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About Byron Kiourtzoglou

Byron Kiourtzoglou
Byron is a master software engineer working in the IT and Telecom domains. He is an applications developer in a wide variety of applications/services. He is currently acting as the team leader and technical architect for a proprietary service creation and integration platform for both the IT and Telecom industries in addition to a in-house big data real-time analytics solution. He is always fascinated by SOA, middleware services and mobile development. Byron is co-founder and Executive Editor at Java Code Geeks.

Particle Explosion example

In this tutorial we are going to see how can we create a Particle Explosion effect in our Android Application. An explosion is just a number of particles (pixels or small shapes in this occasion…) that move in random positions and with random speeds around the screen originated from the same source.

In our tutorial we will assume that our particles will be small rectangles and that they will be originated from the same place in the screen. What we have to do then, is just give them horizontal an vertical velocity.
 
 
 
 
To be more accurate you will :

  • create a Particle class that will at least contain the horizontal and vertical velocity, the lifetime , the size and the color of the particle
  • create an update function that will calculate the position and the status (dead or alive…) of the particle at any given moment
  • use the canvas draw() function to draw the calculated position of the particle
  • create an Explosion class that will contain an array of particles that will participate in the explosion
as you can see in the code snippets bellow :
package net.obviam.particles.model;

import android.graphics.Canvas;
import android.graphics.Rect;
import android.util.Log;

public class Explosion {

	private static final String TAG = Explosion.class.getSimpleName();

	public static final int STATE_ALIVE 	= 0;	// at least 1 particle is alive
	public static final int STATE_DEAD 		= 1;	// all particles are dead

	private Particle[] particles;			// particles in the explosion
	private int x, y;						// the explosion's origin
	private float gravity;					// the gravity of the explosion (+ upward, - down)
	private float wind;						// speed of wind on horizontal
	private int size;						// number of particles
	private int state;						// whether it's still active or not

	public Explosion(int particleNr, int x, int y) {
		Log.d(TAG, "Explosion created at " + x + "," + y);
		this.state = STATE_ALIVE;
		this.particles = new Particle[particleNr];
	 	for (int i = 0; i < this.particles.length; i++) {
			Particle p = new Particle(x, y);
			this.particles[i] = p;
		}
	 	this.size = particleNr;
	}

	public Particle[] getParticles() {
		return particles;
	}
	public void setParticles(Particle[] particles) {
		this.particles = particles;
	}
	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 float getGravity() {
		return gravity;
	}
	public void setGravity(float gravity) {
		this.gravity = gravity;
	}
	public float getWind() {
		return wind;
	}
	public void setWind(float wind) {
		this.wind = wind;
	}
	public int getSize() {
		return size;
	}
	public void setSize(int size) {
		this.size = size;
	}

	public int getState() {
		return state;
	}

	public void setState(int state) {
		this.state = state;
	}

	// helper methods -------------------------
	public boolean isAlive() {
		return this.state == STATE_ALIVE;
	}
	public boolean isDead() {
		return this.state == STATE_DEAD;
	}

	public void update() {
		if (this.state != STATE_DEAD) {
			boolean isDead = true;
			for (int i = 0; i < this.particles.length; i++) {
				if (this.particles[i].isAlive()) {
					this.particles[i].update();
					isDead = false;
				}
			}
			if (isDead)
				this.state = STATE_DEAD; 
		}
	}

	public void update(Rect container) {
		if (this.state != STATE_DEAD) {
			boolean isDead = true;
			for (int i = 0; i < this.particles.length; i++) {
				if (this.particles[i].isAlive()) {
					this.particles[i].update(container);
//					this.particles[i].update();
					isDead = false;
				}
			}
			if (isDead)
				this.state = STATE_DEAD; 
		}
	}

	public void draw(Canvas canvas) {
		for(int i = 0; i < this.particles.length; i++) {
			if (this.particles[i].isAlive()) {
				this.particles[i].draw(canvas);
			}
		}
	}
}
package net.obviam.particles.model;

import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;

public class Particle {

	public static final int STATE_ALIVE = 0;	// particle is alive
	public static final int STATE_DEAD = 1;		// particle is dead

