I think most of the answers here are over-engineered. The way i did it is through 2 helper methods, the first to wait for an element based on any selector; and the second to take a screenshot of it.
Note: We cast the WebElement to a TakesScreenshot instance, so we only capture that element in the image specifically. If you want the full page/window, you should cast driver instead.
WebDriver driver = new FirefoxDriver(); // define this somewhere (or chrome etc)
public <T> T screenshotOf(By by, long timeout, OutputType<T> type) {
return ((TakesScreenshot) waitForElement(by, timeout))
.getScreenshotAs(type);
}
public WebElement waitForElement(By by, long timeout) {
return new WebDriverWait(driver, timeout)
.until(driver -> driver.findElement(by));
}
And then just screenshot whatever u want like this :
long timeout = 5; // in seconds
/* Screenshot (to file) based on first occurence of tag */
File sc = screenshotOf(By.tagName("body"), timeout, OutputType.FILE);
/* Screenshot (in memory) based on CSS selector (e.g. first image in body
who's "src" attribute starts with "https") */
byte[] sc = screenshotOf(By.cssSelector("body > img[href^='https']"), timeout, OutputType.BYTES);