I am working on a text-based videogame and created a GUI for it, however, I am having issues getting my two classes to work together. I have a text field in my GUI class that receives input from the user, which I want to send to my Player class so that it can compare it and execute the appropriate methods. I am still very new to programming, so I hope that some of you out there might be able to help me. Excuse the horrendous code.
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
public class GUI extends Player {
String input;
JLabel message;
public GUI() {
JFrame frame = new JFrame("SPACE GAME");
ImageIcon image = new ImageIcon("rocket.png");
frame.setIconImage(image.getImage());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(1200, 800);
frame.setLocationRelativeTo(null);
frame.setFocusable(true);
frame.getContentPane();
JPanel panel = new JPanel();
JTextField commandLine = new JTextField(30);
JLabel message = new JLabel();
frame.add(panel);
panel.setBackground(Color.black);
panel.setLayout(null);
panel.setBorder(BorderFactory.createEmptyBorder(1000, 1000 ,1000 ,1000));
commandLine.setBackground(Color.WHITE);
commandLine.setBounds(5, 730, 300, 30);
commandLine.setBorder(BorderFactory.createLineBorder(Color.GRAY, 3));
commandLine.setFont(new Font("Zig", Font.PLAIN, 18));
commandLine.setForeground(Color.GREEN);
commandLine.setBackground(Color.BLACK);
commandLine.setCaretColor(Color.GREEN);
commandLine.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
String input = commandLine.getText();
}
});
commandLine.setVisible(false);
message.setForeground(Color.GREEN);
message.setText("Welcome to SPACE GAME! Press any key to start.");
message.setBounds(5,665, 1000, 100);
message.setFont(new Font("Courier", Font.PLAIN, 18));
panel.add(message);
panel.add(commandLine);
frame.setVisible(true);
frame.addKeyListener(new KeyListener() {
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyPressed(KeyEvent e) {
int keyCode = e.getKeyCode();
commandLine.setVisible(true);
commandLine.requestFocusInWindow();
message.setText("Type \"help\" for help");
}
#Override
public void keyReleased(KeyEvent e) {
}
});
}
public JLabel getMessage(JLabel message) {
return message;
}
}
import javax.swing.*;
import java.util.Scanner;
public class Player {
//Attributes
private Room currentRoom;
Player player;
JLabel message;
// Handles player movement and commands
public void move() {
player = new Player();
Map map = new Map();
GUI gui = new GUI();
player.currentRoom = map.room1;
Scanner input = new Scanner(System.in);
System.out.println("You are in " + player.currentRoom.getName() + ". " + player.currentRoom.getRoomDescription());
System.out.println("Type \"help\" to get help");
//Commands
boolean isGameRunning = true;
while (isGameRunning) {
String goMessage = input.nextLine();
goMessage = goMessage.toLowerCase();
switch (goMessage) {
case "go north", "north", "go n", "n": goNorth(); break;
case "go east", "east", "go e", "e": goEast(); break;
case "go south", "south", "go s", "s": goSouth(); break;
case "go west", "west", "go w", "w": goWest(); break;
case "exit": isGameRunning = false; break;
case "look":
System.out.println(player.currentRoom.getRoomDescription());
break;
case "help":
System.out.println("""
"go (north, south, east, west)" to choose a direction to go.
"look" gives you a description of the room.
"exit" stops the game.""");
break;
default:
System.out.println("Unknown command");
break;
}
}
}
public void goNorth() {
if (player.currentRoom.getNorthRoom() != null) {
player.currentRoom = player.currentRoom.getNorthRoom();
System.out.println("You are in " + player.currentRoom.getName() + ". " + player.currentRoom.getRoomDescription());
} else {
System.out.println("You cannot go that way");
}
}
public void goEast() {
if (player.currentRoom.getEastRoom() != null) {
player.currentRoom = player.currentRoom.getEastRoom();
System.out.println("You are in " + player.currentRoom.getName() + ". " + player.currentRoom.getRoomDescription());
} else {
System.out.println("You cannot go that way");
}
}
public void goSouth() {
if (player.currentRoom.getSouthRoom() != null) {
player.currentRoom = player.currentRoom.getSouthRoom();
System.out.println("You are in " + player.currentRoom.getName() + ". " + player.currentRoom.getRoomDescription());
} else {
System.out.println("You cannot go that way");
}
}
public void goWest() {
if (player.currentRoom.getWestRoom() != null) {
player.currentRoom = player.currentRoom.getWestRoom();
System.out.println("You are in " + player.currentRoom.getName() + ". " + player.currentRoom.getRoomDescription());
} else {
System.out.println("You cannot go that way");
}
}
}
There are some good things in your code as well as several major issues that may hamper your ability to mash a GUI with your current console-program code, and these include:
You do have some separation of the your program logic into separate classes such as Player, Map, and Room classes, and that is a very good thing, but you still could do more separation of the logic, and doing so can simplify your code making it easier to debug and enhance.
The Player class contains a Player instance, I'm not sure why. The outer main class should probably be re-named from Player to the Game class, and the Player class should be a totally separate class, one that holds the state of a single player instance, and shouldn't create instances of itself as you're doing. The key is to strive to "oop-ify" your code, especially the "model" portion of the code, the code that holds the non-user interface program logic, to make it more object-oriented, since this will make it much easier to allow you to connect a GUI or any other interface, to your model.
Your model (again, named Player) has user interface (UI) code within it: it has Scanner input code within it and println statements. This is problematic, especially now since you want to enhance the program and make it work with a GUI. The key thing that you must do, first and foremost, is to separate the user interface code (agian the code that gets input from the user and that displays output to the user) outside of model class, which is, again, class that holds the program logic.
Your Player class has a lot of non-Player code cluttering it. A basic OOPs principle is that a class should have a single responsibility (called the "single responsibility rule"), and so your Player class should only have code that is needed to encapsulate Player state (such as name, Room, perhaps other properties such as strength, weapons, health, intelligence....) and Player behavior (methods that allow Player to interact with other classes), and nothihg more or less.
Going on the same vein, it appears that all the program data and behaviors seem to be hard-wired into this single main Player class that drives the program. This is very limiting and will hinder your ability to create a rich playing environment with many rooms, items in the rooms, and things like this. Divide and conquer -- get that information out of the main program and put it into OOP-compliant classes, including a Room class that has fields for items it might contain, that has knowledge of its own connections to other rooms.
Your GUI program extends the Player object. This is a major problem since this program structure does not pass the basic test of inheritance, the "is-a" test: logically is a GUI a more specific type of player (much like a Dog is a more specific type of Animal, a structure which passes the "is-a" test)? No, it is not, and while this distinction may seem pendantic, you may try to use Player fields within the GUI class because of this inheritance, but if you try to do this, the code will not work correctly. Remove this inheritance, and instead try to connect classes through "composition" where one class holds an instance of another, rather than extends another. So for instance, the GUI could possibly hold a Player variable rather than extend from Player.
