package com.synthdreams.GalacticBlast;

import net.rim.device.api.ui.component.Dialog;
import java.io.InputStream;
import java.lang.Class;
import javax.microedition.media.Manager;
import javax.microedition.media.Player;
import net.rim.device.api.system.Alert;

// Sound engine
class SND {
    
    Player _musicPlayer; // Java media player
    
    SND() { }
    
    // Play a midi file for background music
    void playMusic(String passMusic)
    {
        try
        {
            // Set InputStream to a midi file included as resource, as specified by
            // passMusic
            InputStream in = getClass().getResourceAsStream("/" + passMusic);            
            
            // Create a media player with mime type of audio/midi using our inputstream
            _musicPlayer = javax.microedition.media.Manager.createPlayer(in, "audio/midi");
            
            // Ready the data and start playing it.  To loop indefinitely, we set loopcount
            // to -1.
            _musicPlayer.realize();
            _musicPlayer.prefetch();
            _musicPlayer.setLoopCount(-1);
            _musicPlayer.start();

        }
        catch (Exception e)
        {
            Dialog.alert("Error playing music");
        }   
    }
    
    // Stop playing music
    void stopMusic()
    {
        try
        {
            // Tell player to stop playing
            _musicPlayer.stop();
            
        }
        catch (Exception e)
        {
            Dialog.alert("Error stopping music");
        }
        
        // Then release the data and close out the player
        _musicPlayer.deallocate();
        _musicPlayer.close();
    }
    
    // The Playsound method plays a simple combinations of tones to simulate a firing
    // noise.  This was necessary, as due to a bug or limitation of the BlackBerry 8830 
    // (the phone I do my testing on), playing a WAV file stopped the midi player and
    // any other sound effects.  Player doesn't appear to mix properly (if at all).  However,
    // a midi file can be played while using the Alert objects startAudio method which
    // can play a sequence of tones, so this is what we've done for now.
    void playSound()
    {
        // A sequence of frequencies and durations (eg 1400hz for 15ms, 1350hz for 15ms, etc)
        short[] fire = {1400, 15, 1350, 15, 1320, 20, 1300, 20, 1250, 25, 1200, 35};
        
        try
        {
            Alert.startAudio(fire, 100);
            
        }
        catch (Exception e)
        {
            Dialog.alert("Error playing sound effect.");
        }   
        
    }
    
    // Activates the phone's vibration functionality for a specific number of ms
    void vibrate(int passMilli)
    {
        Alert.startVibrate(passMilli);
    }
} 

package com.synthdreams.GalacticBlast;

import net.rim.device.api.system.Bitmap;
import net.rim.device.api.system.Display;
import net.rim.device.api.ui.*;
import java.util.Vector;

// The GFX class is our game's graphics engine with all the drawing routines
class GFX 
{
    int _backPos, _backSpeed; // Background position and speed
    Bitmap _backgroundBM; // The bitmap for the background
    Bitmap _healthBM; // The bitmap for the health meter
    Font _gameFont; // The font used for drawing score and lives
    
    GFX() 
    {
        // First see if we can get the BBCondensed font at size 16 for our game font.
        // If not, we just go with the default, but all Blackberrys should have this font.
        try
        {
            _gameFont = FontFamily.forName("BBCondensed").getFont(FontFamily.SCALABLE_FONT,16);
        }
        catch (Exception e) { }
        
        // Load the health bitmap from health.png
        _healthBM = Bitmap.getBitmapResource("health.png");
    }
    
    // Get current background position
    public int getBackPos() { return _backPos; }
    
    // Method that sets the bitmap for the background and sets the scroll speed
    public void initBackground(String passBackground, int passSpeed)
    {
       _backgroundBM = Bitmap.getBitmapResource(passBackground);
       _backPos = 0;
       _backSpeed = passSpeed;
    }
    
    // Primary function for the graphics engine, draws all the objects, text, health, etc
    public void process(Graphics passGraphics, Vector passObjects, int passScore, int passLives)
    {
        // Draw our background at the correct position
        passGraphics.drawBitmap(0,0, Graphics.getScreenWidth(), Graphics.getScreenHeight(), _backgroundBM, 0, _backPos);
        
        // Move our background.  
        _backPos -= _backSpeed;
        
        //If we're at the beginning of our bitmap, reset to end
        if (_backPos < 0)
        {
           _backPos = _backgroundBM.getHeight() - _backSpeed;
        }
        
        // If we're within screenheight of the end of our bitmap, we need to draw another copy to fill in the blank
        if (_backgroundBM.getHeight() - _backPos < Graphics.getScreenHeight()+_backSpeed)
        {
           passGraphics.drawBitmap(0, _backgroundBM.getHeight() - _backPos - _backSpeed, Graphics.getScreenWidth(), Graphics.getScreenHeight(), _backgroundBM, 0, 0);
        }
        
        // Now draw each of our objects to the screen
        for (int lcv = 0 ; lcv < passObjects.size() ; lcv++)
        {
            passGraphics.drawBitmap(((OBJ) passObjects.elementAt(lcv)).getX(),
                                    ((OBJ) passObjects.elementAt(lcv)).getY(),
                                    ((OBJ) passObjects.elementAt(lcv)).getBitmap().getWidth(),
                                    ((OBJ) passObjects.elementAt(lcv)).getBitmap().getHeight(),
                                    ((OBJ) passObjects.elementAt(lcv)).getBitmap(),
                                    0, 0);
        }
        
