www.pudn.com > resources.zip > JumpCanvas.java
package net.frog_parrot.jump;
import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;
/**
* This class is the display of the game.
*
* @author Carol Hamer
*/
public class JumpCanvas extends javax.microedition.lcdui.game.GameCanvas {
//---------------------------------------------------------
// dimension fields
// (constant after initialization)
/**
* the height of the green region below the ground.
*/
static int GROUND_HEIGHT = 32;
/**
* a screen dimension.
*/
static int CORNER_X;
/**
* a screen dimension.
*/
static int CORNER_Y;
/**
* a screen dimension.
*/
static int DISP_WIDTH;
/**
* a screen dimension.
*/
static int DISP_HEIGHT;
/**
* a font dimension.
*/
static int FONT_HEIGHT;
/**
* the default font.
*/
static Font FONT;
/**
* a font dimension.
*/
static int SCORE_WIDTH;
/**
* The width of the string that displays the time,
* saved for placement of time display.
*/
static int TIME_WIDTH;
//---------------------------------------------------------
// game object fields
/**
* a handle to the display.
*/
Display myDisplay;
/**
* a handle to the MIDlet object (to keep track of buttons).
*/
Jump myJump;
/**
* the LayerManager that handles the game graphics.
*/
JumpManager myManager;
/**
* whether or not the game has ended.
*/
static boolean myGameOver;
/**
* the player's score.
*/
int myScore = 0;
/**
* How many ticks we start with.
*/
int myInitialGameTicks = 950;
/**
* this is saved to determine if the time string needs
* to be recomputed.
*/
int myOldGameTicks = myInitialGameTicks;
/**
* the number of game ticks that have passed.
*/
int myGameTicks = myOldGameTicks;
/**
* whether or not this has been painted once.
*/
boolean myInitialized;
/**
* we save the time string to avoid recreating it
* unnecessarily.
*/
static String myInitialString = "1:00";
/**
* we save the time string to avoid recreating it
* unnecessarily.
*/
String myTimeString = myInitialString;
//-----------------------------------------------------
// gets/sets
/**
* This is called when the game ends.
*/
static void setGameOver() {
myGameOver = true;
GameThread.requestStop();
}
/**
* Find out if the game has ended.
*/
static boolean getGameOver() {
return(myGameOver);
}
//-----------------------------------------------------
// initialization and game state changes
/**
* Constructor sets the data, performs dimension calculations,
* and creates the graphical objects.
*/
public JumpCanvas(Jump midlet) {
super(false);
myDisplay = Display.getDisplay(midlet);
myJump = midlet;
}
/**
* This is called as soon as the application begins.
*/
void start() {
myGameOver = false;
myDisplay.setCurrent(this);
repaint();
}
/**
* sets all variables back to their initial positions.
*/
void reset() {
myManager.reset();
myScore = 0;
myGameOver = false;
myGameTicks = myInitialGameTicks;
myOldGameTicks = myInitialGameTicks;
repaint();
}
/**
* clears the key states.
*/
void flushKeys() {
getKeyStates();
}
//-------------------------------------------------------
// graphics methods
/**
* paint the game graphic on the screen.
