Unable to use the Page Object in a Test Method. (TestNG) - webdriver

Question

I m somebody who to new to Automation. I m currently learning Selenium Webdriver with JAVA along with Page Object Model pattern. When I experimenting with the few lines of code I got myself strucked at one point. I created a separate class file for the Page Elements which has the below code.
public class SamplePage {
WebDriver Driver;
public WebElement Gmail_Email_TextBox = Driver.findElement(By.xpath(".//*[#id='Email']"));
public WebElement Gmail_Email_Next_Button = Driver.findElement(By.xpath(".//*[#id='next']"));
public SamplePage(WebDriver Driver) { //This is a constructor.
System.out.println("Constructor");
this.Driver = Driver;
}
}
When try call the above page in another class I get java.lang.NullPointerException. Pls find the code below.
public class SampleTestMethod {
WebDriver Driver;
#BeforeMethod
public void BrowserLaunch() throws InterruptedException {
Driver = Browser.LaunchMozillaFirefox("https://accounts.google.com/ServiceLogin?continue=https%3A%2F%2Fmail.google.com%2Fmail%2F&service=mail&sacu=1&rip=1");
}
#Test
public void TestCase1() {
SamplePage Sample1 = new SamplePage(Driver);
Sample1.Gmail_Email_TextBox.click();
}
}
Pls clarify me on this. The constructor is not being called at all. This is what I have observed.

Answer 1

Class fields like Gmail_Email_TextBox and Gmail_Email_Next_Button are evaluated as null before constructor's call and never changed afterwards. That is why.
Simply put: initialize those fields in a different place.
You can add a #FindBy annotation to each of them and then just use PageFactory:
SamplePage samplePage = new SamplePage();
PageFactory.initElements(driver, samplePage);
Further info on this.
Follow naming conventions and use camelCase.
Instance variables are initialized before constructor calls.
Check this out to see it yourself:
public class Example {
private String instanceVariable;
private String anotherInstanceVariable = instanceVariable + " appended.";
public Example(String instanceVariable) {
this.instanceVariable = instanceVariable;
}
public static void main(String[] args) {
Example example = new Example("The first one");
System.out.println(example.anotherInstanceVariable);
}
}
instanceVariable is like your driver. anotherInstanceVariable is like any of your WebElements.