NullPointerException：

问：

我想尝试在我的代码中实现页面对象模型。第一页将负责打开网址，并提供用户名和密码。 目前，我的代码在不找到元素的情况下打开 url 并加载网页，然后打开一个新的空白窗口并重复三到四次。 尝试定位元素时崩溃。谁能告诉我我哪里犯了错误。我已将以下详细信息存储在 Config 中。我一遍又一遍地检查代码，但找不到问题

public class Base {
               public static WebDriver driver;
               public static Properties prop;
            public Base(){
                    try {
                        prop = new Properties();
                        FileInputStream ip = new FileInputStream("C:\\config\\config.properties");
                        prop.load(ip);
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
            
                }
            
                public static void initilization()
                {
                 String browsername = prop.getProperty("browser");
                 if (browsername.equals("chrome")){
                     
                     System.setProperty("webdriver.chrome.driver","C:\\Users\\chromedriver.exe");
                     driver= new ChromeDriver();
                }
                  driver.manage().window().maximize();
                  driver.get(prop.getProperty("url"));
                  driver.manage().timeouts().pageLoadTimeout(Duration.ofSeconds(70));
                  driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(70));
                 
                }
            
            }

登录页面 ：

      public class LoginPage extends Base {
        @FindBy(name = "username")
        WebElement username;
    
        @FindBy(name = "password")
        WebElement password;
    
        @FindBy(xpath = "//input[@type='submit']")
        WebElement loginbutton;
    
        @FindBy(xpath = "//button[contains(text(),'Sign Up')]")
        WebElement SignUpButton;
    
        @FindBy(xpath= "//img[contains(@class='img-responsive')]")
        WebElement crmlogo;
    
        public void LoginPage()
    {
        PageFactory.initElements(driver,this);
    }
    
    public boolean logo()
    {
        return crmlogo.isDisplayed();
    }
    
    public String validatetitleofpage()
    {
        return driver.getTitle();
    
    }
    public HomePage login(String un,String psd)
    {
        username.sendKeys(un);
        password.sendKeys(psd);
        loginbutton.click();
        return new HomePage();
    }
    
    }

这是我调用所有方法的 LoginTest：

        public class LoginPageTest extends Base {
        LoginPage LoginPage;
        HomePage HomePage;
        
            public LoginPageTest()
            { super();
            }
         @BeforeMethod
            public void setup()
            {
                initilization();
                LoginPage = new LoginPage();
            }
        
            @Test (priority = 1)
            public void loginPageTitleTest()
            {
                String title = LoginPage.validatetitleofpage();
                Assert.assertEquals(title,"title details");
            }
        
            @Test (priority = 2)
            public void logoTest()
            {
                boolean logotrue=LoginPage.logo();
                Assert.assertTrue(logotrue);
            }
        
            @Test(priority = 3)
            public void logintest()
            {
                HomePage= LoginPage.login(prop.getProperty("unme"),prop.getProperty("pwd"));
            }
        
            @AfterMethod
            public void teardown()
            {
                driver.quit();
        
            }
        }
        
     
    
    

下面是错误的

 java.lang.NullPointerException
   at com.crm.qa.pages.LoginPage.logo(LoginPage.java:31 undefined)
   at com.crm.qa.Testcases.LoginPageTest.logoTe0st(LoginPageTest.java:37 undefined)
   at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at 
                java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
   at `enter code 
          here`java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.base/java.lang.reflect.Method.invoke(Method.java:566 undefined)
                at`org.testng.internal.MethodInvocationHelper.invokeMethod`(MethodInvocationHelper.java:133)
   at `org.testng.internal.TestInvoker.invokeMethod`(TestInvoker.java:598 undefined)
   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:824)
   at org.testng.internal.TestInvoker.invokeTestMethods(TestInvoker.java:146 undefined)
            

配置文件

    url = https://classic.crmpro.com/
    unme = abcd
    pwd =  Abcd
    browser = chrome**