
public static WebElement btn_login(WebDriver driver)
{
    element= driver.findElement(By.id("next"));
    return element;
}
public static WebElement passWord(WebDriver driver)
{
    element= driver.findElement(By.id("Passwd"));
    return element;
}
public static WebElement btn_SignIN(WebDriver driver)
{
    element= driver.findElement(By.id("signIn"));
    return element;
}
}

这是 SigniN 类，其中 iam 遇到 java 空指针异常 - 存在问题:at- Login1.userName(driver).sendKeys(sUsername);

public class SignIN {
private static WebDriver driver=null;

public static void Execute (int iTestCaseRow) 
{
    String sUsername=ExcelUtils1.getCellData(iTestCaseRow,Constant1.col_UserName);
    System.out.println(sUsername);
 //driver.ma3nage().window().maximize();
     //driver.manage().timeouts().implicitlyWait(10,TimeUnit.SECONDS);

Login1.userName(driver).sendKeys(sUsername);
    //driver.manage().timeouts().implicitlyWait(10,TimeUnit.SECONDS);
    Login1.btn_login(driver).click();
String pass=ExcelUtils1.getCellData(iTestCaseRow, Constant1.col_password1);
Login1.passWord(driver).sendKeys(pass);
Login1.btn_SignIN(driver).click();
}
}

这是我实例化浏览器的地方--

public class Utils1 {
    public static WebDriver driver;

    public static WebDriver OpenBrowser(int iTestCaseRow) {
        String sBrowserName;
        System.out.println(iTestCaseRow);
        sBrowserName = ExcelUtils1.getCellData(iTestCaseRow,
                Constant1.col_browser);
        if (sBrowserName.equals("Mozilla")) {
            driver = new FirefoxDriver();
            // Log.info("New driver instantiated");
            driver.manage().timeouts().implicitlyWait(20, TimeUnit.SECONDS);
            // Log.info("Implicit wait applied on the driver for 10 seconds");
            driver.get(Constant1.URL);
            // Log.info("Web application launched successfully");

        }
        return driver;
    }
}

Answer 1

最好的做法是在内部处理以及显式等待定位元素。如果有页面相关的 Activity ，那么还需要使用等待页面加载。

请按照以下代码操作对于内部等待

protected WebElement waitForPresent(final String locator) {
    // timeout is your default wait timeout in long.
    return waitForPresent(locator, timeout);
}

对于显式等待

protected WebElement waitForPresent(final String locator, long timeout) {
    WebDriverWait wait = new WebDriverWait(driver, timeout);
    WebElement ele = null;
    try {
        ele = wait.until(ExpectedConditions
                .presenceOfElementLocated(locator));
    } catch (Exception e) {
        throw e;
    }
    return ele;
}

protected WebElement waitForNotPresent(final String locator, long timeout) {
    timeout = timeout * 1000;
    long startTime = System.currentTimeMillis();
    WebElement ele = null;
    while ((System.currentTimeMillis() - startTime) < timeout) {
        try {
            ele = findElement(locator);
            Thread.sleep(1000);
        } catch (Exception e) {
            break;
        }
    }
    return ele;
}