Bottom line:
You will want to fully "OOP-ify" your code before trying to add a GUI
In order for the program to be able to well-meshed with a GUI, I would suggest making your underlying logical code (the non-user interface logic code) much more object-oriented with classes that all have a single responsibility, classes that are easily testable in isolation (away from GUI or any user interface). Start with first principles and the program will be much easier to build.
So, for example, classes that could be considered for an adventure game include:
A Direction class, or better a Direction enum.
This would encapsulate the idea of "direction" and would be used for objects in the game to know which direction they are going and to be able to communicate this to other objects using constants, rather than Strings. The user of an enum would allow the compiler to check that directions are being used correctly, since if you used Strings, say, "West", the compiler would not automatically know if you mis-typed the String and used "Best" instead.
Something simple like this, for example:
public enum Direction {
NORTH, EAST, SOUTH, WEST
}
A GameRoom class
This would hold information telling it its location in the grid of rooms, Strings for both name and description properties, and a game player field or a List of game players if more than one are allowed, perhaps something that contains code like this:....
public class GameRoom {
// map with connections to other game rooms
private Map<Direction, GameRoom> connections = new HashMap<Direction, GameRoom>();
// location information
private int x;
private int y;
// identifying information
private String roomName;
private String description;
// holds any player objects that may be in the room
private List<GamePlayer> playersInRoom = new ArrayList<>();
The class will have appropriate constructors as well as getter and setter methods and also:
An addPlayer(...) method that allows the game to add a player into the room:
public void addPlayer(GamePlayer gamePlayer) {
playersInRoom.add(gamePlayer);
gamePlayer.setCurrentRoom(this); // we'll get to this later
}
A public boolean move(...) method that moves a player contained by the room to a connecting room. It first checks that the room actually contains the player being moved, and then next checks if the room has a connection to another room in the requested direction. If either are false, then the method returns false to let the calling code that the attempted move failed. Otherwise, if the move is allowed, it returns true:
public boolean move(GamePlayer gamePlayer, Direction direction) {
// if the room doesn't currently hold this player
if (!playersInRoom.contains(gamePlayer)) {
return false; // invalid move request
}
// if the room doesn't have a connecting room in the requested direction
if (!connections.containsKey(direction)) {
return false; // invalid move request
}
// otherwise, we're good
playersInRoom.remove(gamePlayer);
connections.get(direction).addPlayer(gamePlayer);
return true;
}
A GamePlayer class
This class will hold several properties such as a String for name and a GameRoom field for the current room, constructors, getter and setter methods. It's declaration and fields could look something like:
public class GamePlayer {
private String name;
private GameRoom currentRoom;
//.... other properties
It too should have a move method that calls the currentRoom GameRoom's move method and returns the same boolean, a result that tells the calling code if the move was valid and successful:
public boolean move(Direction direction) {
return currentRoom.move(this, direction);
}
A GameModel class:
This will hold the state of the current game, fields for players, a data structure to hold all the rooms. It can have its own move method.....
Only after creating your OOP-compliant classes should you move to the next step: the creation of your GUI or "view" class/classes. This class could hold a GameModel instance, and would be responsible for 1) displaying the state of the game (a visual representation of the rooms and the items that they hold), and 2) getting input from the user, and passing that input to the game model for processing.
I like to use an M-V-C program structure, which stands for "Model-View-Controller" where the program logic and GUI are kept as separate as possible, and there may be a controller class or classes that help tie the model and view together. Another principle that I try to follow is to keep the GUI as "dumb" as possible. By dumb, I mean that it should get input from the user, perhaps do the most basic of input verifications, and should display the state of the model, but that's it. Almost all the "brains" of the program should be held by the model itself and not the view.
Proof-of-concept Example:
An incomplete but running "proof-of-concept" example of what I am describing above is shown below. You should copy the program whole, paste it into your IDE into a single file named VideoGame.java, and then should be able to run it. It uses some concepts that you may not yet be familiar with, including the use of Key Bindings to get user input from the GUI and the use of PropertyChangeListeners and PropertyChangeSupport objects to allow clean communication between objects (to notify listeners if the state of one of the model object has changed). This program should respond to pressing of the arrow keys:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.swing.*;
import javax.swing.event.SwingPropertyChangeSupport;
public class VideoGame {
private static final int[][] ROOM_GRID_KEY = {
{ 1, 0, 0, 2, 0, 0, 3, 4 },
{ 5, 6, 7, 8, 9, 10, 11, 0 },
{ 0, 12, 0, 13, 0, 0, 0, 0 },
{ 0, 14, 0, 0, 0, 0, 15, 16 },
{ 17, 18, 0, 19, 0, 0, 20, 0 },
{ 21, 22, 23, 24, 25, 26, 27, 28 }
};
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
GameModel gameModel = new GameModel(ROOM_GRID_KEY);
GameView gameView = new GameView();
new GameController(gameModel, gameView);
JFrame frame = new JFrame("Video Game");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(gameView);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
});
}
}
class GameController {
private GameModel gameModel;
private GameView gameView;
public GameController(GameModel gameModel, GameView gameView) {
this.gameModel = gameModel;
this.gameView = gameView;
ModelListener modelListener = new ModelListener();
gameView.setModel(gameModel);
gameModel.addPropertyChangeListener(modelListener);
}
private class ModelListener implements PropertyChangeListener {
#Override
public void propertyChange(PropertyChangeEvent evt) {
gameView.modelChange(evt);
}
}
}
#SuppressWarnings("serial")
class DisplayPanel extends JPanel {
private JPanel[][] panelGrid;
private int gridCellSize;
private GameModel gameModel;
private GameRoom[][] roomGrid;
public DisplayPanel(int gridCellSize) {
this.gridCellSize = gridCellSize;
}
public void setModel(GameModel gameModel) {
this.gameModel = gameModel;
this.roomGrid = gameModel.getRoomGrid();
int rows = roomGrid.length;
int cols = roomGrid[0].length;
setBackground(Color.BLACK);
setLayout(new GridLayout(rows, cols, 1, 1));
setBorder(BorderFactory.createLineBorder(Color.BLACK));
panelGrid = new JPanel[rows][cols];
for (int r = 0; r < panelGrid.length; r++) {
