org.openqa.selenium.ElementNotVisibleException: element not visible

Question

My test fall down when I run test, I run the test again, test is pass, code do not change but the result is different. Why? This is my code:

    public ProductPage clickOnAccessories(){

        //Click on link “Accessories”
        waitForElementToBeDisplayed(driver.findElement(By.xpath("//a[text()='Product Category']")), 200);
        Actions act = new Actions(driver);
        act.moveToElement(driver.findElement(By.xpath("//a[text()='Product Category']")));
        act.perform();

        link_Accessories.click();

        //Expected: Page “Accessories” has been opened with correct url, headline, tab title
        Assert.assertTrue(driver.getCurrentUrl().equals("http://store.demoqa.com/products-page/product-category/accessories/"));
        Assert.assertTrue(driver.getTitle().contains("Accessories"));
        Assert.assertTrue(tab_title_Accessories.getText().contains("customers"));

        return PageFactory.initElements(getDriver(), ProductPage.class);
    }


public void waitForElementToBeDisplayed(final WebElement element, int defaultWaitTime) {
    for (int i = 500; i < defaultWaitTime; i += 100) {
        Utils.waitTime(500);
        if (isElementDisplayed(element)) { return; }
    }
}

protected boolean isElementDisplayed(final WebElement element) {
    boolean isDisplayed = false;
    try {
        final String tagName = element.getTagName();
        if (!tagName.isEmpty()) { isDisplayed = element.isDisplayed(); }
        return isDisplayed;
    } catch (final Exception e) { }
    return isDisplayed;
} 

This is my error:

org.openqa.selenium.ElementNotVisibleException: element not visible
  (Session info: chrome=55.0.2883.87)
  (Driver info: chromedriver=2.25.426923 (0390b88869384d6eb0d5d09729679f934aab9eed),platform=Windows NT 6.3.9600 x86_64) (WARNING: The server did not provide any stacktrace information)
Command duration or timeout: 51 milliseconds
Build info: version: 'unknown', revision: 'c7b525d', time: '2016-09-01 14:57:44 -0700'
System info: host: 'Gaga', ip: '192.168.1.6', os.name: 'Windows 8.1', os.arch: 'amd64', os.version: '6.3', java.version: '1.8.0_101'
Driver info: org.openqa.selenium.chrome.ChromeDriver
Capabilities [{applicationCacheEnabled=false, rotatable=false, mobileEmulationEnabled=false, networkConnectionEnabled=false, chrome={chromedriverVersion=2.25.426923 (0390b88869384d6eb0d5d09729679f934aab9eed), userDataDir=C:\Users\Dragana\AppData\Local\Temp\scoped_dir10100_17794}, takesHeapSnapshot=true, pageLoadStrategy=normal, databaseEnabled=false, handlesAlerts=true, hasTouchScreen=false, version=55.0.2883.87, platform=WIN8_1, browserConnectionEnabled=false, nativeEvents=true, acceptSslCerts=true, locationContextEnabled=true, webStorageEnabled=true, browserName=chrome, takesScreenshot=true, javascriptEnabled=true, cssSelectorsEnabled=true}]
Session ID: a24c7146c1accfdd3ef521786f4cb399

Answer 1

You must try Webdriver wait to eliminate this error. Enter you xpath expression where you want to trigger wait.

WebDriverWait wait = new WebDriverWait(driver, 30);
    wait.until(ExpectedConditions.elementToBeClickable(By.xpath("<Enter your xpath expression here>")));

Answer 2

You might need to use embedded methods to wait until target element becomes visible:

// Set your own value of timeoutInSeconds
WebDriverWait wait = new WebDriverWait(webDriver, timeoutInSeconds);
wait.until(ExpectedConditions.visibilityOfElementLocated(By.xpath("//a[text()='Product Category']")));