        // Draw score
        String zeroPad;
        
        // We want to pad the score with 0s
        zeroPad = "";
        if (passScore < 10000)
          zeroPad += "0";        
        if (passScore < 1000)
          zeroPad += "0";
        if (passScore < 100)
          zeroPad += "0";
        if (passScore < 10)
          zeroPad += "0";
          
        // Draw score and lives in white with the game font
        passGraphics.setColor(0xFFFFFF);
        passGraphics.setFont(_gameFont);
        passGraphics.drawText("Score: " + zeroPad + passScore, Graphics.getScreenWidth()-93, 2);
        passGraphics.drawText("Lives: " + passLives, 7, Graphics.getScreenHeight() - 20);
        
        //Draw health, with width dependent on hero's life
        if (((OBJ) passObjects.elementAt(0)).getLife() > 0)
            passGraphics.drawBitmap(7, 7, _healthBM.getWidth() * ((OBJ) passObjects.elementAt(0)).getLife() / 5, _healthBM.getHeight(), _healthBM, 0, 0);
    }

}

package com.synthdreams.GalacticBlast;

import net.rim.device.api.system.Bitmap;
import net.rim.device.api.ui.Graphics;
import java.util.*;

// OBJ is our root class for all objects, it defines behaviors and properties
// that are the same for all objects, whether its the hero, enemies, or photons
class OBJ 
{
    // Objects can have different states, these are general ones
    public static int STATE_NORMAL = 0;  // Object is alive and functioning normally
    public static int STATE_HIT = 100; // Object just got hit, flash red
    public static int STATE_DYING = 1000; // Object is dying, show an explosion
    
    int _posX, _posY, _velX, _velY;  // All objects have position and velocity
    int _life, _value, _state; // All objects have life, point value, and a current state
    OBJ _parent; // All objects can have a parent (e.g. a photon belongs to the object that shot it)
    String _type; // Type is a string that stores what the object is for easy reference
    Bitmap _bitmap; // Bitmap to be drawn for the object
    
    // Objects are initialized globally with a position
    OBJ(int passX, int passY) 
    {
        _posX = passX;
        _posY = passY;
        _velX = 0;
        _velY = 0;
        _life = 1;
        _value = 0;
        _state = STATE_NORMAL;
        _type = "generic";
        
    }
    
    // Setters and getters
    public int getX() { return _posX; }
    public int getY() { return _posY; }
    public void setX(int passX) { _posX = passX; }
    public void setY(int passY) { _posY = passY; }
    public int getVelX() { return _velX; }
    public int getVelY() { return _velY; }
    public void setVelX(int passX) { _velX = passX; }
    public void setVelY(int passY) { _velY = passY; }
    public int getLife() { return _life; }
    public void setLife(int passLife) { _life = passLife; }
    public int getValue() { return _value; }
    public int getState() { return _state; }
    public void setState(int passState) { _state = passState; }
    public String getType() { return _type; }
    public Bitmap getBitmap() { return _bitmap; }
    public OBJ getParent() { return _parent; }
    
    // Process, think, and damager are all specific to the object, so these are blank
    public void process() { }
    public void think(Vector passObjects) { }
    public void damage() { }
    
    // In our game, firing means shooting a photon and playing the zap tone, this is the same
    // for all objects
    public void fire(Vector passObjects, OBJ passParent, int passVelocity)
    {
        Photon tempPhoton;
        
        // If the photon is going up, start it from the top of the object firing it.
        // If its going down, start it from bottom of object firing it
        if (passVelocity > 0)
            tempPhoton = new Photon(passParent.getX(),passParent.getY()+passParent.getBitmap().getHeight(), 0, passVelocity, passParent);        
        else
            tempPhoton = new Photon(passParent.getX(),passParent.getY(), 0, passVelocity, passParent);    
                
        // set X coordinate of photon to the middle of the object firing it
        tempPhoton.setX(tempPhoton.getX() + passParent.getBitmap().getWidth()/2);
        
        // Add the photon object to our object vector
        passObjects.addElement(tempPhoton);
        
        // Play a zap tone
        GamePlay.snd.playSound();
        
    }
    
    
    // Collision detection routine using an AABB test (Axis Align Bounding Box).  This
    // is a quick and easy test great for games with simple squarish sprites which simply
    // looks to see if the bounding boxes overlap in any way.
    public static void collisionDetect(Vector passObjects)
    {
        OBJ tempObject1, tempObject2; // temporarily points to the two objects being tested
        boolean intersect, check; // flags during testing
        
        // Loop through all objects in our vector
        for (int lcv = 0 ; lcv < passObjects.size() ; lcv++)
        {
            // Set tempObject1 to the current object
            tempObject1 = (OBJ) passObjects.elementAt(lcv);
            
            // Now loop from the current object to the end of the vector
            for(int lcv2 = lcv ; lcv2 < passObjects.size() ; lcv2++)
            {
                // Set tempObject2 to the current object of the nested loop
                tempObject2 = (OBJ) passObjects.elementAt(lcv2);
                
                // See if we need to check for collision (e.g. some objects dont matter if 
                // they collide, enemy with enemy or fire with fire for example)
                
                // Assume we dont need to check
                check = false;
                