for (int c = 0; c < panelGrid[r].length; c++) {
JPanel panel = new JPanel(new GridBagLayout());
panelGrid[r][c] = panel;
panel.setPreferredSize(new Dimension(gridCellSize, gridCellSize));
if (roomGrid[r][c] == null) {
panel.setBackground(Color.BLACK);
} else {
panel.setBackground(Color.PINK);
if (roomGrid[r][c].getPlayersInRoom().size() > 0) {
GamePlayer gamePlayer = roomGrid[r][c].getPlayersInRoom().get(0);
String name = gamePlayer.getName();
JLabel label = new JLabel(name);
panel.add(label);
}
}
add(panel);
}
}
// key bindings code
addBindings(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), Direction.SOUTH);
addBindings(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), Direction.NORTH);
addBindings(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), Direction.WEST);
addBindings(KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0), Direction.EAST);
}
private void addBindings(KeyStroke keyStroke, Direction direction) {
int condition = WHEN_IN_FOCUSED_WINDOW;
InputMap inputMap = getInputMap(condition);
ActionMap actionMap = getActionMap();
Action action = new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
gameModel.move(direction);
}
};
inputMap.put(keyStroke, keyStroke.toString());
actionMap.put(keyStroke.toString(), action);
}
public void modelChange(PropertyChangeEvent evt) {
for (int r = 0; r < panelGrid.length; r++) {
for (int c = 0; c < panelGrid[r].length; c++) {
JPanel panel = panelGrid[r][c];
if (roomGrid[r][c] != null) {
if (roomGrid[r][c].getPlayersInRoom().size() > 0) {
GamePlayer gamePlayer = roomGrid[r][c].getPlayersInRoom().get(0);
String name = gamePlayer.getName();
JLabel label = new JLabel(name);
panel.add(label);
} else {
panel.removeAll();
}
}
}
}
revalidate();
repaint();
}
public GameModel getGameModel() {
return gameModel;
}
}
class GameView extends JPanel {
private static final int CELL_SIZE = 80;
private DisplayPanel displayPanel = new DisplayPanel(CELL_SIZE);
private GameModel gameModel;
// private JTextField textField = new JTextField();
public GameView() {
setLayout(new BorderLayout());
add(displayPanel);
// add(textField, BorderLayout.PAGE_END);
}
public void setModel(GameModel gameModel) {
this.gameModel = gameModel;
displayPanel.setModel(gameModel);
}
public void modelChange(PropertyChangeEvent evt) {
displayPanel.modelChange(evt);
}
public GameModel getGameModel() {
return gameModel;
}
}
class GameModel {
public static final String GAME_MODEL = "game model";
private SwingPropertyChangeSupport pcSupport = new SwingPropertyChangeSupport(this);
private GameRoom[][] roomGrid;
private GamePlayer player = new GamePlayer("Fred");
public GameModel(int[][] roomGridKey) {
roomGrid = new GameRoom[roomGridKey.length][roomGridKey[0].length];
// fill room grid with rooms if 1 in grid key array, with null if 0
for (int y = 0; y < roomGridKey.length; y++) {
for (int x = 0; x < roomGridKey[0].length; x++) {
roomGrid[y][x] = roomGridKey[y][x] != 0 ? new GameRoom("Some Room", "Some Description", x, y) : null;
}
}
// make room connections:
for (int y = 0; y < roomGrid.length; y++) {
for (int x = 0; x < roomGrid[0].length; x++) {
GameRoom thisRoom = roomGrid[y][x];
// if no room present, don't
if (thisRoom == null) {
continue;
}
if (x > 0) {
GameRoom otherGameRoom = roomGrid[y][x - 1];
if (otherGameRoom != null) {
thisRoom.putConnection(Direction.WEST, otherGameRoom);
}
}
if (x < roomGrid[0].length - 1) {
GameRoom otherGameRoom = roomGrid[y][x + 1];
if (otherGameRoom != null) {
thisRoom.putConnection(Direction.EAST, otherGameRoom);
}
}
if (y > 0) {
GameRoom otherGameRoom = roomGrid[y - 1][x];
if (otherGameRoom != null) {
thisRoom.putConnection(Direction.NORTH, otherGameRoom);
}
}
if (y < roomGrid.length - 1) {
GameRoom otherGameRoom = roomGrid[y + 1][x];
if (otherGameRoom != null) {
thisRoom.putConnection(Direction.SOUTH, otherGameRoom);
}
}
}
}
// put player in top left room
GameRoom currentRoom = roomGrid[0][0];
if (currentRoom == null) {
// some big error occurred
System.err.println("Current room at 0, 0 is null. Exiting");
System.exit(-1);
}
player.setCurrentRoom(currentRoom);
currentRoom.addPlayer(player);
player.addPropertyChangeListener(pce -> pcSupport.firePropertyChange(GAME_MODEL, null, player));
}
public boolean move(Direction direction) {
boolean success = player.move(direction);
return success;
}
public GamePlayer getPlayer() {
return player;
}
public GameRoom[][] getRoomGrid() {
return roomGrid;
}
public void addPropertyChangeListener(PropertyChangeListener listener) {
pcSupport.addPropertyChangeListener(GAME_MODEL, listener);
}
}
class GamePlayer {
public static final String GAME_PLAYER = "game player";
private SwingPropertyChangeSupport pcSupport = new SwingPropertyChangeSupport(this);
private String name;
private GameRoom currentRoom;
public GamePlayer(String name) {
super();
this.name = name;
}
public String getName() {
return name;
}
public boolean move(Direction direction) {
boolean success = currentRoom.move(this, direction);
return success;
}
public void setCurrentRoom(GameRoom currentRoom) {
GameRoom oldValue = this.currentRoom;
GameRoom newValue = currentRoom;
this.currentRoom = currentRoom;
pcSupport.firePropertyChange(GAME_PLAYER, oldValue, newValue);
}
public GameRoom getCurrentRoom() {
return currentRoom;
}
#Override
public String toString() {
return "GamePlayer [name=" + name + ", currentRoom=" + currentRoom + "]";
}
public void addPropertyChangeListener(PropertyChangeListener listener) {
pcSupport.addPropertyChangeListener(GAME_PLAYER, listener);
}
}
class GameRoom {
// map with connections to other game rooms
private Map<Direction, GameRoom> connections = new HashMap<Direction, GameRoom>();
// location information
private int x;
private int y;
// identifying information
private String roomName;
private String description;
// holds any player objects that may be in the room
private List<GamePlayer> playersInRoom = new ArrayList<>();
public GameRoom(String roomName, String description, int x, int y) {
this.roomName = roomName;
this.description = description;
this.x = x;
this.y = y;
}
public boolean move(GamePlayer gamePlayer, Direction direction) {
// if the room doesn't currently hold this player
if (!playersInRoom.contains(gamePlayer)) {
return false; // invalid move request
}
// if the room doesn't have a connecting room in the requested direction
if (!connections.containsKey(direction)) {
return false; // invalid move request
}
// otherwise, we're good
playersInRoom.remove(gamePlayer);
connections.get(direction).addPlayer(gamePlayer);
return true;
}
public void addPlayer(GamePlayer gamePlayer) {
playersInRoom.add(gamePlayer);
gamePlayer.setCurrentRoom(this);
}
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
public String getRoomName() {
return roomName;
}
public String getDescription() {
return description;
}
public List<GamePlayer> getPlayersInRoom() {
return playersInRoom;
}
public Map<Direction, GameRoom> getConnections() {
return connections;
}
public void putConnection(Direction direction, GameRoom otherGameRoom) {
connections.put(direction, otherGameRoom);
}
#Override
public String toString() {
return "GameRoom [x=" + x + ", y=" + y + "]";
}
}
enum Direction {
NORTH, EAST, SOUTH, WEST
}
Again, compile and run this code and use the arrow keys to move "Fred" around the grid.
