selenium无法定位到QQ邮箱登录页面的输入框元素和登录按钮元素-解决方法

问题如下：

代码如下：

package TestNG1;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.support.FindBy;
import org.openqa.selenium.support.PageFactory;
import org.testng.annotations.Test;

public class TestDemo1 {

@FindBy(id="u")
public WebElement Username;
@FindBy(id="p")
public WebElement Password;
@FindBy(id="login_button")
public WebElement Loginbutton;

public TestDemo1(WebDriver driver){
PageFactory.initElements(driver,this);
}
}

package TestNG1;

import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.testng.annotations.BeforeMethod;
import org.testng.annotations.Test;

public class TestDemo2 {
WebDriver dr;
String url="https://en.mail.qq.com/cgi-bin/loginpage";
@BeforeMethod
public void BeforeMethod(){
System.setProperty("webdriver.firefox.bin", "D:\\programfile\\firefox\\firefox.exe");
dr=new FirefoxDriver();
dr.get(url);
dr.manage().window().maximize();
}
@Test
public void f() {

TestDemo1 test=new TestDemo1(dr);
test.Username.sendKeys("XXXXXX");
test.Password.sendKeys("XXXXXX");
test.Loginbutton.click();
}
}

页面报错：

org.openqa.selenium.NoSuchElementException: Unable to locate element: {"method":"id","selector":"u"}


修改为：

package TestNG1;

public class TestDemo2 {
WebDriver dr;
String url="https://en.mail.qq.com/cgi-bin/loginpage";
@BeforeMethod
public void BeforeMethod(){
System.setProperty("webdriver.firefox.bin", "D:\\programfile\\firefox\\firefox.exe");
dr=new FirefoxDriver();
dr.get(url);
dr.manage().window().maximize();
}
@Test
public void f() {
WebElement frame=dr.findElement(By.id("login_frame")); // 添加frame元素
dr.switchTo().frame(frame);
TestDemo1 test=new TestDemo1(dr);
test.Username.sendKeys("XXXXXXX");
test.Password.sendKeys("XXXXXXX");
test.Loginbutton.click();
}
}