Find Element By Image Locator Strategy in Appium


      Picking the right locator strategy during mobile automation helps to stabilize the automation flow. One of my previous articles, I have already mentioned the selection of the right locator strategy. There I have mentioned about -image selector.

    The -image locator strategy is pretty nifty. Supported on all platforms and drivers, you can pass an image file to Appium and it will try to locate the matching elements on the screen. This supports fuzzy matching and certainly has its applications, but you should only use it when the other locator strategies aren’t working. It may not always behave deterministically, which means it can be a source of test flakiness. Also, unless you have a special code editor, they may be a little more difficult to work with and maintain. Of course, visual UI changes will always break -image selectors, whereas the other selectors only break when the element hierarchy changes. In this article, I would like to explain about find elements By Image. 

     The Appium team finally decided to bite the bullet and support a small set of visual detection features, which are available as of Appium 1.9.0 version and above. An image element looks to your client code exactly like any other element, except that you’ve found it via a new -image locator strategy. Instead of a typical selector (like “foo”), the strings used with this new locator strategy are Base64-encoded image files. The image file used for a particular find action represents a template image that will be used by Appium to match against regions of the screen in order to find the most likely occurrence of the element you’re looking for.

     Suppose you have a scenario like, click on a particular image from your gallery and validate it.  None of the images have any identifying information in the UI tree, and their order changes every time we load the view, so we can’t hardcode an element index if we want to tap a particular image. Find-by-image to the rescue. Actually using this strategy is the same as finding an element using any other strategy:

WebElement element = driver.findElementByImage(base64EncodedImageFile);

     Of course, for this to work we have to have a Base64-encoded version of your image file. In Java 8 this is pretty straightforward:

// consider that you have a File called myImageFile.You can fetch image path //refImgUrl using ClassLoader class
File myImageFile = Paths.get(refImgUrl.toURI()).toFile();

     One another great thing is that finding elements by image supports both implicit and explicit wait strategies, so your tests can robustly wait until your reference image matches something on the screen:

By image = MobileBy.image(base64EncodedImageFile);
new WebDriverWait(driver, 10)

     By using the above simple code snippet you can easily navigate to the gallery, click on your particular image, and validate it. Try to use the above find element by image locator strategy in your Appium automation script and enjoy automation.

Reference: Appium Pro

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