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    Question Detecting collision


    I am asked to do the following:

    Write a method in the Board class that takes a row and column index and a two-dimensional array as parameters, and checks to see that the non-zero entries of the given array correspond to empty positions on the grid, assuming that the given array's upper left were positioned at the given row and column. You'll use this to determine if a piece can move into a given position.

    So I have a Piece object and two variable currentX and currentY. I am assuming those will be passed into the method described above. currentX and currentY represent the top corner of the shapes. Now, how do I implement collision detection? I think we need to have 2 for loops and find the indexes of the shape array that contains 1. After that, I might have to create an array of the same size as shape array and then do two for loops to see if there is a collision if the shape moves below.

    So I need to have 3 methods implementing the same logic. One for move right, another for move left and another for move down, right? Isn't there a simpler method?


    Code:

    Code:
    import java.awt.*;
    
    public class Board extends Grid {
    	public static final int COLUMNS = 16;
    	public static final int ROWS = 32;
    	public static final Color BLUE = new Color(0,0,128,40);
    	
    	public Board() {
    		super(new int[ROWS][COLUMNS]);
    		setSize(COLUMNS*Tetris.SQUARE_SIZE,
    				ROWS*Tetris.SQUARE_SIZE);
    	}
    	
    	public void paintComponent(Graphics g) {
    		super.paintComponent(g);
    		g.setColor(BLUE);
    		paintStripes(g);
    	}
    	
    	void paintStripes(Graphics g) {
    		for (int i = 0; i < COLUMNS; i += 4) {
    			g.fillRect(i*Tetris.SQUARE_SIZE,0,
    				Tetris.SQUARE_SIZE*2,Tetris.SQUARE_SIZE*ROWS);
    		}
    	}
    	
    
    }
    Code:
    Code:
    public class PieceFactory {
    
    	public static final int[][] L1 =
    		{{1,1,0,0},
    		 {0,1,0,0},
    		 {0,1,0,0},
    		 {0,0,0,0},
    		};
    
    	public static final int[][] L2 =
    		{{0,1,0,0},
    		 {0,1,0,0},
    		 {1,1,0,0},
    		 {0,0,0,0},
    		};
    
    	public static final int[][] T =
    		{{0,1,0,0},
    		 {1,1,0,0},
    		 {0,1,0,0},
    		 {0,0,0,0},
    		};
    
    	public static final int[][] BOX =
    		{{1,1,0,0},
    		 {1,1,0,0},
    		 {0,0,0,0},
    		 {0,0,0,0},
    		};
    
    	public static final int[][] BAR =
    		{{1,1,1,1},
    		 {0,0,0,0},
    		 {0,0,0,0},
    		 {0,0,0,0},
    		};
    
    	public static final int[][] STEP1 =
    		{{1,0,0,0},
    		 {1,1,0,0},
    		 {0,1,0,0},
    		 {0,0,0,0},
    		};
    
    	public static final int[][] STEP2 =
    		{{0,1,0,0},
    		 {1,1,0,0},
    		 {1,0,0,0},
    		 {0,0,0,0},
    		};
    
    	public static final int[][][] SHAPES = {L1,L2,T,BOX,BAR,STEP1,STEP2};
    
    	public static Piece createPiece() {
    		int[][] s = SHAPES[(int) (Math.random()*SHAPES.length)];
    		switch ((int) (Math.random()*10)) {
    			case 0:
    			case 1:
    			case 2:
    			case 3:
    			default: return new Piece(s);
    		}
    
    
    	}
    
    
    
    
    }
    Code:
    Code:
    import javax.swing.*;
    import java.awt.*;
    import java.awt.event.*;
    
    public class Tetris extends JFrame implements KeyListener {
    	public static final int SQUARE_SIZE = 10; // 10 by 10 pixels
    
    	static Board board;
    	static Tetris game;
    
    	JPanel mainPanel;
    	public Piece currentPiece;
    	int score = 0;
    	JButton scoreButton;
    
    	public Tetris() {
    		super("Tetris");
    		game = this;
    		Container pane = getContentPane();
    		pane.setLayout(new BorderLayout());
    
    		scoreButton = new JButton("0");
    		scoreButton.setEnabled(false);
    		pane.add(scoreButton,BorderLayout.NORTH);
    
    		board = new Board();
    		mainPanel = new JPanel();
    		mainPanel.setLayout(null);
    		mainPanel.add(board);
    		mainPanel.setPreferredSize
    			(new Dimension(Board.COLUMNS*SQUARE_SIZE,
    						   Board.ROWS*SQUARE_SIZE));
    		pane.add(mainPanel);
    
    		addKeyListener(this);
    		addWindowListener(new WindowAdapter() {
    			public void windowClosing(WindowEvent we) {
    				System.exit(0);
    			}
    		});
    		pack();
    		show();
    		setResizable(false);
    	}
    
    
    	public void addToScore(int v) {
    		score += v;
    		scoreButton.setText(""+score);
    	}
    
