以东方财富网登录页面为例：
在查找元素过程中，直接通过id或者xpath等找不到元素，查看页面源代码发现元素是属于iframe里，例如：
<div class="wrap_login">
<iframe class="frame_login" src="https://exaccount.eastmoney.com/home/login?request=%7b%22agentPageUrl%22%3a%22https%3a%2f%2fpassport.eastmoney.com%2fpub%2fLoginAgent%22%2c%22redirectUrl%22%3a%22http%3a%2f%2fwww.eastmoney.com%2f%22%2c%22callBack%22%3a%22LoginCallBack%22%2c%22redirectFunc%22%3a%22PageRedirect%22%2c%22data%22%3a%7b%22domainName%22%3a%22passport.eastmoney.com%22%2c%22deviceType%22%3a%22Web%22%2c%22productType%22%3a%22UserPassport%22%2c%22versionId%22%3a%220.0.1%22%7d%7d"></iframe>
</div>
以下为了定位到iframe里面元素，有2种方法：
方法一：单独打开iframe网址，直接定位。
@Test
public void loginTest() throws InterruptedException { System.setProperty("webdriver.firefox.bin", "D:\\Program Files\\Mozilla Firefox\\firefox.exe");
WebDriver driver = new FirefoxDriver();
driver.get("https://exaccount.eastmoney.com/home/login?request=%7b%22agentPageUrl%22%3a%22https%3a%2f%2fpassport.eastmoney.com%2fpub%2fLoginAgent%22%2c%22redirectUrl%22%3a%22http%3a%2f%2fwww.eastmoney.com%2f%22%2c%22callBack%22%3a%22LoginCallBack%22%2c%22redirectFunc%22%3a%22PageRedirect%22%2c%22data%22%3a%7b%22domainName%22%3a%22passport.eastmoney.com%22%2c%22deviceType%22%3a%22Web%22%2c%22productType%22%3a%22UserPassport%22%2c%22versionId%22%3a%220.0.1%22%7d%7d");
driver.manage().window().maximize();
Thread.sleep(3000);
driver.findElement(By.id("txt_account")).sendKeys("ycyzharry");
driver.findElement(By.id("txt_pwd")).sendKeys("password");
driver.findElement(By.id("btn_login")).click();
} }
方法二：先切换到iframe，再进行定位。
@Test
public void clickButtonTest() throws InterruptedException { System.setProperty("webdriver.firefox.bin", "D:\\Program Files\\Mozilla Firefox\\firefox.exe");
WebDriver driver = new FirefoxDriver();
driver.get("https://passport.eastmoney.com/pub/login?backurl=http%3A//www.eastmoney.com/");
driver.manage().window().maximize();
Thread.sleep(3000); WebElement iframe = driver.findElement(By.className("frame_login"));
driver.switchTo().frame(iframe);
driver.findElement(By.id("txt_account")).sendKeys("ycyzharry");
driver.findElement(By.id("txt_pwd")).sendKeys("password");
driver.findElement(By.id("btn_login")).click();
} }
值得注意的是，如果iframe有id时，切换iframe时把id作为参数直接传入
driver.switchTo().frame("id");
以上示例中，iframe没有id，只有class="frame_login"，所以我们需要先通过classname定位到iframe元素，再把该元素作为参数传入。
例如，如果要跳出iframe，可以使用以下方法：
driver.switchTo().defaultContent();