In one of my ecommerce Android App that displays products and product details by clicking on a particular product the user can go back to the list of products from the product detail view by clicking on the Back button on their device or by clicking on the back button on top of the app located on the top left corner of the app. This is a basic navigation drawer UI pattern for Android.
Going back to the products list through the Toolbar Back icon
Going back to the products list through the Back button of Device
The user experience is broken in going back to the products list through the Toolbar back icon. It reloads the products list again after going back from the product detail. This isn't what we want do we? And certainly this is not what your users expect.
In order to solve this default behavior of the back icon in the toolbar for your use case we have to know why this is happening. This is happening because the back icon in the toolbar will call the onCreate method of the products list activity again. While pressing the Back button of the device will only show the product list (which is what we want for this scenario).