WebElement #getScreenShotAs(OutputType.File)无法正常工作

Question

我试图在Firefox浏览器代码中使用selenium webdriver 2.47.0版本中添加的WebElement#getScreenShotAs(OutputType.FILE)功能

public static void main(String[] args) throws IOException {
        WebDriver driver=new FirefoxDriver();
        driver.manage().window().maximize();
        driver.get("http://automationpractice.com/index.php");
        WebElement element=driver.findElement(By.cssSelector("a[title='Contact Us']"));
        System.out.println(element.getText());
        element.getScreenshotAs(OutputType.FILE);
        File destination=new File("Image.png");
        FileUtils.copyFile(null, destination);
    }

..但我得到以下异常:

Contact us
Exception in thread "main" org.openqa.selenium.UnsupportedCommandException: Unrecognized command: GET /session/e796089b-1d64-4590-9157-a0716a57e399/screenshot/%7B4329461b-5e9c-4f8b-b589-ddc1af1d55a6%7D
Command duration or timeout: 16 milliseconds
Build info: version: '2.52.0', revision: '4c2593cfc3689a7fcd7be52549167e5ccc93ad28', time: '2016-02-11 11:22:43'
System info: host: 'mrunal-laptop', ip: '192.168.56.1', os.name: 'Windows 7', os.arch: 'amd64', os.version: '6.1', java.version: '1.8.0_45'
Driver info: org.openqa.selenium.firefox.FirefoxDriver
Capabilities [{applicationCacheEnabled=true, rotatable=false, handlesAlerts=true, databaseEnabled=true, version=41.0.2, platform=WINDOWS, nativeEvents=false, acceptSslCerts=true, webStorageEnabled=true, locationContextEnabled=true, browserName=firefox, takesScreenshot=true, javascriptEnabled=true, cssSelectorsEnabled=true}]
Session ID: e796089b-1d64-4590-9157-a0716a57e399
    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:422)
    at org.openqa.selenium.remote.ErrorHandler.createThrowable(ErrorHandler.java:206)
    at org.openqa.selenium.remote.ErrorHandler.throwIfResponseFailed(ErrorHandler.java:158)
    at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:678)
    at org.openqa.selenium.remote.RemoteWebElement.execute(RemoteWebElement.java:327)
    at org.openqa.selenium.remote.RemoteWebElement.getScreenshotAs(RemoteWebElement.java:447)
    at thirdsession.GetProperties.main(GetProperties.java:20)

Answer 1

对于错误的真正原因是,许多/大多数的webdriver实现实际上不支持基于元素的屏幕截图,尽管WebElement延长TakesScreenshot 由于2.47.0.也许有一天这会改变.

如果你想要截图,你需要在整个浏览器级别进行,在这种情况下 - 正如其他答案所有 - 你需要传递WebDriver实例.

File ssFile = ((TakesScreenshot)(driver)).getScreenshotAs(OutputType.FILE);

严格来说,您可能应该执行以下操作,因为并非所有驱动程序都保证支持屏幕截图,例如HtmlUnitDriver.

if (!(getDriver() instanceof TakesScreenshot)) {
    File ssFile = ((TakesScreenshot)(driver)).getScreenshotAs(OutputType.FILE);
    // ...
}

有单元素截图的替代解决方案,但它们不可避免地涉及裁剪完整的浏览器截图.例如,请参阅:https://stackoverflow.com/a/13834607/954442

更新:只是为了澄清这不是一个错误,虽然元素截图是W3C WebDriver规范的一部分,但不同的浏览器具有不同级别的合规性/覆盖率,据我所知,此功能仅受Microsoft Edge支持.