A more complete program would separate the data completely out of the code and allow for file I/O for reading in the room grid into the program, possibly by creating a CSV file or files to hold the room information, or if the data is expected to grow and be more complex, then a relational database such as one that uses one of the flavors of SQL.
Since you've made the GUI extend the player, all you need to do is call the desired function from the ActionListener on the input field.
commandLine.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
String input = commandLine.getText();
if (input == "go north") {
GoNorth();
}
// .....
}
});
However, things are pretty messy. There's no real reason for the GUI to extend the player, for starters. I'd advise you to separate the GUI class from Player. That way, you won't need to use the Scanner or Print, and instead collect all your GUI functionality in the GUI class.
For instance:
public void goNorth() {
if (player.currentRoom.getNorthRoom() != null) {
player.currentRoom = player.currentRoom.getNorthRoom();
gui.print("You are in " + player.currentRoom.getName() + ". " + player.currentRoom.getRoomDescription())
} else {
gui.print("You cannot go that way");
}
}
You would need to implement a print function in the GUI class, that added a line of text to the message box, but I'm sure you were planning on that to begin with.
In the GUI class, you would then have a reference to the player, so reading the input field would look something like this:
commandLine.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
String input = commandLine.getText();
switch(input) {
case "go north":
player.goNorth();
break;
...
}
}
});
Mouse.java
package game.input;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseWheelEvent;
// holds information about mouse events.
// eg, presses of buttons.
public class Mouse extends MouseAdapter {
// the position of the mouse.
public static int x, y;
// Is the mouse pressed.
public static boolean pressed;
// Is the mouse held.
public static boolean held;
// Is the mouse hovered over the window.
public static boolean focused;
// Is the mouse being dragged.
public static boolean dragging;
// no mouse wheel support.
#Override
public void mouseWheelMoved(MouseWheelEvent event) {}
#Override
public void mouseDragged(MouseEvent event) {
x = event.getX();
y = event.getY();
dragging = true;
}
#Override
public void mouseMoved(MouseEvent event) {
x = event.getX();
y = event.getY();
}
#Override
public void mouseEntered(MouseEvent event) {
focused = true;
}
#Override
public void mouseExited(MouseEvent event) {
focused = false;
}
#Override
public void mousePressed(MouseEvent event) {
held = true;
}
#Override
public void mouseReleased(MouseEvent event) {
held = false;
dragging = false;
pressed = true;
}
}
Keyboard.java
package game.input;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
// holds information about key events.
public class Keyboard extends KeyAdapter {
// which keys are being held down.
private static boolean[] heldKeys;
// which keys are being clicked
private static boolean[] clickedKeys;
// size of arrays.
private final int size;
public Keyboard() {
// there are 255 valid key codes.
// plus one for the array size.
size = 256;
clickedKeys = new boolean[size];
heldKeys = new boolean[size];
}
// when the key is pressed.
#Override
public void keyPressed(KeyEvent event) {
// catches out of bounds error.
if(event.getKeyCode() > size)
return;
// key is being held.
heldKeys[event.getKeyCode()] = true;
}
#Override
public void keyReleased(KeyEvent event) {
// catches out of bounds error.
if(event.getKeyCode() > size)
return;
// key is let go.
heldKeys[event.getKeyCode()] = false;
// when key is let go, it gets interpreted as it being pressed.
clickedKeys[event.getKeyCode()] = true;
}
// returns whether or not the key is held.
public static boolean keyHeld(Key key) {
if(heldKeys != null)
return heldKeys[key.keyCode];
return false;
}
// returns whether or not the key is clicked.
public static boolean keyClicked(Key key) {
if(clickedKeys != null)
return clickedKeys[key.keyCode];
return false;
}
// resets key input.
public static void resetKeys() {
if(clickedKeys != null)
for(int i = 0; i < clickedKeys.length; i++)
clickedKeys[i] = false;
}
public enum Key {
// movement keys.
LEFT(37), UP(38), RIGHT(39), DOWN(40),
// x key.
A(88),
// z key.
B(90),
// enter key.
START(10);
private int keyCode;
private Key(int keyCode) {
this.keyCode = keyCode;
}
};
}
Game.java
package game;
import java.awt.Graphics2D;
import game.input.Keyboard;
import game.input.Mouse;
import game.room.Room;
import userInterface.containers.BB_Window;
// creates a new game
public final class Game {
// the window that the game resides in.
private static BB_Window window;
// the current room that is drawn to the window.
private static Room room;
private static GameLoop gameLoop;
// game constructor cannot be called.
private Game() {}
// inits the game.
// ie, adds input to the game (key and mouse).
public static void init(BB_Window window) {
if(gameLoop != null)
return;
// creates mouse and keyboard listeners.
Mouse mouse = new Mouse();
Keyboard keyboard = new Keyboard();
// adds input listeners to the window.
window.getJFrame().addKeyListener(keyboard);
window.getCanvas().addMouseListener(mouse);
window.getCanvas().addMouseMotionListener(mouse);
// init game loop
gameLoop = new GameLoop();
// init window
Game.window = window;
gameLoop.start();
}
// updates the current room and resets input.
protected static void update() {
// if room doesn't exist, don't update it.
if(room == null)
return;
// updates current room.
Game.room.update();
// resets mouse input.
Mouse.pressed = false;
// resets key input.
Keyboard.resetKeys();
// if a mouse or key button is clicked,
// then it would have to be reset to false here.
}
// renders the current room.
protected static void render() {
// if room doesn't exist, don't render it.
if(room == null)
return;
// creates graphics object from the window canvas.
Graphics2D graphics = (Graphics2D) window.getCanvas().getBufferStrategy().getDrawGraphics();
// creates the screen for next drawing.
graphics.clearRect(0, 0, window.getWidth(), window.getHeight());
// renders the current room.
Game.room.render(graphics);
// shows the buffer.
window.getCanvas().getBufferStrategy().show();
// removes graphics object.
graphics.dispose();
}
// sets the current room to a new one.
public static void setRoom(Room newRoom) {
newRoom.init();
Game.room = newRoom;
}
// returns the current room.
public static Room getRoom() {
return Game.room;
}
// returns width of window.
public static int getWindowWidth() {
return window.getWidth();
}
// returns height of window.
public static int getWindowHeight() {
return window.getHeight();
}
// stops the game loop.
public static void stop() {
gameLoop.stop();
}
}
GameLoop.java
package game;
public class GameLoop implements Runnable {
// the thread that the game runs on.
private Thread thread;
// is the game running.
private boolean running;
// starts the game loop.
// inits the thread and calls its start method.
public void start() {
// you can't start the game if it is started.
if(running)
return;
// starts the game.
running = true;
// creates thread.
thread = new Thread(this);
// starts the game.
// ie, calls thread.run();
thread.start();
}
// stops the game loop.
