任何人都可以在Selenium中解释截图吗？

Question

WebDriver driver = new FirefoxDriver();

driver.get("http://www.google.com/");

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

// Now you can do whatever you need to do with it, for example copy somewhere
FileUtils.copyFile(scrFile, new File("c:\\tmp\\screenshot.png"));

可以告诉我的

File scrFile = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE) 

getScreenShotAsTakesScreenshot界面中的方法......

(TakesScreenshot)driver,它指的是什么？你能解释一下吗？

Answer 1

该WebDriver接口不包含该getScreenshotAs()方法,因为可能有一个webdriver无法截取屏幕截图 - 例如内存驱动程序根本不呈现页面,例如HtmlUnitDriver.

为了获得该方法,驱动程序必须实现TakesScreenshot接口,使其能够......好...截取屏幕截图.

因此,您必须以某种方式告诉程序您想截取屏幕截图,并且您绝对相信您可以这样做.这就是这个(TakesScreenshot)driver部分的用途.在Java中,它被称为强制转换,它实际上转换为"我知道这个driver实例能够截取屏幕截图,请将其转换为TakesScreenshot类型".

如果你的演员成功,一切都很好,driver对象将在运行时转换为一个实例TakesScreenshot.但是,如果您的演员表失败,那么您将获得一个ClassCastExcepion运行时.

一些例子:

// We already know this is ok, because FirefoxDriver implements (IS-A) TakesScreenshot.
WebDriver driver = new FirefoxDriver();
TakesScreenshot screenshottingDriver = (TakesScreenshot)driver;

// This will fail at run-time, because HtmlUnitDriver does not implement TakesScreenshot;
WebDriver driver = new HtmlUnitDriver();
TakesScreenshot screenshottingDriver = (TakesScreenshot)driver;

// You can use the `instanceof` operator to check:
if (driver instanceof TakesScreenshot) {
    // we can be sure we can take screenshots, the cast will be safe
    ((TakesScreenshot)driver).getScreenshotAs(...);
}