Help with designing a small project

Question

I'm still relatively new to game design. I want to attempt to make a clone of the TI Calc game "Fall Down" (http://www.ticalc.org/archives/files/fileinfo/140/14064.html). It's an incredibly simple game overall, but I can't seem to figure out how to handle everything in an object oriented manner
So far in my design process, I have a Blackboard class (that extends JPanel) that's responsible for painting the game screen. The ball is represented by a Ball class that contains the location of the ball on the screen, as well as 3 functions to move the ball. I have a floor class that will represent one rising floor with a hole in it.
I've delegated moving the floors and ball upward toward the top of the screen to a Conveyer class.
I'm still left with one slight problem: to which class do I give the responsibilty of receiving keyboard input to update the position of the ball? I can't give it to the Ball object itself, because it's not aware of it's surroundings (and thus the Ball class can't know if it's okay to move left or right). Using the conveyer class would work, except it's already been delegated a large task of updating all objects. The Blackboard is already busy with painting to the screen.
What would be the most appropriate way to go about this?

Answer 1

I would assign the ball controlls to the main game class (game window or game applet) and send the new position to the ball itself. The main advantages are:
=> If you take the main class to be an Applet or some subclass of a Component (Frame, Window, Panel, JPanel... although I wouldn'd drag JavaX into it. The game should be perfectly doable with just standard AWT components) You can directly implement a KeyboardListener class that handles the keyboard imput and translates them to the ball position.
=> If you take a classic arcade approach allowing the ball ONE movement (left-right) per movement of the floors, you can use the same thread for the floor and ball. Locate the thread in the master clas and have it call the ball as well as the transporter.
The distribution of functions between the differnt classes would now be:
main FallDown class:
- an applet or Frame that implements the KeyListener classes
- On KeyListener.KeyEvent: set the desired movement of the ball to the new direction.
- implements main game thread: the thread continuously calls for a certain 'sleep' time and between each time takes a 'game turn' :
# calls the ball to move. The ball will move in the direction set beforehand by the key listeners
# calls the floor conveyor to move all the floors one level up
# checks if the ball crashed into the floor by comparing the current position of the ball with the current opening in the highest floor
# calls a 'repaint()' to redraw the game screen
- on Paint(Graphics g) or update(Graphics g)
# clears the screen in background color
# draws the ball by calling its own paint(Graphics g) function (passing the current graphics)
# draws the floors by calling the floor conveyor's paint(Graphics g) function (passing the current graphics)
Ball class
- contains a paint(g) function to paint the ball on the screen
- contains a setDirection function to set the desired direction upon a request of the main classes' keyboard listener
- contains an updatePosition() function to set the ball to its new position every time the main turn loop passes a new turn
- contains a getPosition() function that returns the position to the main class to check for colisions with the wall
FloorConveyor class:
- contains a paint(g) function to paint all the floors on the screen
- contains a moveUp() function to move the floors one position up every time the main turn loop passes a new turn (also initialize new floors on the bottom of the conveyor?)
- contains a getOpening() function to allow the main loop to compare the opening of the uppermost floor with the position of the ball
(Floor class:
- contains a paint(g) function to draw a floor
- contains a moveUp() function to move the floor one position up when requested by the conveyor
- contains a getOpening() function to pass this floor's opening to the floorconveyor
'Niklas