// interrupts the thread and terminates the currently running JVM.
public void stop() {
// you can't end the game if it is ended.
if(!running)
return;
// ends the game.
running = false;
// interrupts the thread.
// ie, ends the thread.
// this will always end the thread,
// because running is set to false.
thread.interrupt();
// ends the program.
System.exit(0);
}
// this is the game loop.
#Override
public void run() {
// holds information about each frames elapsed time.
double start, previous = System.nanoTime() / 1_000_000_000.0;
// time.
double actualFrameTime, realTime = 0;
// should the game be rendered.
boolean render;
// fps
final int FPS = 60;
final double DESIRED_FRAME_TIME = 1.0 / FPS;
// while the game is running
while(running) {
// calculates the elapsed time of the frame.
// converts from nano seconds to seconds
// by dividing by one billion.
start = System.nanoTime() / 1_000_000_000.0;
actualFrameTime = start - previous;
previous = start;
// the game time is updated by the elapsed frame time.
realTime += actualFrameTime;
// resets it to back to false.
render = false;
// if time surpasses desired frame time, game should update.
while(realTime >= DESIRED_FRAME_TIME && realTime != 0) {
realTime -= DESIRED_FRAME_TIME;
Game.update();
// if the game is updated, the game should render.
// if the game is not updated, the game doesn't render.
render = true;
}
if(render)
Game.render();
// sleep if game should not render.
// reduces cpu usage by a lot.
else
try {
// sleep for one millisecond.
Thread.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
BB_Window.java
package userInterface.containers;
import java.awt.Canvas;
import java.awt.Dimension;
import java.awt.image.BufferStrategy;
import javax.swing.JFrame;
// the JFrame that the game will reside in.
public final class BB_Window {
private JFrame window;
private Canvas canvas;
private Dimension windowDimension;
// constructs the canvas, window, and buffer.
public BB_Window(String title, int width, int height) {
// creates dimension.
windowDimension = new Dimension(width, height);
// creates a canvas with a bunch of defaults.
canvas = new Canvas();
// sets a non-changeable size.
canvas.setPreferredSize(windowDimension);
canvas.setMinimumSize(windowDimension);
canvas.setMaximumSize(windowDimension);
// cannot be focused for event listeners.
canvas.setFocusable(false);
// creates window with a bunch of defaults.
window = new JFrame();
window.getContentPane().add(canvas);
window.setTitle(title);
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setResizable(false);
window.pack();
window.setVisible(true);
// center of screen.
window.setLocationRelativeTo(null);
BufferStrategy bufferStrategy = canvas.getBufferStrategy();
if(bufferStrategy == null)
canvas.createBufferStrategy(3);
}
// returns the frame.
public JFrame getJFrame() {
return window;
}
// returns the window width.
public int getWidth() {
return windowDimension.width;
}
// returns the window height.
public int getHeight() {
return windowDimension.height;
}
// returns the canvas.
public Canvas getCanvas() {
return canvas;
}
}
Room.java
package game.room;
import java.awt.Graphics2D;
// future functionality might be added,
// which is why this class is abstract and not interface.
// represents a room/location in your Game
// eg, a town, a house, a forest, and a cave are all examples of rooms.
public abstract class Room {
public abstract void init();
public abstract void update();
public abstract void render(Graphics2D graphics);
}
I feel that these files are the only ones needed to understand how my game library functions.
However, I notice that whenever I test out my game library, there is a very noticeable stutter that occurs every few seconds, and lasts for a few seconds. This is very annoying. However, what is more annoying is that this blocky/laggy movement is more noticeable on my computer than on other computers. What is going on with my computer for this to be occurring? How do I fix this? Here is an example of how my game library works.
Game.setRoom(new Room() {
private int x, y;
#Override
public void init() {
x = 0;
y = 0;
}
#Override
public void update() {
x++;
y++;
}
#Override
public void render(Graphics2D graphics) {
graphics.fillRect(x, y, 100, 100);
}});
Game.init(new BB_Window("Test", 640, 640));
This example program draws a rectangle that moves diagonally down the screen.
However, sometimes, the rectangle seems to "skip" pixels and moves more than it should.
I tried recording my screen to show exactly what is going on, but for some reason the stutter is not showing up in the video.
I tried enabling hardware acceleration by doing
System.setProperty("sun.java2d.opengl", "true");
but that didn't do anything.
My computer isn't bad at all, so why is the game running more smoother on other computers than on mine?
And what can I do to fix this in my game library?
Thank you in advance.
I'm trying to write a game in java3d on Linux and for that I need a proper KeyListener.
Did anyone of you know how to do it? I'm currently using following code, I found somewhere on the net. It's working pretty good, holding down just one key, but as soon, as I press more than one (like space and w) it will do unexpected things...
public class RepeatingReleasedEventsFixer implements AWTEventListener {
private final HashMap<Integer, ReleasedAction> _map = new HashMap<Integer, ReleasedAction>();
public void install() {
Toolkit.getDefaultToolkit().addAWTEventListener(this, AWTEvent.KEY_EVENT_MASK);
}
public void remove() {
Toolkit.getDefaultToolkit().removeAWTEventListener(this);
}
#Override
public void eventDispatched(AWTEvent event) {
assert event instanceof KeyEvent : "Shall only listen to KeyEvents, so no other events shall come here";
assert assertEDT(); // REMEMBER THAT THIS IS SINGLE THREADED, so no need for synch.
// ?: Is this one of our synthetic RELEASED events?
if (event instanceof Reposted) {
// -> Yes, so we shalln't process it again.
return;
}
// ?: KEY_TYPED event? (We're only interested in KEY_PRESSED and KEY_RELEASED).
if (event.getID() == KeyEvent.KEY_TYPED) {
// -> Yes, TYPED, don't process.
return;
}
final KeyEvent keyEvent = (KeyEvent) event;
// ?: Is this already consumed?
// (Note how events are passed on to all AWTEventListeners even though a previous one consumed it)
if (keyEvent.isConsumed()) {
return;
}
// ?: Is this RELEASED? (the problem we're trying to fix!)
if (keyEvent.getID() == KeyEvent.KEY_RELEASED) {
// -> Yes, so stick in wait
/**
* Really just wait until "immediately", as the point is that the subsequent PRESSED shall already have been
* posted on the event queue, and shall thus be the direct next event no matter which events are posted
* afterwards. The code with the ReleasedAction handles if the Timer thread actually fires the action due to
* lags, by cancelling the action itself upon the PRESSED.
*/
final Timer timer = new Timer(2, null);
ReleasedAction action = new ReleasedAction(keyEvent, timer);
timer.addActionListener(action);
timer.start();
_map.put(Integer.valueOf(keyEvent.getKeyCode()), action);
// Consume the original
keyEvent.consume();
}
else if (keyEvent.getID() == KeyEvent.KEY_PRESSED) {
// Remember that this is single threaded (EDT), so we can't have races.
