FindBy属性何时触发driver.FindElement? [英] when do FindBy attributes trigger a driver.FindElement?

问题描述

我的问题是:装饰有findby属性的Webelements是否在每次引用它们时调用findelement函数?如果没有，什么时候?

My question is: do webelements decorated with findby attributes call the findelement function upon each reference to them? If not, when?

使用List<的过程是什么? webelement>哪个也装饰过?当您引用列表或引用列表中的元素时，它会触发吗?

And what is the procedure with List< webelement > which is also decorated? Does it trigger when you reference the list, or when you reference an element inside that list?

我之所以问是因为，在某些情况下，我会遇到过时的元素异常，并且我想知道如何处理它们.

I'm asking because I have some situations where I'm getting stale element exceptions and I want to know how to deal with them.

推荐答案

WebElements的计算是惰性的.也就是说，如果您从不在PageObject中使用WebElement字段，则永远不会调用它的"findElement". 参考.

WebElements are evaluated lazily. That is, if you never use a WebElement field in a PageObject, there will never be a call to "findElement" for it. Reference.

如果不想每次WebDriver都查询元素，则必须使用@CacheLookup批注.

If don't want WebDriver to query the element each time, you have to use the @CacheLookup annotation.

我的问题的列表部分如何?

What about the list part of my question?

当您从列表中查询时，将触发findElements.说你有:

The findElements is triggered when you query from the list. Say you have:

@FindBy(xpath = "//div[@class=\"langlist langlist-large\"]//a")
private List<WebElement> list;

下面的代码对所有 trigger 的findElements进行采样:

Following code samples all trigger the findElements :

list.isEmpty();

WebElement element = list.get(0);

为

List<WebElement> newList = new ArrayList<WebElement>();
newList = list;

不会触发.

请检查LocatingElementListHandler类.我建议深入探讨答案.

Please check the LocatingElementListHandler class. I suggest diving into the source for answers.

您可能会发现PageFactory类中的以下代码注释很有帮助:

You may find this code comment from PageFactory class helpful:

/**
   * Instantiate an instance of the given class, and set a lazy proxy for each of the WebElement
   * and List<WebElement> fields that have been declared, assuming that the field name is also
   * the HTML element's "id" or "name". This means that for the class:
   * 
   * <code>
   * public class Page {
   *     private WebElement submit;
   * }
   * </code>
   * 
   * there will be an element that can be located using the xpath expression "//*[@id='submit']" or
   * "//*[@name='submit']"
   * 
   * By default, the element or the list is looked up each and every time a method is called upon it.
   * To change this behaviour, simply annotate the field with the {@link CacheLookup}.
   * To change how the element is located, use the {@link FindBy} annotation.
   * 
   * This method will attempt to instantiate the class given to it, preferably using a constructor
   * which takes a WebDriver instance as its only argument or falling back on a no-arg constructor.
   * An exception will be thrown if the class cannot be instantiated.
   * 
   * @see FindBy
   * @see CacheLookup
   * @param driver The driver that will be used to look up the elements
   * @param pageClassToProxy A class which will be initialised.
   * @return An instantiated instance of the class with WebElement and List<WebElement> fields proxied
   */

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