How to put graphics into a JViewport?

Question

Hi,
I'm trying to make a simple game, where a block can move around in a 30x30 grid with collision detection. So far, it works alright, but I want the window to hold only 10x10 and for the block that is moving to stay at the center while the painted background moves around. The program reads a .dat file to get the world.
So is there a way to use the background world Ive painted and put it into a viewport so that it will scroll when the keys are hit to move? Also I'd like to make the block stay at the center of the screen, unless it's at a corner.
Hopefully this makes sense and someone can help. Thanks.
Here's my code:
import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.io.*;
public class SmallWorld extends JPanel
                          implements KeyListener,
                                     ActionListener {
     //WORLD
     String[][] worldArray = new String[30][30];
     private static Color redBlock = new Color(255,0,0,255);
     private static Color whiteBlock = new Color(255,255,255,150);
     private static Color blackBlock = new Color(0,0,0,150);
     boolean keyUP = false;
     boolean keyDOWN = false;
     boolean keyLEFT = false;
     boolean keyRIGHT = false;
     //Starting coordinates
     int blockPositionX = 1;
     int blockPositionY = 1;
     JTextField typingArea;
     JViewport viewable;
    public SmallWorld() {
        super( );
          createWorld();     
        typingArea = new JTextField(20);
        typingArea.addKeyListener(this);
          typingArea.setEditable( false );
          add(typingArea);
     public void paintComponent(Graphics g) {
          super.paintComponent(g);
          String type = "";
          for (int i = 0; i < 30; i++) {
               for (int j = 0; j < 30; j++) {
                    type = worldArray[i][j];
                         if ( type.equals("1") )
                              g.setColor(redBlock);
                              g.fillRect( (j * 50),(i * 50),50,50 );
                         else {
                              g.setColor(whiteBlock);
                              g.fillRect( (j * 50),(i * 50),50,50 );          
          g.setColor(blackBlock);
          g.fillRect( (blockPositionX * 50),(blockPositionY * 50),50,50 );     
     //Get the world from the DAT file and translate it into a 2d array to be used by paintComponent
     public void createWorld() {
        String getData = null;
          int countRow = 0;
        try {
               FileReader fr = new FileReader("world.dat");
               BufferedReader br = new BufferedReader(fr);
               getData = new String();
               while ((getData = br.readLine()) != null) {
              if(countRow < 30) {
                    for (int i = 0; i < 30; i++) {
                         String temp = "" + getData.charAt(i);
                         worldArray[countRow] = temp;
                    countRow++;
} catch (IOException e) {
// catch possible io errors from readLine()
System.out.println("Uh oh, got an IOException error!");
e.printStackTrace();
     //Move Block around the world
     public void moveBlock() {
          Graphics g = this.getGraphics();
          Point pt = new Point();
          pt.x = blockPositionX * 50;
          pt.y = blockPositionY * 50;
          if (keyUP) {
               g.setColor(blackBlock);
          g.fillRect( (blockPositionX * 50),(blockPositionY * 50),50,50 );
          if (keyDOWN) {
               g.setColor(blackBlock);
          g.fillRect( (blockPositionX * 50),(blockPositionY * 50),50,50 );
          if (keyLEFT) {
               g.setColor(blackBlock);
          g.fillRect( (blockPositionX * 50),(blockPositionY * 50),50,50 );
          if (keyRIGHT) {
               g.setColor(blackBlock);
          g.fillRect( (blockPositionX * 50),(blockPositionY * 50),50,50 );
     //check for collisions with blocks
     public boolean checkCollision(int row, int col) {
          if ( worldArray[col][row].equals("1") ) {
               return true;
          else {
               return false;
//If key typed, put action here. none for now
public void keyTyped(KeyEvent e) {
/** Handle the key pressed event from the text field. */
public void keyPressed(KeyEvent e) {
updateView( e );
//If key released, put action here. none for now
public void keyReleased(KeyEvent e) {
/** Handle the button click. */
public void actionPerformed(ActionEvent e) {
     //Update the view of the window based on which button is pressed
     protected void updateView( KeyEvent e ) {
          //if UP is pressed
          if ( e.getKeyCode() == 38 ) {
               keyUP = true;
               if ( checkCollision( blockPositionX, blockPositionY - 1 ) == false ) {
                    blockPositionY = blockPositionY - 1;
                    this.repaint();
                    moveBlock();
               keyUP = false;
          //if DOWN is pressed
          if ( e.getKeyCode() == 40 ) {
               keyDOWN = true;
               if ( checkCollision( blockPositionX, blockPositionY + 1 ) == false ) {
                    blockPositionY = blockPositionY + 1;
                    this.repaint();
                    moveBlock();
               keyDOWN = false;
          //if LEFT is pressed
          if ( e.getKeyCode() == 37 ) {
               keyLEFT = true;
               if ( checkCollision( blockPositionX - 1, blockPositionY ) == false ) {
                    blockPositionX = blockPositionX - 1;
                    this.repaint();
                    moveBlock();
               keyLEFT = false;
          //if RIGHT is pressed
          if ( e.getKeyCode() == 39 ) {
               keyRIGHT = true;
               if ( checkCollision( blockPositionX + 1, blockPositionY ) == false ) {
                    blockPositionX = blockPositionX + 1;
                    this.repaint();
                    moveBlock();
               keyRIGHT = false;
* Create the GUI and show it. For thread safety,
* this method should be invoked from the
* event-dispatching thread.
