返回空指针异常 - Java Selenium Webdriver

Question

使用Java在Selenium WebDriver中运行测试时获取Null指针异常。由于某种原因，测试重新调整为null，即使所有内容都被正确声明（我认为？）。

我在这里错过了什么/做错了什么？

//鉴于此代码：

public class HomePage extends DriverSetup{

    @FindBy(className = "ico fa fa-lock")
    static WebElement loginButton;

    public HomePage (WebDriver driver){
        super(driver);
    }


  public static void logInBut(){
        loginButton.click();
  }```



//When running this test:


```public class test1 extends DriverSetup{

    public test1() {
        super(driver);
    }

    @Test
    public void signIn(){

        getDriver().get(URL);

        HomePage.logInBut();

        logInPage.inEmail(" ");
        logInPage.inPassword(" ");


    }```


//Driver Set up:

```public class DriverSetup {

    public static WebDriver driver;

    public DriverSetup(WebDriver driver) {
    }

    public WebDriver getDriver() {
        if(this.driver == null) {
            this.setUp();
        }
        return this.driver;
    }

    public void FindByInitialization (WebDriver driver){
        this.driver = driver;
        PageFactory.initElements(driver, this);
    }

    //Set up Driver
    @BeforeClass //Before executing any test in the class do this
    public static void setUp(){

        System.setProperty("webdriver.chrome.driver", "C:\\Users\\Peter.Redondeiro\\Documents" +
        "\\IDEA projects\\ChromeDriver\\chromedriver_win32\\chromedriver.EXE");

        driver = new ChromeDriver();
        driver.manage().window().maximize(); //maximise window when open
    }

    //clear all the cookies after executing each test
    @After
    public void clearCookies(){
        driver.manage().deleteAllCookies(); //delete all the cookies
    }

    //Close browser after executing all the tests in the class
    @AfterClass
    public static void closeBrowser(){
        driver.close();
    }

}```


//Log in page object:

public class logInPage extends DriverSetup{

    //Find the input email box in Login page
    @FindBy(id = "inputEmail")
    private static WebElement inputEmail;

    //Find input password box in Login page
    @FindBy(id = "inputPassword")
    private static WebElement inputPassword;

    //Find LogIn button in Login page
    @FindBy(id = "login")
    private static WebElement logInButton;

    public logInPage(WebDriver driver) {
        super(driver);
    }

    //Confirm that you are on the Login page
    public static String confirmationHeader(){
        return header.getText();
    }

    //Method to enter email in email box
    public static void inEmail(String inEmail){
       inputEmail.sendKeys(inEmail + emailGenerator.randomEmailGenerator());
    }

    //Method to enter password in password box
    public static void inPassword(String PassInput){
       inputPassword.sendKeys(PassInput + passwordGenerator.randomPasswordGenerator());
    }
}```

这是上面代码执行的堆栈跟踪：

java.lang.NullPointerException
    at logInPage.inEmail(logInPage.java:46)
    at test1.signIn(test1.java:15)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)


Process finished with exit code -1

Answer 1

你正在线上获得NPE（空指针异常）

loginButton.click();

它意味着你正在对一个获得null值的对象进行一些操作，在这种情况下它只是你的loginButton

现在问题出现了，为什么登录按钮在初始化时为空

@FindBy(className = "ico fa fa-lock")
static WebElement loginButton;

这是可能的，因为Web驱动程序无法找到此元素，因此它为null

尝试以下建议

public HomePage(WebDriver driver) {
    super(driver);
    PageFactory.initElements(driver, this);
}

如果这不起作用尝试像这样的单个类名称

@FindBy(className = "ico")
private WebElement loginButton;

@FindBy(className = "login")
List<WebElement> buttons;

而点击这样

buttons.get(0).click();

其他尝试使用javascript点击直接，它肯定会工作

((JavascriptExecutor)driver).executeScript("document.getElementsByClassName('login')[0].click()");

Answer 2

请查看HomePage.java中的第55行

它说

loginButton.click();

Nullpointer是因为loginButton为null，可能是因为它未初始化。

很可能是因为它无法通过您提到的类找到元素。

你可能想用'。'在班级名称前面

Answer 3

loginButton是null，因为你指定的定位器与任何东西都不匹配。 className将一个类作为参数，你使用三个。要使用多个课程，您需要使用cssSelector

@FindBy(css = ".ico.fa.fa-lock")
static WebElement loginButton;

或者xpath

@FindBy(xpath = "//*[@class='ico fa fa-lock']")
static WebElement loginButton;

别忘了把它初始化PageFactory.initElements(driver, HomePage)

Answer 4

请尝试以下代码。

@FindBy(className = "login")
static WebElement loginButton;

要么

@FindBy(xpath ="//a[@class='login']")
static WebElement loginButton;

Answer 5

致@Ravi，我的查询的答案如下：

public class HomePage extends DriverSetup{

    @FindBy(className = "login")
    private static List<WebElement> buttons;

    public HomePage (WebDriver driver){
        super(driver);
    }

  public static void logInBut(){
      ((JavascriptExecutor)driver).executeScript("document.getElementsByClassName('login')[0].click()");
  }
}
//Trying with javascript click because of environment issue driver was not able to find elements with @FindBy, hence the web element was null and it was throwing NullPointerException

//If you need to read through to understand please see the comments and read @Ravi's comments in particular!