                // Hero and enemy would be something to check for
                if (tempObject1.getType() == "hero" && tempObject2.getType().startsWith("enemy"))
                    check = true;
                
                // Hero and enemy fired photons would be something to check for    
                if (tempObject1.getType() == "hero" && tempObject2.getType().startsWith("fire") && tempObject2.getParent().getType().startsWith("enemy"))
                    check = true;
               
                // Enemy and hero fired photons would be something ot check for     
                if (tempObject1.getType().startsWith("enemy") && tempObject2.getType().startsWith("fire") && tempObject2.getParent().getType() == "hero")
                    check = true;
                
                // If our check flag is set to true, and the state of the objects is normal
                // (e.g. an object in a hit or exploded state can't collide with something),
                // then lets check for the actual collision
                if (check && tempObject1.getState() == 0 && tempObject2.getState() == 0)
                {
                    
                    // We assume the two objects collided
                    intersect = true;
                    
                    // Left and Right sides of bounding box check
                    if (!(Math.abs((tempObject1.getX() + tempObject1.getBitmap().getWidth()/2) - (tempObject2.getX() + tempObject2.getBitmap().getWidth()/2)) <= tempObject1.getBitmap().getWidth() / 2 + tempObject2.getBitmap().getWidth() / 2))
                        intersect = false;
    
                    // Top and Bottom sides of bounding box check
                    if (!(Math.abs((tempObject1.getY() + tempObject1.getBitmap().getHeight()/2) - (tempObject2.getY() + tempObject2.getBitmap().getHeight()/2)) <= tempObject1.getBitmap().getHeight() / 2 + tempObject2.getBitmap().getHeight() / 2))
                        intersect = false;
    
                    // If the objects collided, damage each one.
                    if (intersect)
                    {
                        tempObject1.damage();
                        tempObject2.damage();
                    }                    
                }
            }
        }    
    }

    // Clean up objects that have died or are way off screen.
    public static int cleanObjects(Vector passObjects)
    {
        OBJ tempObject; // Temporary points to object we're checking
        boolean delFlag; // Flag if we should get rid of it or not
        int scoreAdd; // Aggregate points to add to user's score
        
        // Start out with no points added
        scoreAdd = 0;
        
        // Loop through all objects in our vector
        for (int lcv = 0 ; lcv < passObjects.size() ; lcv++)
        {
            // Set tempObject to current object
            tempObject = (OBJ) passObjects.elementAt(lcv);
            
            // Assume we're not deleting it
            delFlag = false;
            
            // Check the object's state.  If its been dying for 10 refreshes, its
            // time to get rid of it.
            if (tempObject.getState() > STATE_DYING + 10)
            {
                // In the case of our hero, the player has lives, so if the hero
                // dies, we need to check to see if any lives are left before
                // quitting the game
                if (tempObject.getType() == "hero")
                {
                    // If there are lives left...
                    if (((Hero)tempObject).getLives() > 0)
                    {
                       // Decrement the number of lives left, set state, bitmap,
                       // and position back to normal
                       ((Hero)tempObject).setLives(((Hero)tempObject).getLives()-1);
                       tempObject.setLife(5);
                       tempObject.setState(STATE_NORMAL);
                       tempObject.setX(Graphics.getScreenWidth() / 2);
                       tempObject.setY(Graphics.getScreenHeight() - 50);   
                       tempObject._bitmap = Bitmap.getBitmapResource("herogame.png");
                    }
                    else
                    {
                       // The player is out of lives, lets destroy the hero (which will
                       // end the game)
                       delFlag = true;    
                    }
                }
                else
                {
                    // Enemies only have 1 life, so they are set to be deleted, and we
                    // add their value to the total score the player got this cleanup.
                    delFlag = true;
                    scoreAdd += tempObject.getValue();
                }
            }
            
            // If the object is a photon...
            if (tempObject.getType() == "firephoton" && delFlag == false)
            {  
                // Delete if off left side of screen
                if(tempObject.getX() + tempObject.getBitmap().getWidth() < 0)
                    delFlag = true;
                
                // Delete if off right side of screen    
                if(tempObject.getX() > Graphics.getScreenWidth())
                    delFlag = true;
                    
                // Delete if off top of screen
                if(tempObject.getY() + tempObject.getBitmap().getHeight() < 0)
                    delFlag = true;
                
                // Delete if off bottom of screen    
                if(tempObject.getY() > Graphics.getScreenHeight())
                    delFlag = true;            
            }
            
            // We need to check for enemies that are way off screen.  
            // Normally enemies will swarm around here, but there are 
            // also kamikaze enemies that will aim toward the hero,
            // and if miss, keep going forever
            if (tempObject.getType() == "enemydrone" && delFlag == false)
            {  
                // Check each of the four sides of the screen, if an enemy is
                // past any of them plus 100 pixels its considered lost.  No
                // points are scored for these enemies though.
                if(tempObject.getX() + tempObject.getBitmap().getWidth() < -100)
                    delFlag = true;
                    
                if(tempObject.getX() > Graphics.getScreenWidth() + 100)
                    delFlag = true;
                    
                if(tempObject.getY() + tempObject.getBitmap().getHeight() < -100)
                    delFlag = true;
                    
                if(tempObject.getY() > Graphics.getScreenHeight() + 100)
                    delFlag = true;            
            }
            
            // If the delete flag is true
            if (delFlag)
            {
                // Remove the object from the vector
                passObjects.removeElementAt(lcv);
                
