How can I set the following two properties for a text field in Android: 

(**Property 1**) How can I set a text field that contains some text like "Enter a number" but when it is clicked the text field automatically becomes empty?

(**Property: 2**) Suppose I have two text fields in my application. My *first* text field only accepts integers and the *second* text field accepts text like "name, address" etcetera. But by mistakenly I enter some text like "apple" or "ball" in my first text field that only accepts numbers. 

How can I set my *first* text field so that when I click on the *second* text field my *first* text field should show a toast message or change the color of inputed data to indicate invalid input?