如何检查可能存在或不存在的元素的可见性？

Question

考虑这个网址：https://sfbay.craigslist.org/pen/apa/5759740929.html 单击“回复”按钮时，您将看到一个带有回复选项的弹出式窗口。 div可能有也可能没有电话号码和联系人姓名。

我为此制作了一些代码，我期望按照以下几点提到的工作。

1-如果单击了回复按钮，则等待回复选项弹出窗口可见。当弹出窗口可见时，查找任何电话号码并提取它们。

2-如果弹出窗口中没有数字，则不执行任何操作（因为此人不想分享他/她的电话号码。）

3-如果有人在弹出窗口未打开时尝试提取电话号码/姓名，则抛出一个运行时异常，表示没有点击回复按钮。

为什么在使用wait_for_reply_options_popup_to_be_visible（）时代码会失败，但在我使用时会传递： wait_for_calling_options_to_be_visible（）;

请帮助我理解原因并解决此问题。谢谢！

import org.junit.Before;
import org.junit.Test;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.support.ui.ExpectedConditions;
import org.openqa.selenium.support.ui.WebDriverWait;

import java.util.List;

import static Utils.extract_phone_numbers;

public class Temp {
    private static final WebDriver browser = new ChromeDriver();
    private static String url = "https://sfbay.craigslist.org/pen/apa/5759740929.html";

    private WebElement reply_btn;
    private String reply_btn_xpath = "//button[contains(concat(\" \", normalize-space(@class), \" \"), \" "
            + "reply_button" + " \")]";
    private By reply_btn_loc = By.xpath(reply_btn_xpath);


    private String reply_options_xpath = "//button[contains(concat(\" \", normalize-space(@class), \" \"), \" "
            + "reply_options" + " \")]";
    private By reply_options_loc = By.xpath(reply_options_xpath);

    private String call_options_xpath = "//b[contains(text(), 'call') or contains(text(), 'text')]";
    private By call_options_loc = By.xpath(call_options_xpath);

    public String phone_xpath = "following-sibling::ul/li";
    public By phone_loc = By.xpath(phone_xpath);

    @Before
    public void before_each_test() {
        browser.get(url);
        load_elements();
    }

    @Test
    public void get_phone_number() throws Exception {
        reply_btn.click();
        List<String> phones = get_calling_or_texting_options();
        System.out.println(phones);
    }

    private void load_elements() {
        reply_btn = new WebDriverWait(browser, 5).until(
                ExpectedConditions.presenceOfElementLocated(reply_btn_loc));
    }

    private void wait_for_calling_options_to_be_visible(){
        new WebDriverWait(browser, 5).until(ExpectedConditions.visibilityOfElementLocated(call_options_loc));
    }

    private void wait_for_reply_options_popup_to_be_visible(){
        new WebDriverWait(browser, 5).until(ExpectedConditions.visibilityOfElementLocated(reply_options_loc));
    }

    private List<String> get_calling_or_texting_options() {
        wait_for_reply_options_popup_to_be_visible();
        //wait_for_calling_options_to_be_visible();

        //Look for any element which contains call or text. Their sibling elements should have a number.
        List<WebElement> calling_options = browser.findElements(call_options_loc);
        WebElement calling_option = calling_options.get(0);

        if (calling_options.size() > 0) {
            //Get the sibling elements which contain phone numbers.
            WebElement phone_info = calling_option.findElement(phone_loc);

            //Remove all the extra text and extract only the phone number.
            List<String> phones = extract_phone_numbers(phone_info.getText());

            return phones;
        } else {
            String error = "Cannot get list of contact numbers! Please click the reply button first!";
            throw new RuntimeException(error);
        }

    }

}

堆栈跟踪：

org.openqa.selenium.TimeoutException: Timed out after 5 seconds waiting for visibility of element located by By.xpath: //button[contains(concat(" ", normalize-space(@class), " "), " reply_options ")].......
    at org.openqa.selenium.support.ui.WebDriverWait.timeoutException(WebDriverWait.java:80)
    at org.openqa.selenium.support.ui.FluentWait.until(FluentWait.java:261)
    at src.Temp.wait_for_reply_options_popup_to_be_visible(Temp.java:59)
    at src.Temp.get_calling_or_texting_options(Temp.java:63)
    at src.Temp.get_phone_number(Temp.java:45)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    .......
Caused by: org.openqa.selenium.NoSuchElementException: no such element
  (Session info: chrome=52.0.2743.116)
  (Driver info: chromedriver=2.9.248315,platform=Windows NT 6.1 SP1 x86_64) (WARNING: The server did not provide any stacktrace information)
Command duration or timeout: 9 milliseconds
For documentation on this error, please visit: http://seleniumhq.org/exceptions/no_such_element.html..........
............
*** Element info: {Using=xpath, value=//button[contains(concat(" ", normalize-space(@class), " "), " reply_options ")]}
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:408)
    at org.openqa.selenium.remote.ErrorHandler.createThrowable(ErrorHandler.java:206)
    ...........

Answer 1

WebElement个对象会告诉您它们是否通过内置函数可见/启用。

try{
    if(someElement.isDisplayed()) {
        // Do something...
    } else {
        // Do nothing...
    }
} catch (Exception e) {
    // Do nothing or handle exception...
}

另一方面，为了便于阅读，通常更好的做法是为功能提供更多......简洁的名称。即wait_for_reply_options_popup_to_be_visible()可能是waitForReplyOptions()。

编辑：直接从回购，建议你自己做方法进行检查，如下所示：

public static boolean isPresentAndDisplayed(final WebElement element) {
    try {
        return element.isDisplayed();
    } catch (NoSuchElementException e) {
        return false;
    }
}

Answer 2

您应该使用try catch创建一个方法，如上所述。但我建议不要使用isDisplay（）方法本身。相反，你应该使用FluentWait（）

制作一个方法

public WebElement visibilityWait(int timeInMilliSeconds, By by) {
    WebElement element = null;
    try {
        element = new FluentWait<>(webDriver).
            withTimeout(timeoutInMilliSeconds, TimeUnit.MILLISECONDS).
            pollingEvery(500, TimeUnit.MILLISECONDS).
            ignoring(NotFoundException.class).ignoring(NoSuchElementException.class).
            until(visibilityOfElementLocated(by));
    } catch (TimeoutException ex) {
        logger.warn("Ignore TimeoutException: ", ex.getMessage());
    }
    return element;
}

此方法仅在元素存在且可见时才返回该元素，如果它不返回null。您可以为您的案例设置超时，例如我不知道的15秒。

PS：顺便说一句，如果你的某个方法正在运行而另一个方法不正常，请再次检查你的xpath。没有看到网站就不能再说了什么:)。