                // Set our temporary object to null
                tempObject = null;
                
                // If this was our hero object (eg location 0), then we return a -1
                // to communicate this back to our processing routine
                if (lcv == 0)
                {
                    return(-1);
                }
            }
        }
        
        // If our hero is still alive, we return to the number of points scored
        return scoreAdd;
    }
        
    // A quick method simply to ensure screen bound objects don't go off screen.
    // For now this is just our hero, but there may be other objects that function
    // like this.    
    public void boundToScreen()
    {
      // If the coordinates are off screen in any direction, correct the coordinate and
      // set that velocity to 0
      if (_posX < 0)
      {
         _posX = 0;
         _velX = 0;
      }
      
      if (_posY < 0)
      {
          _posY = 0;
          _velY = 0;
      }
      
      if (_posX > Graphics.getScreenWidth() - _bitmap.getWidth())
      {
          _posX = Graphics.getScreenWidth() - _bitmap.getWidth();
          _velX = 0;
      }

      if (_posY > Graphics.getScreenHeight() - _bitmap.getHeight())
      {
          _posY = Graphics.getScreenHeight() - _bitmap.getHeight();
          _velY = 0;
      }
        
    }

}

// Hero object
class Hero extends OBJ
{
   int _lives; // The hero (the player) has multiple lives, different from other objects
   
   Hero(int passX, int passY)
   {
      super(passX, passY);
      
      // Set bitmap to herogame
      _bitmap = Bitmap.getBitmapResource("herogame.png");    
      
      // Set coordinates, velocity, lives, and type identifier
      _velX = 0;
      _velY = 0;
      _life = 5;
      _lives = 2;
      _type = "hero";
   }    
   
   // Hero processing
   public void process()
   {
      // The hero has a max velocity of 10 in any direction
      if (_velX > 10)
        _velX = 10;
      
      if (_velX < -10)
        _velX = -10;
      
      if (_velY > 10)
        _velY = 10;
      
      if (_velY < -10)
        _velY = -10;
        
      // Movement is simply adding velocity to position  
      _posX += _velX;
      _posY += _velY;  

      // If the current life of the hero is less than 1, we check the state of hero
      if (_life < 1)
      {
        
        // If the hero is currently in a normal state, it is put into a dying state
        if (_state == STATE_NORMAL)
        {
            // Set hero bitmap to an explosion
            _bitmap = Bitmap.getBitmapResource("explosiongame.png");    
            
            // Set state to dying
            _state = STATE_DYING;
            
            // Vibrate the phone
            GamePlay.snd.vibrate(180);
        }
        
      }
      
      // If the hero is in an abnormal state (hit or dying), there is additional processing
      // that must happen
      if (_state > STATE_NORMAL)
      {
          // First, we increment the state by 1.  Non normal states are temporary and are checked
          // for terminate by seeing if the initial state value plus a certain number of 
          // refreshes has been reached.  It allows the object to be in a abnormal state for 10 
          // refreshes, 3 refreshes, however many necessary, and then continue onto 
          // some other state, either back to normal or deleted.
          _state++;
          
          // If the ship has been in the hit state for more than 3 refreshes, set it back to normal
          if ((_state > STATE_HIT + 3) && (_state < STATE_DYING))
          {
            _state = STATE_NORMAL;
            _bitmap = Bitmap.getBitmapResource("herogame.png");    
          }
      }
            
      // Bound our hero to the screen
      boundToScreen();
   }
   
   // Our hero's damage method
   public void damage()
   {
      // Decrease life (not lives) by 1
      _life--;
      
      // If life is still above 0, change our hero to the hit state
      if (_life > 0)
      {
        _bitmap = Bitmap.getBitmapResource("herogamehit.png");
        _state = STATE_HIT;
      }
   }
   
   // Our hero's fire method for when it fires a photon
   public void fire(Vector passObjects)
   {
      //Call the parents fire method, with a velocity of -20
      super.fire(passObjects, this, -20);
   }
   
   // Lives setter and getter
   public int getLives() { return _lives; }
   public void setLives(int passLives) { _lives = passLives; }
        
}

// Photon class
class Photon extends OBJ
{
    
    // Initializes like hero object, only has photon.png as a bitmap, and starts
    // with a program specified velocity
    Photon(int passX, int passY, int passVelX, int passVelY, OBJ passParent)
    {
      super(passX, passY);
      _bitmap = Bitmap.getBitmapResource("photon.png");    
      _velX = passVelX;
      _velY = passVelY;
      _type = "firephoton";        
      _parent = passParent;
    }

    // Photon processing is simple, we simply move the object in accordance to its
    // velocity
    public void process()
    {
        
      // Position = Position + Velocity
      _posX += _velX;
      _posY += _velY;  
               
    }


    // When a photon is damaged, it simply dies and disappears instantly.  
    // This is accomplished by setting the state to STATE_DYING + 11.  Since
    // we put objects in the dying state for 10 frames before delition, this
    // immediate deletes it.
    public void damage()
    {
      _life = 0;
      _state = STATE_DYING+11;
    }

}

// Our enemy class
class EnemyDrone extends OBJ
{
   int _AIRoutine; // AI routine stores what kind of enemy this is, normal or kamikaze
   
