How to get all UI Elements fast - appium

Question

I have an arbitrary app open (can be either android or ios) and I want to get all elements from the UI.
The easy way would be:
appiumWebDriver.findElements(By.xpath("//*")) // this works and returns elements but is slow
However, this is slow and discouraged. Using By.className or other platform dependent strategies would be faster. However, I am not sure how to write a wildcard selector otherwise.
appiumWebDriver.findElements(By.className("*")) // this does not work and returns 0 elements
I would not mind having to differentiate between iOS or Android apps and writing specific code here, but I want a fast and reliable way to get all displayed elements.

Answer 1

The fastest way is the driver.getPageSource() command.
I did some speed tests at my end.
For Android, driver.getPageSource() can be 3x to 6x times faster than using XPath. For the demo app that I used, it took around 0.2 seconds to fetch the page source and around 0.3 to 0.6 seconds to fetch all the elements using XPath.
For iOS, driver.getPageSource() can be 10x to 15x faster than XPath or Predicate Strings. For the demo app that I used, it took around 1-3 seconds to fetch the page source and around 20-30 seconds to fetch the elements using XPath or Predicate String. Predicate String is little bit faster than XPath though.
Two things to note:
Irrespective of what method you use, for iOS, it would give all the elements present on the page. For Android, it would give only those elements that are visible on the screen. If the page is a scrollable page with more elements below the screen, those will not be fetched. You will need to scroll down and then run the command again to fetch these elements.
getPageSource() would give you the XML as a String. You can then use any XML parser to parse it and use it for your purpose.
Hope this helps.
Here's the code that I used to test this for iOS and Android.
public static void main(String[] args) throws Exception {
AppiumDriver driver;
// -> Initialize Android driver
driver = CreateDriverSession.initializeDriver("Android");
driver.findElement(AppiumBy.accessibilityId("Views")).click();
long time1 = System.currentTimeMillis();
driver.getPageSource();
long time2 = System.currentTimeMillis();
System.out.println("GET PAGE SOURCE TIME IN MILLIS" + (time2 - time1));
time1 = System.currentTimeMillis();
driver.findElements(AppiumBy.xpath("//*"));
time2 = System.currentTimeMillis();
System.out.println("XPATH TIME IN MILLIS" + (time2 - time1));
// -> Initialize iOS driver
driver = CreateDriverSession.initializeDriver("iOS");
time1 = System.currentTimeMillis();
String page = driver.getPageSource();
time2 = System.currentTimeMillis();
System.out.println("GET PAGE SOURCE TIME IN MILLIS" + (time2 - time1));
time1 = System.currentTimeMillis();
List<WebElement> elementsUsingXPath = driver.findElements(AppiumBy.xpath("//*"));
time2 = System.currentTimeMillis();
System.out.println("XPATH TIME IN MILLIS" + (time2 - time1));
time1 = System.currentTimeMillis();
List<WebElement> elementsUsingPredicateString = driver.findElements(AppiumBy.iOSNsPredicateString("TRUEPREDICATE"));
time2 = System.currentTimeMillis();
System.out.println("PREDICATE STRING TIME IN MILLIS" + (time2 - time1));
System.out.println("PAGE SOURCE = ");
System.out.println(page);
System.out.println("ELEMENTS USING XPATH = ");
for (WebElement element : elementsUsingXPath) {
System.out.println(element.getText());
}
System.out.println("ELEMENTS USING PREDICATE STRING = ");
for (WebElement element : elementsUsingPredicateString) {
System.out.println(element.getText());
}
}

Answer 2

platform specific code is required. For iOS you can use:
appiumWebdriver.asInstanceOf[IOSDriver].findElements(AppiumBy.iOSNsPredicateString("TRUEPREDICATE"))