    	public int getScore() {
    		return score;
    	}
    
    	static Board getBoard() {
    		return board;
    	}
    
    	static Tetris getGame() {
    		return game;
    	}
    
    	static void sleep(int milliseconds) {
    		try {
    			Thread.sleep(milliseconds);
    		} catch (InterruptedException ie) {
    		}
    	}
    
    	public static void main(String[] args) {
    		Tetris game = new Tetris();
    		while (true) {
    			game.dropPiece();
    		}
    	}
    
    	void dropPiece() {
    		currentPiece = PieceFactory.createPiece();
    		mainPanel.add(currentPiece);
    		currentPiece.repaint();
    		currentPiece.fall();
    		//mainPanel.remove(currentPiece);
    		board.repaint();
    		addToScore(1);
    	}
    
    	public void keyPressed(KeyEvent event) {
    		int key = event.getKeyCode();
    		switch (key) {
    		case KeyEvent.VK_UP:  // up arrow
    		case KeyEvent.VK_KP_UP:
    			currentPiece.rotateCounterclockwise();
    			break;
    		case KeyEvent.VK_DOWN:  // down arrow
    		case KeyEvent.VK_KP_DOWN:
    			currentPiece.rotateClockwise();
    			break;
    		case KeyEvent.VK_LEFT:  // left arrow
    		case KeyEvent.VK_KP_LEFT:
    			currentPiece.moveLeft();
    			break;
    		case KeyEvent.VK_RIGHT:  // right arrow
    		case KeyEvent.VK_KP_RIGHT:
    			currentPiece.moveRight();
    			break;
    		case KeyEvent.VK_SPACE:  //  space bar
    			currentPiece.drop();
    		}
    	}
    
    	public void keyReleased(KeyEvent arg0) {
    	}
    
    	public void keyTyped(KeyEvent arg0) {
    	}
    
    
    }
    Code:

    Code:
    public class Piece extends Grid {
    	int currentX;     // current X location on the board
    	double currentY;  // current Y location on the board
    
    
    	public Piece(int shape[][]) {
    		super(shape);
    		currentX = 7;
    		currentY = 2;
    		updateLocation();
    	}
    
    	public Piece(int shape[][], currentX, currentY) {
    		super(shape);
    		this.currentX = currentX;
    		this.currentY = currentY;
    		updateLocation()
    	}
    
    
    
    	void updateSize() {
    		setSize(Tetris.SQUARE_SIZE*getColumns(),
    				Tetris.SQUARE_SIZE*getRows());
    	}
    
    	void updateLocation() {
    		setLocation(Tetris.SQUARE_SIZE*currentX,
    					(int) (Tetris.SQUARE_SIZE*currentY));
    	}
    
    	synchronized void moveDown() {
    
    	}
    
    	synchronized void moveLeft() {
    		currentX--;
    		updateLocation();
    	}
    
    	synchronized void moveRight() {
    		currentX++;
    		updateLocation();
    	}
    
        synchronized void rotateClockwise() {
        	int x = currentX;
        	int y = currentY;
    
        	currentPiece = new Piece(s, x, y);
    
        	updateLocation();
        }
    
    
    
    
    	synchronized void rotateCounterclockwise() {
    	}
    
    	void fall() {
    		// replace the following by your code
    		Tetris.sleep(2000);
    	}
    
    	synchronized void drop() {
    		currentY++;
    		updateLocation();
    	}
    
      public static int [][] multiplyMatrix(int [][] m1)
      {
      		int [][] m2 =
    		{{0,0,0,1},
    		 {0,0,1,0},
    		 {0,1,0,0},
    		 {1,0,0,0},
    		};
    
    
        int[][] result = new int[4][4];
    
        // multiply
        for (int i=0; i<4; i++)
          for (int j=0; j<4; j++)
            for (int k=0; k<4; k++)
            if (m1[i][k] * m2[k][j] > 0)
            {
            	result[i][j] = 1;
            }
            else
            {
            	result[i][j] = 0;
            }
    
    
        return result;
      }
    
        }
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    Code:
    void fall(Board board) {
     
    		int [][] a = getContents();
    		int [][] b = board.getContents();
     
    		while(Board.legalDown(currentX, currentY, a, a) && Board.isNotOutOfBoundDown(currentX, currentY, a, a))
    		{
    		currentX--;
    		updateLocation();
        	updateSize();
    		}
     
    		Tetris.sleep(2000);
    	}
    error: method legalDown in class Board cannot be applied to given types;

    error: method isNotOutOfBoundDown in class Board cannot be applied to given types;


    Code:
    public static boolean legalDown(int currentX, int currentY, int[][] board, int[][] shape)
    
    public static boolean isNotOutOfBoundDown(int currentX, int currentY, int[][] board, int[][] shape)
    Code:
    	public int[][] getContents()
    	{
    		return contents;
    	}
    What the?? I don't get it...

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