Android MotionEvent for Touch being held down?

I have just started developing in Android and I am trying to make a very basic game where you have to move a bat along the bottom of the screen and catch items while avoiding bombs.

The problem I am having is I want the bat to move along the bottom of the screen when you hold your finger on the left or the right side of the screen.

Currently I can get the bat to move a few pixels across when the user touches the screen but I can not get it to keep moving until the user removes his finger from the screen.

Here is my (very) basic code so far :

package com.mattdrewery.supercatch;

import android.view.View;
import android.view.MotionEvent;
import android.content.Context;
import android.graphics.Canvas;

public class GameView extends View 
{
    private Catcher catcher;

    public GameView(Context context)
    {
        super(context);
        setFocusable(true);

        // Create the catcher
        catcher = new Catcher(context, R.drawable.catcher, 240, 250);
    }

    @Override
    protected void onDraw(Canvas canvas)
    {
        // Draw the catcher to the canvas
        canvas.drawBitmap(catcher.getImage(), catcher.getPosX(),  catcher.getPosY(), null);

        // Redraw the screen
        invalidate();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event)
    {
        // Get the action from the touch screen
        int eventAction = event.getAction();

        int X = (int) event.getX();
        int Y = (int) event.getY();

        // If the user presses on the screen....
        if (eventAction == MotionEvent.ACTION_DOWN)
        {
            catcher.moveLeft();
        }

        // Redraw the screen
        invalidate();

        return true;
    }
}

The catcher.moveLeft() method is as follows:

public void moveLeft()
    {
        posX -= 5;
    }

Any help with this matter would be greatly appreciated! :)