How to make a button bigger when pressed? (Android Studios)

I'm working on an app in Android studios and would like my customised button to get bigger when pressed and go back to the default defined state when released. I wrote an xml file to define my button but it didn't work. Here's my xml file for the custom button:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/play_button_pressedhdpi"
        android:state_pressed="true" />
    <item android:drawable="@drawable/play_button_defaulthdpi"
        android:state_focused="true" />
    <item android:drawable="@drawable/play_button_defaulthdpi" />
</selector>

This doesn't seem to work. Any help would be appreciated.

Edit:

I just tried the following code as mentioned in the first answer below:

button1.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {

            RelativeLayout.LayoutParams lp = (RelativeLayout.LayoutParams) v.getLayoutParams();
            if (event.getAction() == MotionEvent.ACTION_DOWN)
            {
                //sendMessage("Key1\n");
                lp.width = 200;
                lp.height = 200;
                button1.setLayoutParams(lp);
            }

            if(event.getAction() == MotionEvent.ACTION_UP) {
                lp.width=90;
                lp.height=90;
                button1.setLayoutParams(lp);
            }
            return false;
        }
    });

This makes sense but didn't work for some reason.

Any help would be appreciated...

Solution

I was finally able to solve the problem. I created two separate images of two different sizes and used the setOnTouchListener() to assign the appropriate image to the button for each of the states ACTION_DOWN and ACTION_UP in the following manner:

button1.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            if (event.getAction() == MotionEvent.ACTION_DOWN)
            {
                float x = (float) 1.25;
                float y = (float) 1.25;

                button1.setScaleX(x);
                button1.setScaleY(y);
                button1.setBackgroundResource(R.drawable.blue_220);

                return true;
            }

            else if(event.getAction() == MotionEvent.ACTION_UP)
            {
                float x = 1;
                float y = 1;

                button1.setScaleX(x);
                button1.setScaleY(y);
                button1.setBackgroundResource(R.drawable.blue_206);

            }
            return false;
        }
    });

Result as desired.