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("SmallWorld");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Create and set up the content pane.
JComponent newContentPane = new SmallWorld();
newContentPane.setOpaque(true); //content panes must be opaque
frame.setContentPane(newContentPane);
//Display the window.
frame.pack();
     frame.setSize(500,520);
frame.setVisible(true);
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
The world DAT file:
111111111111111111111111111111
100010001010001000101000100011
100010001010001000101000100011
100011101010000000001000000001
100010000010000000001000000001
100110000010000000001000000001
100000000010000000001000000001
111100011110000000001000000001
100000000110001110111000111011
100000000000001110111000111011
100000000000000000001000000001
100010001110000000000000000001
100010001110001110111000111011
100011101100000000000000000011
100010000110001110111000111011
100110000100000000000000000011
100000000110000000001000000001
111100011100000000000000000011
100000000100000000000000000011
100000000010000000000000000001
100000000010000000000000000001
100010000000000000000000000001
100010000000001110111000111011
100011101110000000011000000001
100010000110000000011000000001
100110000110000000001000000001
100000000110001110111000111011
111100011110000000011000000001
100000000110000000011000000001
100000000011111111111111111111

Answer 1

I know this is an old posting, but I just saw another question similiar to this and I still have my old code lying around that incorporates most of the suggestions made in this posting. So I thought I'd post my code here in case anybody wants to copy/paste the code. You will still need to use the DAT file provide above as well as provide icons to represent the floor and wall.
import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
public class SmallWorld extends JPanel implements KeyListener, ActionListener
     //WORLD
     String[][] worldArray = new String[30][30];
     //Block colors
     private static Color redBlock = new Color(255,0,0,255);
     private static Color whiteBlock = new Color(255,255,255,255);
     private static Color blackBlock = new Color(0,0,0,150);
     //World images
//     JLabel wall = new JLabel( new ImageIcon("wall.gif") );
//     JLabel floor = new JLabel( new ImageIcon("floor.gif") );
     ImageIcon wallIcon = new ImageIcon("dukewavered.gif");
     ImageIcon floorIcon = new ImageIcon("copy16.gif");
     //Starting coordinates
     int blockPositionX = 1;
     int blockPositionY = 1;
     //Typing area to capture keyEvent
     JTextField typingArea;
     //Viewable area
     JViewport viewable;
     String type = "";
     JLayeredPane layeredPane;
     JPanel worldBack;
     JPanel panel;
     JPanel player;
     Dimension worldSize = new Dimension(1500, 1500);
     public SmallWorld() {
          super( );
          createWorld();
          layeredPane = new JLayeredPane();
          add(layeredPane);
          layeredPane.setPreferredSize( worldSize );
          worldBack = new JPanel();
          layeredPane.add(worldBack, JLayeredPane.DEFAULT_LAYER);
          worldBack.setLayout( new GridLayout(30, 30) );
          worldBack.setPreferredSize( worldSize );
          worldBack.setBounds(0, 0, worldSize.width, worldSize.height);
          worldBack.setBackground( whiteBlock );
          for (int i = 0; i < 30; i++) {
               for (int j = 0; j < 30; j++) {
                    JPanel square = new JPanel( new BorderLayout() );
                    worldBack.add( square );
                    type = worldArray[i][j];
                    if ( type.equals("1") )
                         square.add( new JLabel(wallIcon) );
                    else
                         square.add( new JLabel(floorIcon) );
          //Draw the player
          player = new JPanel();
          player.setBounds(50, 50, 50, 50);
          player.setBackground( Color.black );
          player.setLocation(50, 50);
          layeredPane.add(player, JLayeredPane.DRAG_LAYER);
          //set where the player starts
//          panel = (JPanel)worldBack.getComponent( 31 );
