如何获得WebDriver为我的听众级时使用"公线程本地<WebDriver>webdriver=new线程本地<WebDriver>();"的方法

我不断收到异常为我的听众的WebDriver. 这是因为我用线程本地上我的WebDriver在基类? 如果是这样我怎么试验的情况下的驱动我的听众的onTestSuccess方法？

这是我的听众类：

@Override
    public void onTestSuccess(ITestResult result) {
        extentTest.get().log(Status.PASS,"Test Passed");
        WebDriver driver = null;
        Object testObject = result.getInstance();
        Class clazz = result.getTestClass().getRealClass();
        try {
            driver = (WebDriver)clazz.getField("webdriver").get(testObject);
        } catch (Exception e) {
        }
        try {
            extentTest.get().addScreenCaptureFromPath(getScreenShotPath(result.getMethod().getMethodName(), driver), result.getMethod().getMethodName());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

BaseClass:

public ThreadLocal<WebDriver> webdriver = new ThreadLocal<WebDriver>();


@BeforeClass
public void setup() {
    Reporter.log("@@@@@ Setup @@@@@",true);
    ExtentReports extent = ExtentReport.extentReportGenerator();
}


@BeforeMethod
public void startBrowser() {
    WebDriverFactory webDriverFactory = new WebDriverFactory();
    webDriverFactory.setDriver();
    webdriver.set(webDriverFactory.getDriver());
    webdriver.get().get(baseURL);

测试用例级：

@Test(dataProvider = "jsonData", dataProviderClass = TestData.class)
public void  testAggregator(String jSon) throws ParseException {
    extent.createTest("Test The Welcome Page");
    welcomePageImpl = new WelcomePageImpl(webdriver.get());
    welcomePageImpl.getAggregatorRequest(webdriver.get(),jSon);
}

例外：

java.lang.NullPointerException
    at main.java.com.shoppingCart.testCases.BaseClass.getScreenShotPath(BaseClass.java:71)
    at main.java.com.shoppingCart.utilities.Listeners.onTestSuccess(Listeners.java:37)
    at org.testng.internal.TestListenerHelper.runTestListeners(TestListenerHelper.java:70)
    at org.testng.internal.TestInvoker.runTestResultListener(TestInvoker.java:219)
    at org.testng.internal.TestInvoker.invokeMethod(TestInvoker.java:651)
    at org.testng.internal.TestInvoker.invokeTestMethod(TestInvoker.java:173)
    at org.testng.internal.MethodRunner.runInSequence(MethodRunner.java:46)
    at org.testng.internal.TestInvoker$MethodInvocationAgent.invoke(TestInvoker.java:816)
    at org.testng.internal.TestInvoker.invokeTestMethods(TestInvoker.java:146)
    at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:146)
    at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:128)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)