java - 使用 WebDriverWait Boolean 的 NullPointerException

Question

我有两个类，一个运行单击按钮等的方法。在页面上，有一个按钮被禁用，我有一个 WebDriverWait 来等待它通过检查属性“disabled”再次启用"已从 html 元素中删除。但是，当我运行测试时，我得到一个 nullPointerException。我想我知道它来自哪里，但在尝试解决它时遇到问题。

这是运行以执行操作的方法:

public void methodThatRuns(WebDriver driver) throws InterruptedException {
    properties.inputTxt(driver, "100");
    sundries.waitEnabledButton(driver, properties.nextButton(driver));
    properties.nextButton(driver).click();
}   

这是另一个类的 waitEnabledButton 方法，它调用等待:

public void waitEnabledButton(WebDriver driver, final WebElement btn) throws NullPointerException {
    WebDriverWait wait = new WebDriverWait(driver, 10);
    System.out.println("Starting the wait");
    try {
        wait.until(new ExpectedCondition<Boolean>(){
            public Boolean apply(WebDriver driver) {
                final String attribute = btn.getAttribute("disabled");
                if (attribute.equals(null)) {
                    return true;
                }
                else {
                    return false;
                }
            }
        });
    } catch (StaleElementReferenceException e) {
        System.out.println("The disabled attribute was destroyed successfully and the script can continue."); //using this as the attribute gets destroyed when the button is enabled which throws a staleElement exception
    } 
    System.out.println("Wait is over");
}

对此的任何帮助将不胜感激!

Answer 1

 if (attribute.equals(null)) {
    return true;
  }`

如果 attribute 为 null，则 .equals 调用将导致 NPE。尝试使用属性== null。