//          panel.add( player );
          //Create the typing area with keyListener, add to window
          typingArea = new JTextField(20);
          typingArea.addKeyListener(this);
          typingArea.setEditable( false );
          add(typingArea);
     //Get the world from the DAT file and translate it into
     //a 2d array to be used by paintComponent
     public void createWorld() {
          String getData = null;
          int countRow = 0;
          try {
               //Get file
               FileReader fr = new FileReader("world.dat");
               BufferedReader br = new BufferedReader(fr);
               getData = new String();
               //read each line from file, store to 2d array
               while ((getData = br.readLine()) != null) {
                    if(countRow < 30) {
                         for (int i = 0; i < 30; i++) {
                              String temp = "" + getData.charAt(i);
                              worldArray[countRow] = temp;
                    countRow++;
          } catch (IOException e) {
          System.out.println("Uh oh, got an IOException error!");
          e.printStackTrace();
     //Move Block around the world
     public void moveBlock() {
          Point pt = new Point();
          pt.x = blockPositionX * 50;
          pt.y = blockPositionY * 50;
          int x = Math.max(0, pt.x - 250);
          int y = Math.max(0, pt.y - 250);
          Rectangle r = new Rectangle(x, y, 550, 550);
          scrollRectToVisible( r );
     //check for collisions with blocks
     public boolean checkCollision(int row, int col) {
          if ( worldArray[col][row].equals("1") ) {
               return true;
          else {
               return false;
     public void keyTyped(KeyEvent e) {
     public void keyPressed(KeyEvent e) {
          updateView( e );
          e.consume();
     public void keyReleased(KeyEvent e) {
     public void actionPerformed(ActionEvent e) {
     //Update the view of the window based on which button is pressed
     protected void updateView( KeyEvent e ) {
          //if UP
          if ( e.getKeyCode() == 38 ) {
               if ( checkCollision( blockPositionX, blockPositionY - 1 ) == false ) {
                    blockPositionY = blockPositionY - 1;
                    moveBlock();
                    player.setLocation(blockPositionX *50, blockPositionY*50);
          //if DOWN
          if ( e.getKeyCode() == 40 ) {
               if ( checkCollision( blockPositionX, blockPositionY + 1 ) == false ) {
                    blockPositionY = blockPositionY + 1;
                    moveBlock();
                    player.setLocation(blockPositionX *50, blockPositionY*50);
          //if LEFT
          if ( e.getKeyCode() == 37 ) {
               if ( checkCollision( blockPositionX - 1, blockPositionY ) == false ) {
                    blockPositionX = blockPositionX - 1;
                    moveBlock();
                    player.setLocation(blockPositionX *50, blockPositionY*50);
          //if RIGHT
          if ( e.getKeyCode() == 39 ) {
               if ( checkCollision( blockPositionX + 1, blockPositionY ) == false ) {
                    blockPositionX = blockPositionX + 1;
                    moveBlock();
                    player.setLocation(blockPositionX *50, blockPositionY*50);
     private static void createAndShowGUI() {
          JFrame frame = new JFrame("SmallWorld");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          JComponent newContentPane = new SmallWorld();
          newContentPane.setPreferredSize( new Dimension(1500, 1500) );
          JScrollPane scrollPane = new JScrollPane( newContentPane );
          scrollPane.setPreferredSize( new Dimension(568, 568) );
          frame.getContentPane().add( scrollPane );
          frame.pack();
          frame.setLocationRelativeTo( null );
          frame.setResizable( false );
          //frame.setSize(500,520);
          frame.setVisible( true );
     public static void main(String[] args) {
          javax.swing.SwingUtilities.invokeLater( new Runnable() {
               public void run() {
                    createAndShowGUI();