예외 : java.lang.NullPointerException

Question

다음 코드를 사용하여 이미지가 웹 페이지에 완전히로드되었는지 확인합니다.

public static boolean IsImageVisible1(WebDriver driver, By locator) 
    { 
    WebElement image = driver.findElement(locator); 
    //if the element not present you'll get the NoSuchElementException exception 
    JavascriptExecutor js = (JavascriptExecutor) driver; 
    boolean imageLoaded1 = (boolean) js.executeScript("return arguments[0].complete && (typeof arguments[0].naturalWidth !== \"undefined\") && (arguments[0].naturalWidth > 0)", image);  
    return imageLoaded1; 
    } 

나는 다음과 같은 예외를 얻고이 방법을 실행하는 동안

java.lang.NullPointerException 
at pack2.image.IsImageVisible1(image.java:58) 
at pack2.image.test(image.java:23) 
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
at java.lang.reflect.Method.invoke(Unknown Source) 
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47) 
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) 
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44) 
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) 
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271) 
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70) 
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50) 
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238) 
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63) 
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236) 
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53) 
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229) 
at org.junit.runners.ParentRunner.run(ParentRunner.java:309) 
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50) 
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) 
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) 
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) 
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) 
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197) 


function call to above method: IsImageVisible1(driver, By.id("homepage-preview")); 

은 제가 자바 스크립트 코드 위의 누락하고 알려 주시기 바랍니다. 사전

Answer 1

1. typeof에서

   덕분에 한 단어이어야한다. 그리고 그것을 고쳐야합니다.

2. 그 후에는 imageLoaded1을 돌려 줄 수 있습니다. if 조건을 넣을 필요가 없습니다.

UPDATE :

executeScript 반환 널 (null) 때문에 아마 NullPointer 예외를 얻고있다.

public static boolean IsImageVisible1(WebDriver driver, By locator) 
    { 
    WebElement image = driver.findElement(locator); 
    //if the element not present you'll get the NoSuchElementException exception 
    JavascriptExecutor js = (JavascriptExecutor) driver; 
    boolean imageLoaded1 = (boolean) js.executeScript("return arguments[0].complete && (typeof arguments[0].naturalWidth !== \"undefined\") && (arguments[0].naturalWidth > 0)", image);  
    return imageLoaded1; 
    }