ReleasedAction action = _map.remove(Integer.valueOf(keyEvent.getKeyCode()));
// ?: Do we have a corresponding RELEASED waiting?
if (action != null) {
// -> Yes, so dump it
action.cancel();
}
// System.out.println("PRESSED: [" + keyEvent + "]");
}
else {
throw new AssertionError("All IDs should be covered.");
}
}
/**
* The ActionListener that posts the RELEASED {#link RepostedKeyEvent} if the {#link Timer} times out (and hence the
* repeat-action was over).
*/
private class ReleasedAction implements ActionListener {
private final KeyEvent _originalKeyEvent;
private Timer _timer;
ReleasedAction(KeyEvent originalReleased, Timer timer) {
_timer = timer;
_originalKeyEvent = originalReleased;
}
void cancel() {
assert assertEDT();
_timer.stop();
_timer = null;
_map.remove(Integer.valueOf(_originalKeyEvent.getKeyCode()));
}
#Override
public void actionPerformed(#SuppressWarnings ("unused") ActionEvent e) {
assert assertEDT();
// ?: Are we already cancelled?
// (Judging by Timer and TimerQueue code, we can theoretically be raced to be posted onto EDT by TimerQueue,
// due to some lag, unfair scheduling)
if (_timer == null) {
// -> Yes, so don't post the new RELEASED event.
return;
}
// Stop Timer and clean.
cancel();
// Creating new KeyEvent (we've consumed the original).
KeyEvent newEvent = new RepostedKeyEvent((Component) _originalKeyEvent.getSource(),
_originalKeyEvent.getID(), _originalKeyEvent.getWhen(), _originalKeyEvent.getModifiers(),
_originalKeyEvent.getKeyCode(), _originalKeyEvent.getKeyChar(), _originalKeyEvent.getKeyLocation());
// Posting to EventQueue.
Toolkit.getDefaultToolkit().getSystemEventQueue().postEvent(newEvent);
// System.out.println("Posted synthetic RELEASED [" + newEvent + "].");
}
}
/**
* Marker interface that denotes that the {#link KeyEvent} in question is reposted from some
* {#link AWTEventListener}, including this. It denotes that the event shall not be "hack processed" by this class
* again. (The problem is that it is not possible to state "inject this event from this point in the pipeline" - one
* have to inject it to the event queue directly, thus it will come through this {#link AWTEventListener} too.
*/
public interface Reposted {
// marker
}
/**
* Dead simple extension of {#link KeyEvent} that implements {#link Reposted}.
*/
public static class RepostedKeyEvent extends KeyEvent implements Reposted {
public RepostedKeyEvent(#SuppressWarnings ("hiding") Component source, #SuppressWarnings ("hiding") int id,
long when, int modifiers, int keyCode, char keyChar, int keyLocation) {
super(source, id, when, modifiers, keyCode, keyChar, keyLocation);
}
}
private static boolean assertEDT() {
if (!EventQueue.isDispatchThread()) {
throw new AssertionError("Not EDT, but [" + Thread.currentThread() + "].");
}
return true;
}
}
I can't be the only one who still runs into this - meanwhile 15 y.o. - problem and don't want to use timers...
EDIT: What this code is doing is fix the known problem on any Linux distri, where you add a simple KeyListener, which handles keyDowns, but invokes keyReleased Event repeatedly. To clearify my problem here a simple example
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
public class Test5 extends JFrame{
public Test5() {
addKeyListener(new KeyListener() {
boolean keydown = false;
#Override
public void keyTyped(KeyEvent arg0) {
// TODO Auto-generated method stub
}
#Override
public void keyReleased(KeyEvent arg0) {
keydown = false;
System.out.println("keyup");
}
#Override
public void keyPressed(KeyEvent arg0) {
if (keydown){
System.out.println("key is down");
} else {
System.out.println("key not down");
}
keydown = true;
}
});
setDefaultCloseOperation(EXIT_ON_CLOSE);
setSize(400, 400);
setVisible(true);
//new RepeatingReleasedEventsFixer().install(); // This line will fix it for one key pressed
}
public static void main(String[] args) {
new Test5();
}
}
The output without the line being commented out:
key not down
keyup
key not down
keyup
key not down
keyup
key not down
keyup
key not down
keyup
otherwise:
key not down
key is down
key is down
key is down
key is down
key is down
key is down
key is down
key is down
key is down
keyup
Btw. How come, that it's not beeing fixed by now?
EDIT:
I tried the KeyBindings, as suggested, where it comes to these problems:
public class Test5 extends JFrame{
long timestamp = 0;
public Test5() {
((JComponent)getComponent(0)).getInputMap().put(KeyStroke.getKeyStroke('a'), "a");
((JComponent)getComponent(0)).getActionMap().put("a", new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("time: "+(System.currentTimeMillis()-timestamp));
timestamp = System.currentTimeMillis();
}
});
((JComponent)getComponent(0)).getInputMap().put(KeyStroke.getKeyStroke('s'), "s");
((JComponent)getComponent(0)).getActionMap().put("s", new AbstractAction() {
#Override
public void actionPerformed(ActionEvent arg0) {
System.out.println("s");
}
});
((JComponent)getComponent(0)).getInputMap().put(KeyStroke.getKeyStroke('d'), "d");
((JComponent)getComponent(0)).getActionMap().put("d", new AbstractAction() {
#Override
public void actionPerformed(ActionEvent arg0) {
System.out.println("d");
}
});
setDefaultCloseOperation(EXIT_ON_CLOSE);
setSize(400, 400);
setVisible(true);
new RepeatingReleasedEventsFixer().install(); // This line will fix it for one key pressed
}
/**
* #param args
*/
public static void main(String[] args) {
new Test5();
}
Holding down "a" will give me following output:
time: 4171
time: 501
time: 30
time: 30
time: 30
Where the second time is the actual problem. It takes about 470ms too long.
Holding down "s" and then somewhne pressing "d" will give me that output:
s
s
s
s
d
d
d
d
d
So I can't process two actions as the same time, so I can't use KeyBindings
This is not an answer, it is a long comment with a picture and some explanations.
I used your Test5 (without RepeatingReleasedEventsFixer) to hold down a and measure the time responses. The output is of the form
time: t1
time: t2
time: t3
time: t3
time: t3
...
t1 is meaningless since it depends on the current time and has nothing to do with response time (you also seem to ignore it).
t2 is the time it takes for the OS to realize that you're holding the key for repeated input.
t3 is the "sample time" of the held key, or a discretization of the input.
I'm using Windows where I have the following control panel options:
Repeat delay allows me to set t2 between ~257 (short) and ~1050 (long).
Repeat rate allows me to set t3 between ~407 (slow) and ~37 (fast).
For Linux, you'll have to consult someone / somewhere on how to change these values if you don't already know how to.
As for using multiple keys, see this question and answer and the excellent link within (especially the "Motion With Multiple Keys Pressed" section). It's a short tutorial and analysis of key bindings and key listeners, similar to the one I sent you to on this site.
