Selenium 2: something wrong with code “driver.findElement(By.name("username")).sendKeys("");”

I use the code

driver.findElement(By.name("username")).sendKeys("name");
drive开发者_如何转开发r.findElement(By.name("password")).sendKeys("12345");

to login to a website. Sometimes it will work, sometimes it won't, the error given is

Exception in thread "main" org.openqa.selenium.NoSuchElementException: Unable to locate element: {"method":"name","selector":"username"}

The problem is that sometimes it will work. Should I perhaps use Byxpath（）?

You can use WebDriverWait with conditions to wait for Elements:

public class MyTestClass{

    private static final int MAX_WAIT_TIME_SEC = 60;
    private WebDriverWait wait;
    [...]

    public void setField(String fieldname, String text){
        wait = new WebDriverWait(driver, MAX_WAIT_TIME_SEC);
        wait.until(new NameExpectedCondition(xpath));
        WebElement element = driver.findElement(By.name(fieldname));
        if(element != null){
            element.sendKeys(text);
        }
        [...]
    }

    public void foo()
}

With NameExpectedCondition:

import org.openqa.selenium.By;

public class NameExpectedCondition implements ExpectedCondition<Boolean> {

private String fieldName;

public NameExpectedCondition(String fieldName)
{
    this.fieldName= fieldName;
}

public Boolean apply(WebDriver d) {
    d.findElement(By.Name(fieldName));
    return Boolean.TRUE;
}

}

Please make also sure you're searching for the element in the correct frame.

You might not be waiting till the element loads in the page. Its a good practice to use selenium.isElementPresent(locator) or selenium.isVisible(locator) before the sendKeys or similar commands command execution.

There is the most simple way to solve this problem:

driver.Manage().Timeouts().ImplicitlyWait(new TimeSpan(0, 0, 10));

It will handle all NoSuchElementExceptions just trying to refind an element.

Please add this command before you send FindElement:

String strTemp = driver.PageSource;

You'll see the source doesn't load the whole page.