*/
public void paint(Graphics g) {
// perform the calculations if necessary:
if(!myInitialized) {
CORNER_X = g.getClipX();
CORNER_Y = g.getClipY();
DISP_WIDTH = g.getClipWidth();
DISP_HEIGHT = g.getClipHeight();
FONT = g.getFont();
FONT_HEIGHT = FONT.getHeight();
SCORE_WIDTH = FONT.stringWidth("Score: 000");
TIME_WIDTH = FONT.stringWidth("Time: " + myInitialString);
myInitialized = true;
}
// clear the screen:
g.setColor(0xffffff);
g.fillRect(CORNER_X, CORNER_Y, DISP_WIDTH, DISP_HEIGHT);
g.setColor(0x0000ff00);
g.fillRect(CORNER_X, CORNER_Y + DISP_HEIGHT - GROUND_HEIGHT,
DISP_WIDTH, DISP_HEIGHT);
// create (if necessary) then paint the layer manager:
try {
if(myManager == null) {
myManager = new JumpManager(CORNER_X, CORNER_Y + FONT_HEIGHT*2,
DISP_WIDTH, DISP_HEIGHT - FONT_HEIGHT*2 - GROUND_HEIGHT);
}
myManager.paint(g);
} catch(Exception e) {
errorMsg(g, e);
}
// draw the time and score
g.setColor(0);
g.setFont(FONT);
g.drawString("Score: " + myScore,
(DISP_WIDTH - SCORE_WIDTH)/2,
DISP_HEIGHT + 5 - GROUND_HEIGHT, g.TOP|g.LEFT);
g.drawString("Time: " + formatTime(),
(DISP_WIDTH - TIME_WIDTH)/2,
CORNER_Y + FONT_HEIGHT, g.TOP|g.LEFT);
// write game over if the game is over
if(myGameOver) {
myJump.setNewCommand();
// clear the top region:
g.setColor(0xffffff);
g.fillRect(CORNER_X, CORNER_Y, DISP_WIDTH, FONT_HEIGHT*2 + 1);
int goWidth = FONT.stringWidth("Game Over");
g.setColor(0);
g.setFont(FONT);
g.drawString("Game Over", (DISP_WIDTH - goWidth)/2,
CORNER_Y + FONT_HEIGHT, g.TOP|g.LEFT);
}
}
/**
* a simple utility to make the number of ticks look like a time...
*/
public String formatTime() {
if((myGameTicks / 16) + 1 != myOldGameTicks) {
myTimeString = "";
myOldGameTicks = (myGameTicks / 16) + 1;
int smallPart = myOldGameTicks % 60;
int bigPart = myOldGameTicks / 60;
myTimeString += bigPart + ":";
if(smallPart / 10 < 1) {
myTimeString += "0";
}
myTimeString += smallPart;
}
return(myTimeString);
}
//-------------------------------------------------------
// game movements
/**
* Tell the layer manager to advance the layers and then
* update the display.
*/
void advance() {
myGameTicks--;
myScore += myManager.advance(myGameTicks);
if(myGameTicks == 0) {
setGameOver();
}
// paint the display
try {
paint(getGraphics());
flushGraphics();
} catch(Exception e) {
errorMsg(e);
}
// we do a very short pause to allow the other thread
// to update the information about which keys are pressed:
synchronized(this) {
try {
wait(1);
} catch(Exception e) {}
}
}
/**
* Respond to keystrokes.
*/
public void checkKeys() {
if(! myGameOver) {
int keyState = getKeyStates();
if((keyState & LEFT_PRESSED) != 0) {
myManager.setLeft(true);
}
if((keyState & RIGHT_PRESSED) != 0) {
myManager.setLeft(false);
}
if((keyState & UP_PRESSED) != 0) {
myManager.jump();
}
}
}
//-------------------------------------------------------
// error methods
/**
* Converts an exception to a message and displays
* the message..
*/
void errorMsg(Exception e) {
errorMsg(getGraphics(), e);
flushGraphics();
}
/**
* Converts an exception to a message and displays
* the message..
*/
void errorMsg(Graphics g, Exception e) {
if(e.getMessage() == null) {
errorMsg(g, e.getClass().getName());
} else {
errorMsg(g, e.getClass().getName() + ":" + e.getMessage());
}
}
/**
* Displays an error message if something goes wrong.
*/
void errorMsg(Graphics g, String msg) {
// clear the screen
g.setColor(0xffffff);
g.fillRect(CORNER_X, CORNER_Y, DISP_WIDTH, DISP_HEIGHT);
int msgWidth = FONT.stringWidth(msg);
// write the message in red
g.setColor(0x00ff0000);
g.setFont(FONT);
g.drawString(msg, (DISP_WIDTH - msgWidth)/2,
(DISP_HEIGHT - FONT_HEIGHT)/2, g.TOP|g.LEFT);
myGameOver = true;
}
}