Selenium WebDriver:使用WebDriver.findElement定位时，等待元素出现 [英] Selenium WebDriver: wait for element to be present when locating with WebDriver.findElement is impossible

问题描述

等待 WebElement 与 WebDriverWait 和 ExpectedConditions 一起显示很方便.

It's convenient to wait for an WebElement to be present with WebDriverWait and ExpectedConditions.

问题是，如果 WebElement.findElment 是定位元素的唯一可能方法，因为它没有ID，没有名称，没有唯一的类?

The problem is, what if WebElement.findElment was the only possible way to locate the element , 'cause it has no id, no name, no unique class?

WebDriverWait 的构造函数仅接受 WebDriver 作为参数，而不接受 WebElement .

WebDriverWait's constructor accepts only WebDriver as arguments, not WebElement.

我已经设置了 implicitlyWait 时间，因此使用 try {} catch(NoSuchElementException e){} 似乎不是一个好主意，因为我不知道"不想等那么长时间.

I've set the implicitlyWait time, so it seems not a good idea to use try{} catch(NoSuchElementException e){}, 'cause I don't want to wait that long time for this element.

这是场景:

有一个网页，其中的表单包含许多 input 标签.每个 input 标签都有格式要求.

There's one web page with a form containing many input tags. Each input tag has a format requirement.

当不满足格式要求时，在此 input 标记之后将出现动态的 div 标记.

A dynamic div tag would be present after this input tag when the format requirement is not satisfied.

由于有很多 input 标签，我创建了一个通用方法，如:

As there're so many input tags, I create a general method like:

public WebElement txtBox(String name) {
    return driver.findElement(By.name(name));
}

而不是为每个 input 标签创建数据成员.

instead of creating a data member for each input tag.

然后我创建一个方法 isValid 来检查某些 input 中的用户输入是否有效.我在 isValid 中要做的就是检查在 inputboxToCheck 之后是否存在一个 div 标记，其代码如下:

Then I create a method isValid to check whether user inputs in some input are valid. All I should do in isValid is to check whether a div tag is present after inputboxToCheck, with code like this:

public boolean isValid(WebElement inputboxToCheck) {
    WebElementWait wait = new WebElementWait(inputboxToCheck, 1);
    try {
        wait.until(ExpectedConditions.presenceOfElementLocated(By.xpath("./following-sibling::div")));
        return false;
    } catch (TimeOutException e) {
        return true;
    }    
}

WebElementWait 是一个虚构的类(不存在)，其作用与 WebDriverWait 相同.

WebElementWait is an imaginary (not exist) class which works the same way as WebDriverWait.

推荐答案

上面提到的WebElementWait类:

The WebElementWait class as metioned above:

package org.openqa.selenium.support.ui;

import java.util.concurrent.TimeUnit;

import org.openqa.selenium.NotFoundException;
import org.openqa.selenium.WebElement;

public class WebElementWait  extends FluentWait<WebElement>  {
    public final static long DEFAULT_SLEEP_TIMEOUT = 500;

      public WebElementWait(WebElement element, long timeOutInSeconds) {
            this(element, new SystemClock(), Sleeper.SYSTEM_SLEEPER, timeOutInSeconds, DEFAULT_SLEEP_TIMEOUT);
      }

      public WebElementWait(WebElement element, long timeOutInSeconds, long sleepInMillis) {
            this(element, new SystemClock(), Sleeper.SYSTEM_SLEEPER, timeOutInSeconds, sleepInMillis);
      }

      protected WebElementWait(WebElement element, Clock clock, Sleeper sleeper, long timeOutInSeconds,
              long sleepTimeOut) {
            super(element, clock, sleeper);
            withTimeout(timeOutInSeconds, TimeUnit.SECONDS);
            pollingEvery(sleepTimeOut, TimeUnit.MILLISECONDS);
            ignoring(NotFoundException.class);
      }

}

与WebDriverWait相同，只是将 WebDriver 参数替换为 WebElement .

It's the same as WebDriverWait, except that the WebDriver argument is replaced with WebElement.

然后是isValid方法:

Then, the isValid method:

//import com.google.common.base.Function;
    //import org.openqa.selenium.TimeoutException;

public boolean isValid(WebElement e) {
    try {
        WebElementWait wait = new WebElementWait(e, 1);
        //@SuppressWarnings("unused")
        //WebElement icon = 
        wait.until(new Function<WebElement, WebElement>() {
                    public WebElement apply(WebElement d) {
                        return d.findElement(By
                                .xpath("./following-sibling::div[class='invalid-icon']"));
                    }
                });
        return false;
    } catch (TimeoutException exception) {
        return true;
    }
}

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