Android Open Source - DeathRally Joystick

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License

The source code is released under:

GNU General Public License

Java Source Code

/*
 * Copyright (c) 2012 Johannes Vestlund <Johannes@westlundarna.se>
 * /*www . j a v  a  2 s .  com*/
 * This file is part of DeathRally
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by 
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even implied warranty of
 * MERCHANTABILITY or FITTNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package project.gamedev.deathrally.game.controls;


import project.gamedev.deathrally.game.MainGamePanel;
import project.gamedev.deathrally.game.model.GameAction;
import project.gamedev.deathrally.game.model.Player;
import project.gamedev.deathrally.game.view.GameRenderer;
import project.gamedev.deathrally.game.view.JoystickView;
import android.opengl.GLU;

public class Joystick {
  private MainGamePanel controller;
  private float centerX;
  private float centerY;
  private int radius = 100;
  private JoystickView vJoystick;
  private Player owner;
  
  /**
   * The constructor
   * @param owner is the player that are using the joystick, typically the user. 
   * @param context is the game-panel responsible for acting controller.
   */
  public Joystick(Player owner, MainGamePanel context){
    this.owner = owner;
    this.controller = context;
  }
  
  public void createUI(float px, float py){
    this.centerX = px;
    this.centerY = py;
    float[] coordsOrigo = new float[16];
    int[] viewport = GameRenderer.getViewport();
    float posY = viewport[3] - py;
    
    /*
     * Remember to change to "new" implementation!
     */
    GLU.gluUnProject(px, posY, 0, GameRenderer.getModelViewMatrix(), 0,
        GameRenderer.getProjectionMatrix(), 0, viewport, 0, coordsOrigo, 0);
    float[] coordsEdge = new float[16];
    GLU.gluUnProject(px+radius, posY, 0, GameRenderer.getModelViewMatrix(), 0, 
        GameRenderer.getProjectionMatrix(), 0, GameRenderer.getViewport(), 0, coordsEdge, 0);
    
    float glRadius = coordsOrigo[0] - coordsEdge[0];
    vJoystick = new JoystickView(coordsOrigo[0], coordsOrigo[1], glRadius);
    controller.addVisualObj(vJoystick);
  }
  
  /**
   * When touch-motion is aborted, the user stops touching the screen, the visual view
   * of the joystick should disappear and the actions should be reset.
   */
  public void reset(){
    /*
    controller.recieveAction();
    controller.recieveAction();
    */
    if(vJoystick != null){
      vJoystick.destroy();
    }
    vJoystick = null;
  }
  
  /**
   * When action is dispatched to joystick this method catches it and sends meaningful
   * GameActions back.
   * 
   * @param px x-position of touched pixel.
   * @param py y-position of touched pixel.
   */
  public void catchAction(float px, float py){
    
    if(inCircle(px,py)){
      float dx = px-centerX;
      float dy = py-centerY;
      
      controller.recieveAction(GameAction.ACCELERATE);
      if (dx <= 0) {
        controller.recieveAction(GameAction.TURN_LEFT);
      } else {
        controller.recieveAction(GameAction.TURN_RIGHT);
      }
      
    }
  }

  /**
   * Calculates if a point is inside joystick area.
   * May benefit from being generalized.
   * 
   * @param px
   * @param py
   * @return true if point is inside joystick area.
   */
  private boolean inCircle(float px, float py) {
    double sq_dist = Math.pow(centerX - px, 2) + 
        Math.pow(centerY - py, 2); 
    return sq_dist <= Math.pow(radius, 2);
  }
}

Java Source Code List

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