   // Enemy initialization is like other objects, except we randomly choose what
   // kind of AI routine it should use
   EnemyDrone(int passX, int passY)
   {
      super(passX, passY);
      _bitmap = Bitmap.getBitmapResource("enemygame.png");    
      _value = 50;
      _type = "enemydrone";
      
      // Statistically, 3 out of 5 enemies are normal, 2 are kamikaze
      if (GamePlay.rndGenerator.nextInt() % 10 < 6)
         _AIRoutine = 0;
      else
         _AIRoutine = 1;
         
   }    
   
   // Enemy processing is identical to hero processing, except enemies don't
   // have a hit state, since they have one life (not to be confused with lives), 
   // one hit kills them, hence theres no need for a hit state
   public void process()
   {
      _posX += _velX;
      _posY += _velY;  
      
      if (_life < 1)
      {
        if (_state == STATE_NORMAL)
        {
            _bitmap = Bitmap.getBitmapResource("explosiongame.png");    
            _state = STATE_DYING;
            GamePlay.snd.vibrate(180);            
        }
       
        _state++;
      }
      
   }
   
   // The think method is where the individual enemy AI takes place
   public void think(Vector passObjects)
   {
    
      // If they've blown up, they can no longer think
      if (_life < 1)
         return;
      
      // We start off with a velocity of 0 in both directions
      _velX = 0;
      _velY = 0;
      
      // Grab a handle on the hero object so we know how to direct our enemies
      Hero tempHero = (Hero) passObjects.elementAt(0);
      
      // If we're in normal AI mode
      if (_AIRoutine == 0)
      {
        // If hero is to our right, set velocity to right
        if (_posX + _bitmap.getWidth() / 2 < tempHero.getX() + tempHero.getBitmap().getWidth()/2)
            _velX = 5;
                    
        // If hero is to our left, set velocity to our left
        if (_posX + _bitmap.getWidth() / 2 > tempHero.getX() + tempHero.getBitmap().getWidth()/2)
            _velX = -5;
        
        // Enemies try to stay 40 pixels above hero    
        if (_posY + _bitmap.getHeight()  < tempHero.getY() - 40)
            _velY = 5;
                    
        // If enemy is below hero, they move up            
        if (_posY > tempHero.getY() + tempHero.getBitmap().getHeight())
            _velY = -5;
            
        // Add a little bit of random movement in
        _velX += GamePlay.rndGenerator.nextInt() % 4 - 2;
        _velY += GamePlay.rndGenerator.nextInt() % 4 - 2;
        
        // Random firing, fire 1 in 7 times thinking
        if (GamePlay.rndGenerator.nextInt() % 4 == 1)
        {
            fire(passObjects);
        }
     }
     else
     {         
        // Kamikaze AI is the same for as above for horizontal processing.  
        if (_posX + _bitmap.getWidth() / 2 < tempHero.getX() + tempHero.getBitmap().getWidth()/2)
            _velX = 5;
                    
        if (_posX + _bitmap.getWidth() / 2 > tempHero.getX() + tempHero.getBitmap().getWidth()/2)
            _velX = -5;
      
        // For vertical though, the enemy drone is always going downward at a faster rate
        _velY = 8;   
     }
   }

   // If enemy is damaged, their life is decreased
   public void damage()
   {
     _life--;
   }

   // An enemy firing calls the Object's fire method with a downward direction
   public void fire(Vector passObjects)
   {
      super.fire(passObjects, this, 20);
   }

}

package com.synthdreams.GalacticBlast;

import net.rim.device.api.ui.UiApplication;
import net.rim.device.api.ui.container.FullScreen;
import net.rim.device.api.ui.Graphics;
import net.rim.device.api.system.Characters;
import net.rim.device.api.system.Application;
import java.lang.Thread;
import java.lang.Math;
import java.util.*;

// Gameplay extends FullScreen only, it doesn't need the functionality of the
// MainScreen object.  Either are screens though, and can be pushed onto the 
// screen stack
// Special Note: For those familiar with the concept double buffering, supposedly
// the rim UI automatically does this.  It seems to from what I can see, I
// notice no tearing or graphic anomalies.
// For those unfamiliar, if you blit (write) graphic data directly primary graphic
// buffer, it is out of sync with the refresh of the screen.  This can cause
// tearing or other weird graphic issues, as half of the screen is still being shown
// where the objects were, and the other half where the objects are now.  This
// is solved by first drawing to a back buffer, and then flipping the entire
// back buffer with the front during the screen's refresh.  In java there are
// specific game-oriented screen classes to do this, but supposedly the RIM
// libs do this automatically. 
public class GamePlay extends FullScreen
{
    // These three objects are called from many places and are made public
    public static GFX gfx;  // Static object for graphics control
    public static SND snd;  // Static object for sound control
    public static Random rndGenerator; // Static object for random numbers
    
    Refresher _refresher;  // Thread that continually refreshes the game
    EnemyAI _enemyai; // Thread when the enemies think
    Vector _objects; // A vector of all objects currently in play
    
    boolean _active; // Flag if our game is currently active or not (eg did we lose)
    int _score; // Player's current score
    
    // Getters for active and score
    boolean getActive() { return _active; }
    int getScore() {return _score; }
    
    // Refresh is a type of thread that runs to refresh the game.  
    // Its job is to make sure all the processing is called for each object, update the background,
    // update score, check for end of game, etc.  This is the main heartbeat.
    private class Refresher extends Thread
    {
        // When the object is created it starts itself as a thread
        Refresher()
        { 
           start();
        }
        