Key bindings will always be preferred over key listeners unless maybe there is some very low level thing you want to do.
After days of researching and putting stuff together, I ended up writing my own Listener combined with a KeyEventDispatcher, here is the code for someone running into the same problem. It can and should be optimized, but is working for now:
Klass to test if a specific key is pressed:
import java.awt.KeyEventDispatcher;
import java.awt.KeyboardFocusManager;
import java.awt.event.KeyEvent;
import java.util.HashMap;
public class IsKeyPressed {
private static boolean wPressed = false;
private HashMap<Integer, Boolean> keys = new HashMap<Integer, Boolean>();
public IsKeyPressed() {
KeyboardFocusManager.getCurrentKeyboardFocusManager().addKeyEventDispatcher(new KeyEventDispatcher() {
#Override
public boolean dispatchKeyEvent(KeyEvent ke) {
synchronized (IsKeyPressed.class) {
switch (ke.getID()) {
case KeyEvent.KEY_PRESSED:
keys.put(ke.getKeyCode(), true);
break;
case KeyEvent.KEY_RELEASED:
keys.put(ke.getKeyCode(), false);
break;
}
return false;
}
}
});
}
public static boolean isWPressed() {
synchronized (IsKeyPressed.class) {
return wPressed;
}
}
public boolean isPressed(int keyCode){
synchronized (IsKeyPressed.class) {
if (keys == null)
return false;
if (keys.get(keyCode) == null)
return false;
return keys.get(keyCode);
}
}
}
Abstract class, thats beeing used for the actions.
public abstract class KeyActionListener {
protected int keyCode;
public KeyActionListener(int keyCode) {
this.keyCode = keyCode;
}
public void setKeyCode(int keyCode){
this.keyCode = keyCode;
}
public int getKeyCode(){
return this.keyCode;
}
public abstract void onKeyDown();
public abstract void onKeyUp();
public abstract void onKeyHolding();
}
Start listening to the keys and run the actions.
import java.util.ArrayList;
import java.util.HashMap;
public class KeyThread extends Thread{
private int sleep = 3;
ArrayList<KeyActionListener> listener = new ArrayList<KeyActionListener>();
IsKeyPressed isPressed = new IsKeyPressed();
HashMap<KeyActionListener, Boolean> pressed = new HashMap<KeyActionListener, Boolean>();
public KeyThread() {
this.start();
}
public void run() {
while (true){
for (int i = 0; i < listener.size(); i++) {
KeyActionListener curListener = listener.get(i);
if (isPressed.isPressed(curListener.getKeyCode()) && !pressed.get(curListener)){
curListener.onKeyDown();
pressed.put(curListener, true);
} else if(!isPressed.isPressed(curListener.getKeyCode()) && pressed.get(curListener)) {
curListener.onKeyUp();
pressed.put(curListener, false);
}
if(isPressed.isPressed(curListener.getKeyCode())){
curListener.onKeyHolding();
}
try{
Thread.sleep(sleep);
} catch(InterruptedException e){
}
}
}
}
public void addKeyActionListener(KeyActionListener l){
listener.add(l);
pressed.put(l, false);
}
}
It seems like this applet will only draw and update DRAWS when the window is resized or minimized. So the applet will not repaint all the time, but only when manipulating the window.
Am I doing something wrong here?
I am following the gameloop presented here: http://www3.ntu.edu.sg/home/ehchua/programming/java/J8d_Game_Framework.html
The code is here:
package newapplet;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class GameApplet extends JApplet { // main class for the game as a Swing application
// Define constants for the game
static final int CANVAS_WIDTH = 493; // width and height of the game screen
static final int CANVAS_HEIGHT = 411;
static final int UPDATE_RATE = 4; // number of game update per second
static final long UPDATE_PERIOD = 1000000000L / UPDATE_RATE; // nanoseconds
static int DRAWS = 0;
// ......
// Enumeration for the states of the game.
public enum gameState {
INITIALIZED, CONNECTING, PLAYING, DISCONNECTED
}
private gameState state;
// Define instance variables for the game objects
// ......
// ......
// Handle for the custom drawing panel
private GameCanvas canvas;
// Constructor to initialize the UI components and game objects
public GameApplet() {
// Initialize the game objects
gameInit();
// UI components
canvas = new GameCanvas();
canvas.setPreferredSize(new Dimension(CANVAS_WIDTH, CANVAS_HEIGHT));
this.setContentPane(canvas);
// Other UI components such as button, score board, if any.
// ......
this.setVisible(true);
}
// All the game related codes here
// Initialize all the game objects, run only once in the constructor of the main class.
public void gameInit() {
// ......
state = gameState.INITIALIZED;
}
// Shutdown the game, clean up code that runs only once.
public void gameShutdown() {
// ......
state = gameState.DISCONNECTED;
}
// To start and re-start the game.
public void gameStart() {
// Create a new thread
Thread gameThread = new Thread() {
// Override run() to provide the running behavior of this thread.
#Override
public void run() {
gameLoop();
}
};
// Start the thread. start() calls run(), which in turn calls gameLoop().
gameThread.start();
}
// Run the game loop here.
private void gameLoop() {
// Regenerate the game objects for a new game
// ......
//state = State.PLAYING;
// Game loop
long beginTime, timeTaken, timeLeft;
while (true) {
beginTime = System.nanoTime();
if (state == gameState.DISCONNECTED) break; // break the loop to finish the current play
if (state == gameState.PLAYING) {
// Update the state and position of all the game objects,
// detect collisions and provide responses.
gameUpdate();
}
// Refresh the display
repaint();
// Delay timer to provide the necessary delay to meet the target rate
timeTaken = System.nanoTime() - beginTime;
timeLeft = (UPDATE_PERIOD - timeTaken) / 1000000L; // in milliseconds
if (timeLeft < 10) timeLeft = 10; // set a minimum
try {
// Provides the necessary delay and also yields control so that other thread can do work.
Thread.sleep(timeLeft);
} catch (InterruptedException ex) { }
}
}
// Update the state and position of all the game objects,
// detect collisions and provide responses.
public void gameUpdate() {
}
// Refresh the display. Called back via rapaint(), which invoke the paintComponent().
private void gameDraw(Graphics2D g2d) {
switch (state) {
case INITIALIZED:
g2d.setColor (Color.red);
g2d.drawString ("init",20,20);
break;
case PLAYING:
g2d.setColor (Color.red);
g2d.drawString ("play",20,20);
break;
case CONNECTING:
g2d.setColor (Color.red);
g2d.drawString ("connecting",20,20);
break;
case DISCONNECTED:
g2d.setColor (Color.red);
g2d.drawString ("disconnect",20,20);
break;
}
g2d.setColor (Color.GREEN);
g2d.drawString ("Re-paint: " + DRAWS,30,30);
this.DRAWS++;
// ......
