Design a user$-$friendly and simple Calculator app in Android that has at least the following functionalities: a$)$ Two input fields for entering two integers from the user b$)$ Four buttons for performing addition, subtraction, multiplication, or division. When the user clicks the button, it should perform a particular mathematical operation. c$)$ For some buttons, add the click event listener in the XML$/$Java files while for the other buttons, add the click event listener only in the java files. d$)$ A text field for displaying the result of the mathematical operation. e$)$ Performs validation i$.$e$.,$ making sure that the entered user inputs are numbers, and they aren$$t empty. f$)$ In case of validation or other errors, the app displays a toast message with the appropriate error.