        // This method defines what this thread does every time it runs.
        public void run()
        {
            // Temporary variable that stores the score value of all
            // the objects that were just cleaned (destroyed/removed)
            // return a negative number if we died
            int cleanReturn;
            
            // This thread runs while the game is active
            while (_active)
            {
                
                // Level population/processing, responsible for creating new enemies
                processLevel();
                
                // Perform physics by calling each object's process command.  Objects
                // are unique and control their own physics (e.g. a photon blast can move
                // faster than our hero ship), so we loop through all our objects
                // and call the process method on each.
                for (int lcv = 0 ; lcv < _objects.size() ; lcv++)
                {
                    ((OBJ) _objects.elementAt(lcv)).process();
                }
                
                // Collision detection of objects.  If they collide, this method
                // will call the damage method of each object, which might lead
                // to no life for the object
                OBJ.collisionDetect(_objects);
                
                // Clean up stuff that's gone (e.g. life of 0 and in 
                // destroyable state, eg explosion graphic), quit if we were destroyed
                cleanReturn = OBJ.cleanObjects(_objects);
                
                // If we didn't die, add the score, redraw, etc.
                if (cleanReturn >= 0)
                {
                   _score += cleanReturn;
                   
                   // Now that all our processing is done, tell the graphics engine to 
                   // redraw the screen through a call to invalidate (invalidates the screen
                   // and automatically causes a redraw)
                   invalidate();
                }
                else
                {
                   // if we died, mark active as false.
                   _active = false;    
                }
                   
                try
                {
                    // Attempt to sleep for 50 ms
                    this.sleep(50);
                        
                }
                catch (InterruptedException e)
                {
                    // Do nothing if we couldn't sleep, we don't care about exactly perfect
                    // timing.
                }
            }
        }
                
    }

    // We have a separate thread that takes care of enemy AI.  This allows us to control how
    // quickly the enemies think outside of our main refresh thread.  That way we can make
    // dumb enemies that think much slower than the action happening around them, or smart
    // enemies that think as fast.
    private class EnemyAI extends Thread
    {
        EnemyAI()
        { 
           start();
           
        }
        
        public void run()
        {
            // Just make sure the thread doesn't accidentally run when the game is over
            while (_active)
            {
                // Loop through all the objects and call the think method, which
                // controls the actions of that object.  Technically, this call's
                // the hero's think method as well, but Hero doesn't have the
                // think method overridden from the parent's, which is just blank,
                // so the hero does no automatic thinking.
                for (int lcv = 0 ; lcv < _objects.size() ; lcv++)
                {
                    if (_active)
                        ((OBJ) _objects.elementAt(lcv)).think(_objects);
                }
                
                try
                {
                    // Enemies think 5 times a second
                    this.sleep(1000/5);
                        
                }
                catch (InterruptedException e)
                {
                    // Do nothing, again we don't care if timing isn't exact
                }
            }

        }
        
    }

    public GamePlay()
    {
        snd = new SND(); // Create sound engine
        gfx = new GFX(); // Create graphics engine
    
        rndGenerator = new Random(); // Create random number generator

        _active = true; // Mark the game as active
        _score = 0; // Start with a score of 0

        // Set our background to stars.png with a speed of 3 pixels per refresh
        gfx.initBackground("stars.jpg", 3);

        // Start our music playing.  Something odd I noticed with my Blackberry 8830,
        // which may either be a bug or some functionality I'm missing from the
        // sound routines, is the volume starts out very quiet the first time you
        // start playing. If you stop the music playing and play it again, the volume
        // is fine.  This might not be true for all Blackberrys, but it doesn't hurt
        // anything to start, stop, and start again, so that's what we've done here,
        // just to solve the volume bug/misundertsanding.
        snd.playMusic("music.mid");
        snd.stopMusic();
        snd.playMusic("music.mid");

        // Create a new vector to hold all the active objects (hero, enemies, photons, etc)
        _objects = new Vector();
        
        // Our hero will always be the very first object in the vector.
        _objects.addElement(new Hero(Graphics.getScreenWidth() / 2, Graphics.getScreenHeight() - 50));
        
        // Create the refresher and enemy AI last, we want to make sure all our objects are setup first
        // so the threads don't make use of uninitialized objects
        _refresher = new Refresher();        
        _enemyai = new EnemyAI();
       
    }
  
    // Process level is responsible for new computer generated events in the game.  In our
    // case, the only one really is creating new enemies.  
    public void processLevel()
    {
        OBJ tempObject;
        
        // Throw a new enemy in every 25 pixels.  This can be made more complex if desired
        // of course
        if (gfx.getBackPos() % 25 == 0)
        {
            // Create a new enemy drone with the X coordinate somewhere between the two edges of the
            // screen
            tempObject = new EnemyDrone(rndGenerator.nextInt() % Graphics.getScreenWidth(), 0);
            
            // Set the Y coordinate to above the screen, so it comes in from the top
            tempObject.setY(tempObject.getY() - tempObject.getBitmap().getHeight() + 3);
            
            // Add the enemy to the object vector
            _objects.addElement(tempObject);    
        }
    }
 
