Android : How to animate Button Text in Android 4?

in the name of God hello,

i want to play a animation for text in my button and background not play animation. how i can do this?

                Animation fadeIn = new AlphaAnimation(0, 1);
            fadeIn.setInterpolator(new AccelerateInterpolator()); //and this
           // fadeIn.setStartOffset(500);
            fadeIn.setDuration(time);
            tmg_y.setAnimation(fadeIn);

i am sorry for bad speak English.