How to select options of a JAVA SCRIPT popup on android?

I am able to select a text on a page on the android native app using
new TouchAction(driver).longPress(driver.findElementByName("), 2000).perform();
After selecting the element a javascript popup displayed with some options to select.
i am unable to select those options .
also this popup not displaying on the UIAUTOMATOR also.
Also using
Alert alert = driver.switchTo().alert();
i am getting this error message.
Exception in thread “main” org.openqa.selenium.WebDriverException: Not yet implemented. Please help us: (WARNING: The server did not provide any stacktrace information)
Command duration or timeout: 32 milliseconds
Please suggest.