}
// Process a key-pressed event. Update the current state.
public void gameKeyPressed(int keyCode) {
switch (keyCode) {
case KeyEvent.VK_UP:
// ......
break;
case KeyEvent.VK_DOWN:
// ......
break;
case KeyEvent.VK_LEFT:
// ......
break;
case KeyEvent.VK_RIGHT:
// ......
break;
}
}
// Process a key-released event.
public void gameKeyReleased(int keyCode) { }
// Process a key-typed event.
public void gameKeyTyped(char keyChar) { }
// Other methods
// ......
// Custom drawing panel, written as an inner class.
class GameCanvas extends JPanel implements KeyListener {
// Constructor
public GameCanvas() {
setFocusable(true); // so that can receive key-events
requestFocus();
addKeyListener(this);
}
// Override paintComponent to do custom drawing.
// Called back by repaint().
#Override
public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D)g;
super.paintComponent(g2d); // paint background
setBackground(Color.BLACK); // may use an image for background
// Draw the game objects
gameDraw(g2d);
}
// KeyEvent handlers
#Override
public void keyPressed(KeyEvent e) {
gameKeyPressed(e.getKeyCode());
}
#Override
public void keyReleased(KeyEvent e) {
gameKeyReleased(e.getKeyCode());
}
#Override
public void keyTyped(KeyEvent e) {
gameKeyTyped(e.getKeyChar());
}
}
// main
public static void main(String[] args) {
// Use the event dispatch thread to build the UI for thread-safety.
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new GameApplet();
}
});
}
}
Glancing at that code quickly I can see that you are calling repaint() outside of the Event Dispatch Thread, which can cause issues like the one you are seeing. javax.swing.SwingUtilties.invokeAndWait(Runnable r) will allow you to put that repaint() call on the EDT.
http://docs.oracle.com/javase/tutorial/uiswing/concurrency/dispatch.html
See this code for a few corrections.
// <applet code='GameApplet' width=400 height=50></applet>
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class GameApplet extends JApplet { // main class for the game as a Swing application
// Define constants for the game
static final int CANVAS_WIDTH = 493; // width and height of the game screen
static final int CANVAS_HEIGHT = 411;
static final int UPDATE_RATE = 4; // number of game update per second
static final long UPDATE_PERIOD = 1000000000L / UPDATE_RATE; // nanoseconds
Timer timer;
static int DRAWS = 0;
// ......
// Enumeration for the states of the game.
public enum gameState {
INITIALIZED, CONNECTING, PLAYING, DISCONNECTED
}
private gameState state;
// Define instance variables for the game objects
// ......
// ......
// Handle for the custom drawing panel
private GameCanvas canvas;
// Constructor to initialize the UI components and game objects
public GameApplet() {
// Initialize the game objects
gameInit();
// UI components
canvas = new GameCanvas();
// set the size of the applet in HTML, not the content pane!
canvas.setPreferredSize(new Dimension(CANVAS_WIDTH, CANVAS_HEIGHT));
this.setContentPane(canvas);
// Other UI components such as button, score board, if any.
// ......
//this.setVisible(true);
}
// All the game related codes here
// Initialize all the game objects, run only once in the constructor of the main class.
public void gameInit() {
// ......
state = gameState.INITIALIZED;
gameStart();
}
// Shutdown the game, clean up code that runs only once.
public void gameShutdown() {
// ......
state = gameState.DISCONNECTED;
}
#Override
public void destroy() {
timer.stop();
}
// To start and re-start the game.
public void gameStart() {
// Create a new thread
//Thread gameThread = new Thread() {
// Override run() to provide the running behavior of this thread.
// #Override
// public void run() {
gameLoop();
// }
//};
// Start the thread. start() calls run(), which in turn calls gameLoop().
//gameThread.start();
}
// Run the game loop here.
private void gameLoop() {
// Regenerate the game objects for a new game
// ......
//state = State.PLAYING;
// Game loop
ActionListener al = new ActionListener() {
long beginTime, timeTaken, timeLeft;
public void actionPerformed(ActionEvent ae) {
beginTime = System.nanoTime();
if (state == gameState.DISCONNECTED) {
//break; // break the loop to finish the current play
System.out.println("do SOMETHING here..");
}
if (state == gameState.PLAYING) {
// Update the state and position of all the game objects,
// detect collisions and provide responses.
gameUpdate();
}
// Refresh the display
repaint();
// Delay timer to provide the necessary delay to meet the target rate
timeTaken = System.nanoTime() - beginTime;
timeLeft = (UPDATE_PERIOD - timeTaken) / 1000000L; // in milliseconds
if (timeLeft < 10) timeLeft = 10; // set a minimum
}
};
timer = new Timer(40,al);
timer.start();
}
// Update the state and position of all the game objects,
// detect collisions and provide responses.
public void gameUpdate() {
}
// Refresh the display. Called back via rapaint(), which invoke the paintComponent().
private void gameDraw(Graphics2D g2d) {
switch (state) {
case INITIALIZED:
g2d.setColor (Color.red);
g2d.drawString ("init",20,20);
break;
case PLAYING:
g2d.setColor (Color.red);
g2d.drawString ("play",20,20);
break;
case CONNECTING:
g2d.setColor (Color.red);
g2d.drawString ("connecting",20,20);
break;
case DISCONNECTED:
g2d.setColor (Color.red);
g2d.drawString ("disconnect",20,20);
break;
}
g2d.setColor (Color.GREEN);
g2d.drawString ("Re-paint: " + DRAWS,30,30);
this.DRAWS++;
// ......
}
// Process a key-pressed event. Update the current state.
public void gameKeyPressed(int keyCode) {
switch (keyCode) {
case KeyEvent.VK_UP:
// ......
break;
case KeyEvent.VK_DOWN:
// ......
break;
case KeyEvent.VK_LEFT:
// ......
break;
case KeyEvent.VK_RIGHT:
// ......
break;
}
}
// Process a key-released event.
public void gameKeyReleased(int keyCode) { }
// Process a key-typed event.
public void gameKeyTyped(char keyChar) { }
// Other methods
// ......
// Custom drawing panel, written as an inner class.
class GameCanvas extends JPanel implements KeyListener {
// Constructor
public GameCanvas() {
setFocusable(true); // so that can receive key-events
requestFocus();
addKeyListener(this);
}
// Override paintComponent to do custom drawing.
// Called back by repaint().
#Override
public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D)g;
super.paintComponent(g2d); // paint background
setBackground(Color.BLACK); // may use an image for background
// Draw the game objects
gameDraw(g2d);
}
// KeyEvent handlers
#Override
public void keyPressed(KeyEvent e) {
gameKeyPressed(e.getKeyCode());
}
#Override
public void keyReleased(KeyEvent e) {
gameKeyReleased(e.getKeyCode());
}
#Override
public void keyTyped(KeyEvent e) {
gameKeyTyped(e.getKeyChar());
}
}
}
Note that the addition of the single line comment at the top of the source means that (once compiled) it can be launched from the command line using..
> appletviewer GameApplet.java