how to wait for the second window to load completely

Question

I click a button from parent window and it loads a viewer in the new(child) window, then i do some action in the second window. Here before loading of my second window itself, the script tries to do some action and it fails. If i put Thred.sleep it goes successfully. But i do not want to use thread.sleep. Is there any way we can do to wait for SECOND/CHILD window to load its page completely. Here my second window(browser) is a PDF kind of viewer. Below is the code i tried.

WebElement row = ele.findElement(By.cssSelector("tr[data-ri=\"0\"]"));
row.findElement(By.className("ui-selection-column")).click();
browser.findElement(By.id("frmResults:btnViewer")).click();

Thread.sleep(5000);

Set<String> AllWindowHandles = browser.getWindowHandles();
String window1 = (String) AllWindowHandles.toArray()[0];
scenario.write("Currently in Parent Window = "+ AllWindowHandles.toArray()[0]);
scenario.write(browser.getCurrentUrl());
scenario.write(browser.getTitle());

String window2 = (String) AllWindowHandles.toArray()[1]; // out of bounds error thrown here

scenario.write("Switching to Child (Viewer) window = "+ AllWindowHandles.toArray()[1]);
browser.switchTo().window(window2);
scenario.write(browser.getCurrentUrl());
scenario.write(browser.getTitle());
WebElement viewer = browser.findElement(By.id("outerDiv"));
assertThat(viewer.isDisplayed()).isTrue();
//browser.close();

scenario.write("Again Switching back to Parent window = "+ AllWindowHandles.toArray()[0]);
browser.switchTo().window(window1);
scenario.write(browser.getCurrentUrl());
scenario.write(browser.getTitle());

Updated

I get the error when i try to get the child window number on this line.

String window2 = (String) AllWindowHandles.toArray()[1];

Error:

java.lang.ArrayIndexOutOfBoundsException: 1
        at Steps.Steps.verify_the_test_records_are_displayed_in_the_results_table_in_Search_Results_page(Steps.java:115)
        at ?.Then Verify the test records are displayed in the results table in Search Results page(Test.feature:10)

[ERROR] Tests run: 1, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 30.552 s <<< FAILURE! - in Runner.TestRunner
[ERROR] feature(Runner.TestRunner)  Time elapsed: 29.389 s  <<< FAILURE!
cucumber.runtime.CucumberException: java.lang.ArrayIndexOutOfBoundsException: 1
Caused by: java.lang.ArrayIndexOutOfBoundsException: 1

Answer 1

Instead of thread.sleep() , you can use the ExpectedConditions class to add a targeted explicit wait on the number of expected windows :

import org.openqa.selenium.support.ui.WebDriverWait;
import static org.openqa.selenium.support.ui.ExpectedConditions.numberOfWindowsToBe;
// we need the above using statements to use WebDriverWait and ExpectedConditions

// first wait for number of windows to be 2:
WebDriverWait wait = new WebDriverWait(browser, 10);
wait.until(ExpectedConditions.numberOfWindowsToBe(2)));

// switch to a new window
String window2 = (String) AllWindowHandles.toArray()[1];
scenario.write("Switching to Child (Viewer) window = "+ AllWindowHandles.toArray()[1]);
browser.switchTo().window(window2);

// wait on some element on the page to be fully loaded
wait.until(ExpectedConditions.visibilityOfElementLocated(By.id("outerDiv")));

ExpectedConditions should wait on 2 windows to exist before calling String window2 = (String) AllWindowHandles.toArray()[1]; -- this should ensure browser.getWindowHandles() returns 2 before attempting to switch to the second window.