gui design - How to show a very important notification on the button itself which opens it?

I have 3 cases about the messages:

1. 
   

   No messages by Mr. X

   
   


2. 
   

   Some previous messages by Mr. X

   
   


3. 
   

   A new Message by Mr. X

   
   

I wanted to show these notifications on the button itself something like:

Case 1: No messages at all:

Case 2: Show previous messages:

Case 3: A new message:

I have no experience at UI. I'm a backend developer. Is this an acceptable design? Or is something better needed?

PS: This is a mobile application.

Answer

The label on the button must not change. This will confuse users. What you can do is keep the label constant and enhance the button with additional info accordingly. You may change the color, add additional graphics, but do not change the label.

I recommend the following :

Display a red circle on the button when new messages exists. In the circle put the number of new messages.

If it is very important to know the sender of the message then display the sender name of the first message.

I do not find the information "No previous messages" important so I recommend you to omit it. But if you must show the "no message state" then disable the button.