我也有这个问题。这是由于驱动程序在遇到警报时的默认行为。默认行为设置为“接受”，因此警报自动关闭，并且 switchTo().alert() 找不到它。

解决方案是修改驱动程序的默认行为（“IGNORE”），使其不关闭警报：

DesiredCapabilities dc = new DesiredCapabilities();
dc.setCapability(CapabilityType.UNEXPECTED_ALERT_BEHAVIOUR, UnexpectedAlertBehaviour.IGNORE);
d = new FirefoxDriver(dc);

然后你可以处理它：

try {
    click(myButton);
} catch (UnhandledAlertException f) {
    try {
        Alert alert = driver.switchTo().alert();
        String alertText = alert.getText();
        System.out.println("Alert data: " + alertText);
        alert.accept();
    } catch (NoAlertPresentException e) {
        e.printStackTrace();
    }
}

您可以使用WaitSelenium WebDriver 中的功能来等待警报，并在警报可用时接受它。

在 C# 中 -

public static void HandleAlert(IWebDriver driver, WebDriverWait wait)
{
    if (wait == null)
    {
        wait = new WebDriverWait(driver, TimeSpan.FromSeconds(5));
    }

    try
    {
        IAlert alert = wait.Until(drv => {
            try
            {
                return drv.SwitchTo().Alert();
            }
            catch (NoAlertPresentException)
            {
                return null;
            }
        });
        alert.Accept();
    }
    catch (WebDriverTimeoutException) { /* Ignore */ }
}

它在 Java 中的等价物 -

public static void HandleAlert(WebDriver driver, WebDriverWait wait) {
    if (wait == null) {
        wait = new WebDriverWait(driver, 5);
    }

    try {
        Alert alert = wait.Until(new ExpectedCondition<Alert>{
            return new ExpectedCondition<Alert>() {
              @Override
              public Alert apply(WebDriver driver) {
                try {
                  return driver.switchTo().alert();
                } catch (NoAlertPresentException e) {
                  return null;
                }
              }
            }
        });
        alert.Accept();
    } catch (WebDriverTimeoutException) { /* Ignore */ }
}

它将等待 5 秒钟，直到出现警报，如果预期的警报不可用，您可以捕获异常并处理它。

您是否在 try/catch 块中切换到警报？您可能还想添加等待超时以查看警报是否在特定延迟后出现

try {
    // Add a wait timeout before this statement to make 
    // sure you are not checking for the alert too soon.
    Alert alt = driver.switchTo().alert();
    alt.accept();
} catch(NoAlertPresentException noe) {
    // No alert found on page, proceed with test.
}

UnhandledAlertException 

当它遇到一个未处理的警告框弹出时抛出。除非发现警报框场景，否则您需要将代码设置为正常运行。这克服了你的问题。

       try {
            System.out.println("Opening page: {}");
            driver.get({Add URL});
            System.out.println("Wait a bit for the page to render");
            TimeUnit.SECONDS.sleep(5);
            System.out.println("Taking Screenshot");
            File outputFile = ((TakesScreenshot) driver).getScreenshotAs(OutputType.FILE);
            String imageDetails = "C:\\images";
            File screenShot = new File(imageDetails).getAbsoluteFile();
            FileUtils.copyFile(outputFile, screenShot);
            System.out.println("Screenshot saved: {}" + imageDetails);
        } catch (UnhandledAlertException ex) {
            try {
                Alert alert = driver.switchTo().alert();
                String alertText = alert.getText();
                System.out.println("ERROR: (ALERT BOX DETECTED) - ALERT MSG : " + alertText);
                alert.accept();
                File outputFile = ((TakesScreenshot) driver).getScreenshotAs(OutputType.FILE);
                String imageDetails = "C:\\Users";
                File screenShot = new File(imageDetails).getAbsoluteFile();
                FileUtils.copyFile(outputFile, screenShot);
                System.out.println("Screenshot saved: {}" + imageDetails);
                driver.close();
            } catch (NoAlertPresentException e) {
                e.printStackTrace();
            }
        } 

单击事件后添加下面的代码来处理

    try{
         driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
       }
 catch (org.openqa.selenium.UnhandledAlertException e) {                
         Alert alert = driver.switchTo().alert(); 
         String alertText = alert.getText().trim();
         System.out.println("Alert data: "+ alertText);
         alert.dismiss();}

...做其他事情 driver.close();