    // This method is called when the invalidate method is called from the refresh thread.
    // We have it passing the graphics object over to our graphics engine so our
    // custom graphics routines can take care of any drawing necessary.
    protected void paint(Graphics graphics)
    { 
       gfx.process(graphics, _objects, _score, ((Hero)_objects.elementAt(0)).getLives()); 
    }
    
    // The keyChar method is called by the event handler when a key is pressed.  
    public boolean keyChar(char key, int status, int time) 
    {
        
        boolean retVal = false;
        
        switch (key)
        {
            // If escape is pressed, we set the game to inactive (quit)
            case Characters.ESCAPE:
                _active = false;
                retVal = true;
                break;
                
            // If the spacebar is pressed, we call the fire method of our
            // hero object, causing him to fire a photon
            case Characters.SPACE:
                ((Hero)_objects.elementAt(0)).fire(_objects);

                retVal = true;
                break;
            
            default:
               break;
        }
                 
        return retVal;
    }
    
    // The navigationMovement method is called by the event handler when the trackball is used. 
    protected boolean navigationMovement(int dx, int dy, int status, int time)
    {
        // If the trackball was scrolled in the horizontal direction, we add that amount to
        // our hero's X velocity
        if (dx != 0)
            ((OBJ)_objects.elementAt(0)).setVelX(dx/Math.abs(dx)*5+((OBJ)_objects.elementAt(0)).getVelX());

        // If the trackball was scrolled in the vertical direction, we add that amount to
        // our hero's Y velocity            
        if (dy != 0)
            ((OBJ)_objects.elementAt(0)).setVelY(dy/Math.abs(dy)*5+((OBJ)_objects.elementAt(0)).getVelY());
            
        return true;
    }
    
}

package com.synthdreams.GalacticBlast;

import net.rim.device.api.ui.UiApplication;

/**
 * Initial main class that starts the ball rolling
 * UiApplication is extended to provide Blackberry
 * functionality, specifically the Event Dispatcher
 * and Screen pusher
 */
public class GalacticBlast extends UiApplication
{
  
    public static void main(String[] args)
    {
        GalacticBlast GalacticBlast = new GalacticBlast();
        
        // The Blackberry's message pump, handles key
        // presses and system events
        GalacticBlast.enterEventDispatcher();
    }
    
    public GalacticBlast()
    {
        // The first thing we do is show the menu screen, defined by the
        // 'Menu' class.  We accomplish this with a call to pushScreen,
        // which puts screens on the stack (Class specified must be a type
        // of screen, such as MainScreen).  The top most screen is the
        // one shown.  Our first one will be the menu, and later the game
        // itself will sit on top of this.  When the game quits, it will
        // pop that screen off the stack and return to the menu screen.
        pushScreen(new Menu());              
    }
} 

package com.synthdreams.GalacticBlast;

import net.rim.device.api.ui.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.ui.container.*;

/**
 * The menu class handles showing the main menu and intercepting when the user quits or 
 * begins the game.  If the user presses the button to begin, the Menu class starts
 * the game going.
 */

class Menu extends MainScreen
{
    GamePlay _game;  // GamePlay handles the action part of the game itself
    int _invokeID; // A handle to our invocation of scanning for when the game ends
    
    // To add functionality to clicking the button, we need to override the button's
    // trackwheelClick method.  Here we define _startButton as a button with
    // text, positioning, and trackwheelClick we want.
    ButtonField _startButton = new ButtonField("Start Game!", ButtonField.FIELD_HCENTER | ButtonField.FIELD_BOTTOM)
    {

       protected boolean trackwheelClick(int status, int time)
       {
          // If the button is pressed, we create a new GamePlay object
          _game = new GamePlay();
          
          // Then we push it onto the screen stack.  This then becomes the
          // active screen.  See GalacticBlast.java for notes about pushing
          // screens onto the stack
          getUiEngine().pushScreen(_game);
          
          // The invokeLater method allows us to continually run a segment of
          // code from outside the GamePlay object.  In this case, we do
          // this to monitor if the gameplay object is active our not.  
          // When the player loses, the object marks itself inactive, at
          // which point we first cancel invoking further, then stop
          // the music from playing, then pop the gameplay screen off
          // the stack so we return to the main menu.
          _invokeID = getApplication().invokeLater(new Runnable()
            {
                public void run()
                {
                    // Check to see if the game is done.
                    if (_game.getActive() == false)
                    {
                        // Cancel invoking this piece of code again (normally is invoked
                        // every 500 ms, as specified below)
                        getApplication().cancelInvokeLater(_invokeID);
                        
                        // Kill the music
                        GamePlay.snd.stopMusic();
                        
                        // Pop the gameplay screen off the stack, which returns
                        // the user to the main menu
                        getUiEngine().popScreen(_game);
                        
                        // Display the final score
                        Dialog.inform("Final Score: " + _game.getScore());
                        
                        // We're done with our game object now
                        _game = null;
                    }
                }
            }
            , 500,true); // rerun this code every 500ms
          
          return true;
       }    
    };   
    
