Android example source code file (BallEngine.java)

This example Android source code file (BallEngine.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, animatingline, arraylist, ball, ballengine, balleventcallback, ballregion, balls, content, illegalargumentexception, iterator, list, ui, util, utilities, utils

The BallEngine.java Android example source code

/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.android.divideandconquer;

import android.util.Log;
import android.content.Context;
import android.widget.Toast;

import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;


/**
 * Keeps track of the current state of balls bouncing around within a a set of
 * regions.
 *
 * Note: 'now' is the elapsed time in milliseconds since some consistent point in time.
 * As long as the reference point stays consistent, the engine will be happy, though
 * typically this is {@link android.os.SystemClock#elapsedRealtime()} 
 */
public class BallEngine {

    static public interface BallEventCallBack {

        void onBallHitsBall(Ball ballA, Ball ballB);

        void onBallHitsLine(long when, Ball ball, AnimatingLine animatingLine);
    }

    private final float mMinX;
    private final float mMaxX;
    private final float mMinY;
    private final float mMaxY;

    private float mBallSpeed;
    private float mBallRadius;

    private BallEventCallBack mCallBack;

    /**
     * Holds onto new regions during a split
     */
    private List<BallRegion> mNewRegions = new ArrayList(8);

    private List<BallRegion> mRegions = new ArrayList(8);

    public BallEngine(float minX, float maxX,
            float minY,
            float maxY,
            float ballSpeed,
            float ballRadius) {
        mMinX = minX;
        mMaxX = maxX;
        mMinY = minY;
        mMaxY = maxY;
        mBallSpeed = ballSpeed;
        mBallRadius = ballRadius;
    }

    public void setCallBack(BallEventCallBack mCallBack) {
        this.mCallBack = mCallBack;
    }

    /**
     * Update the notion of 'now' in milliseconds.  This can be usefull
     * when unpausing for instance.
     * @param now Milliseconds since some consistent point in time.
     */
    public void setNow(long now) {
        for (int i = 0; i < mRegions.size(); i++) {
            final BallRegion region = mRegions.get(i);
            region.setNow(now);
        }
    }

    /**
     * Rest the engine back to a single region with a certain number of balls
     * that will be placed randomly and sent in random directions.
     * @param now milliseconds since some consistent point in time.
     * @param numBalls
     */
    public void reset(long now, int numBalls) {
        mRegions.clear();

        ArrayList<Ball> balls = new ArrayList(numBalls);
        for (int i = 0; i < numBalls; i++) {
            Ball ball = new Ball.Builder()
                    .setNow(now)
                    .setPixelsPerSecond(mBallSpeed)
                    .setAngle(Math.random() * 2 * Math.PI)
                    .setX((float) Math.random() * (mMaxX - mMinX) + mMinX)
                    .setY((float) Math.random() * (mMaxY - mMinY) + mMinY)
                    .setRadiusPixels(mBallRadius)
                    .create();
            balls.add(ball);
        }
        BallRegion region = new BallRegion(now, mMinX, mMaxX, mMinY, mMaxY, balls);
        region.setCallBack(mCallBack);

        mRegions.add(region);
    }

    public List<BallRegion> getRegions() {
        return mRegions;
    }

    public float getPercentageFilled() {
        float total = 0f;
        for (int i = 0; i < mRegions.size(); i++) {
            BallRegion region = mRegions.get(i);
            total += region.getArea();
            Log.d("Balls", "total now " + total);
        }
        return 1f - (total / getArea());
    }

    /**
     * @return the area in the region in pixel*pixel
     */
    public float getArea() {
        return (mMaxX - mMinX) * (mMaxY - mMinY);
    }

    /**
     * Can any of the regions within start a line at this point?
     * @param x The x coordinate.
     * @param y The y coordinate
     * @return Whether a region can start a line.
     */
    public boolean canStartLineAt(float x, float y) {
        for (BallRegion region : mRegions) {
            if (region.canStartLineAt(x, y)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Start a horizontal line at a certain point.
     * @throws IllegalArgumentException if there is no region that can start a
     *     line at the point.
     */
    public void startHorizontalLine(long now, float x, float y) {
        for (BallRegion region : mRegions) {
            if (region.canStartLineAt(x, y)) {
                region.startHorizontalLine(now, x, y);
                return;
            }
        }
        throw new IllegalArgumentException("no region can start a new line at "
                + x + ", " + y + ".");
    }

    /**
     * Start a vertical line at a certain point.
     * @throws IllegalArgumentException if there is no region that can start a
     *     line at the point.
     */
    public void startVerticalLine(long now, float x, float y) {
        for (BallRegion region : mRegions) {
            if (region.canStartLineAt(x, y)) {
                region.startVerticalLine(now, x, y);
                return;
            }
        }
        throw new IllegalArgumentException("no region can start a new line at "
                + x + ", " + y + ".");
    }

    /**
     * @param now The latest notion of 'now'
     * @return whether any new regions were added by the update.
     */
    public boolean update(long now) {
        boolean regionChange = false;
        Iterator<BallRegion> it = mRegions.iterator();
        while (it.hasNext()) {
            final BallRegion region = it.next();
            final BallRegion newRegion = region.update(now);

            if (newRegion != null) {
                regionChange = true;
                if (!newRegion.getBalls().isEmpty()) {
                    mNewRegions.add(newRegion);
                }

                // current region may not have any balls left
                if (region.getBalls().isEmpty()) {
                    it.remove();
                }
            } else if (region.consumeDoneShrinking()) {
                regionChange = true;
            }
        }
        mRegions.addAll(mNewRegions);
        mNewRegions.clear();

        return regionChange;
    }
}