    // Normally LabelFields are arranged in a very plain order depending on the
    // Layout manager.  They'll repeat vertically with the option of left/center/right
    // justifying.  But sometimes it's nice to be able to specificy exactly in X,Y coordinates
    // where you want the field to go.  This class, in conjunction with the Custom Manager
    // defined below, allows for this
    // Additionally, a "customStyle" is defined for the field.  For our cases, this 
    // is either left to 0 for normal X,Y positioning, set to 1 for X set to 1/8th the total
    // width of the screen, or set to 2 for X+fieldwidth set to 7/8th the total width of the screen.
    // 1/8th and 7/8th for the edge of the text allows for columns to be made, for scores,
    // instructions, or anything else.  More custom centering or something more dynamic
    // could be done with this variable, but its fine for our purposes right now.
    class CustomTextField extends LabelField
    {
       int _xPos, _yPos, _customStyle; // coordinates and style
       
       // We pass in the coordinates and the custom style
       CustomTextField(String passLabel, int passStyle, int passX, int passY)
       {
              super(passLabel);
              _xPos = passX;
              _yPos = passY;
              _customStyle = passStyle;
       }    
       
       // Getters for position and style
       int getX() { return _xPos; }
       int getY() { return _yPos; }
       int getCustomStyle() { return _customStyle; }
    }
    
    // Our custom manager is where the magic happens for allowing customtextfields
    // to be placed at any X,Y coordinate.  It reads in the coordinates from the
    // field and places it at those coordinates in the layout.  It will also
    // look at custom layout, and if centered is specified, will ignore the X coordinate
    // and center it at the Y coordinate on the screen.  Additionally, the total height
    // of the manager can be control how much space it takes up regardless of how many
    // fields it contains
    class CustomManager extends Manager
    {
        int _managerHeight; // Total height of the manager
        
        // Pass in desired height.  Scrolling is turned off in both directions.
        public CustomManager(int passHeight)
        {
            super(Manager.NO_HORIZONTAL_SCROLL | Manager.NO_VERTICAL_SCROLL);
            _managerHeight = passHeight;
        }   
        
        // Sublayout is called automatically to position all the internal fields to this
        // layout.  Its sublayouts job to read in the custom coordinates of each of the fields
        // and place them accordingly.
        protected void sublayout(int width, int height) 
        {
            CustomTextField field;
        
            // Loop through all the fields contained with the layout manager
            for (int lcv = 0; lcv < getFieldCount(); lcv++)
            {
                //Get the field.
                field = (CustomTextField)getField(lcv);
            
                //Obtain the custom x and y coordinates for
                //the field and set the position for
                //the field.
                switch (field.getCustomStyle())
                {
                   // Custom style 1 is for the left side of the text to be at 1/8th the width
                   // of the screen
                   case 1:
                        setPositionChild(field, width / 8 , field.getY());
                        break;
                        
                   // Custom style 2 is for the right side of the text to be at 7/8ths the width
                   // of the screen    
                   case 2:
                        setPositionChild(field, width * 7 / 8 - field.getPreferredWidth(), field.getY());    
                        break;
                        
                   // Any other custom style gets position strictly from X,Y
                   default:
                        setPositionChild(field, field.getX(), field.getY());  
                    
                }
                 
                
                 //Layout the field.
                 layoutChild(field, width, height);
            }

            //Set the manager's dimensions
            setExtent(width, _managerHeight);
        }
        
        public int getPreferredWidth()
        {
            return Graphics.getScreenWidth();
        }

        public int getPreferredHeight()
        {
            return Graphics.getScreenHeight();
        }
    }

    // Menu constructor
    public Menu()
    {
        // First, turn off scroll bars for this screen in case we accidentally push past the 
        // edge with our fields/whitespace
        super(NO_VERTICAL_SCROLL);

        // We set the title on the screen
        LabelField title = new LabelField("Galactic Blast Demo", LabelField.FIELD_HCENTER);
        setTitle(title);

        // CustomManagers can also be used just as space buffers.  First we make
        // 20 pixels of space
        getScreen().add(new CustomManager(20));
        
        // Add some text        
        add(new LabelField("Instructions", LabelField.FIELD_HCENTER));
        
        // Create another custom manager, but this one we'll use for more than just
        // spacing, we'll actually position some text fields (our instructions)
        CustomManager instManager = new CustomManager(Graphics.getScreenHeight() - 145);                
        getScreen().add(instManager);       

        // A multi-d array that will store our instruction fields
        CustomTextField instArray[][] = new CustomTextField[3][2];
        
        instArray[0][0]= new CustomTextField("Trackball", 1, 0, 20);
        instArray[1][0] = new CustomTextField("Space", 1, 0, 40);
        instArray[2][0] = new CustomTextField("Escape", 1, 0, 60);
        instArray[0][1] = new CustomTextField("Move Ship", 2, 0, 20);
        instArray[1][1] = new CustomTextField("Fire Cannon", 2, 0, 40);
        instArray[2][1] = new CustomTextField("Quit Game", 2, 0, 60);

        // Loop through our array and add each field to the layout manager with a different
        // font
        for (int lcv = 0 ; lcv < 3 * 2 ; lcv++)
        {
            instArray[lcv%3][lcv/3].setFont(Font.getDefault().derive(Font.PLAIN, 16));
            instManager.add(instArray[lcv%3][lcv/3]);
        }

        // add our button that has the click method overridden
        add(_startButton);
        
        // Add a buffer of 10 pixels
        getScreen().add(new CustomManager(10));   
        
        // More text
        LabelField copyrightText = new LabelField("Copyright 2008 Synthetic Dreams", LabelField.FIELD_HCENTER);        
        copyrightText.setFont(Font.getDefault().derive(Font.ITALIC, 14));
        add(copyrightText);
       
    }
        
}