	public static final int DEFAULT_LIFETIME 	= 200;	// play with this
	public static final int MAX_DIMENSION		= 5;	// the maximum width or height
	public static final int MAX_SPEED			= 10;	// maximum speed (per update)

	private int state;			// particle is alive or dead
	private float widht;		// width of the particle
	private float height;		// height of the particle
	private float x, y;			// horizontal and vertical position
	private double xv, yv;		// vertical and horizontal velocity
	private int age;			// current age of the particle
	private int lifetime;		// particle dies when it reaches this value
	private int color;			// the color of the particle
	private Paint paint;		// internal use to avoid instantiation

	public int getState() {
		return state;
	}

	public void setState(int state) {
		this.state = state;
	}

	public float getWidht() {
		return widht;
	}

	public void setWidht(float widht) {
		this.widht = widht;
	}

	public float getHeight() {
		return height;
	}

	public void setHeight(float height) {
		this.height = height;
	}

	public float getX() {
		return x;
	}

	public void setX(float x) {
		this.x = x;
	}

	public float getY() {
		return y;
	}

	public void setY(float y) {
		this.y = y;
	}

	public double getXv() {
		return xv;
	}

	public void setXv(double xv) {
		this.xv = xv;
	}

	public double getYv() {
		return yv;
	}

	public void setYv(double yv) {
		this.yv = yv;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public int getLifetime() {
		return lifetime;
	}

	public void setLifetime(int lifetime) {
		this.lifetime = lifetime;
	}

	public int getColor() {
		return color;
	}

	public void setColor(int color) {
		this.color = color;
	}

	// helper methods -------------------------
	public boolean isAlive() {
		return this.state == STATE_ALIVE;
	}
	public boolean isDead() {
		return this.state == STATE_DEAD;
	}

	public Particle(int x, int y) {
		this.x = x;
		this.y = y;
		this.state = Particle.STATE_ALIVE;
		this.widht = rndInt(1, MAX_DIMENSION);
		this.height = this.widht;
//		this.height = rnd(1, MAX_DIMENSION);
		this.lifetime = DEFAULT_LIFETIME;
		this.age = 0;
		this.xv = (rndDbl(0, MAX_SPEED * 2) - MAX_SPEED);
		this.yv = (rndDbl(0, MAX_SPEED * 2) - MAX_SPEED);
		// smoothing out the diagonal speed
		if (xv * xv + yv * yv > MAX_SPEED * MAX_SPEED) {
			xv *= 0.7;
			yv *= 0.7;
		}
		this.color = Color.argb(255, rndInt(0, 255), rndInt(0, 255), rndInt(0, 255));
		this.paint = new Paint(this.color);
	}

	/**
	 * Resets the particle
	 * @param x
	 * @param y
	 */
	public void reset(float x, float y) {
		this.state = Particle.STATE_ALIVE;
		this.x = x;
		this.y = y;
		this.age = 0;
	}

	// Return an integer that ranges from min inclusive to max inclusive.
	static int rndInt(int min, int max) {
		return (int) (min + Math.random() * (max - min + 1));
	}

	static double rndDbl(double min, double max) {
		return min + (max - min) * Math.random();
	}

	public void update() {
		if (this.state != STATE_DEAD) {
			this.x += this.xv;
			this.y += this.yv;

			// extract alpha
			int a = this.color >>> 24;
			a -= 2;								// fade by 5
			if (a <= 0) {						// if reached transparency kill the particle
				this.state = STATE_DEAD;
			} else {
				this.color = (this.color & 0x00ffffff) + (a << 24);		// set the new alpha
				this.paint.setAlpha(a);
				this.age++;						// increase the age of the particle
//				this.widht *= 1.05;
//				this.height *= 1.05;
			}
			if (this.age >= this.lifetime) {	// reached the end if its life
				this.state = STATE_DEAD;
			}

			// http://lab.polygonal.de/2007/05/10/bitwise-gems-fast-integer-math/
			//32bit
//			var color:uint = 0xff336699;
//			var a:uint = color >>> 24;
//			var r:uint = color >>> 16 & 0xFF;
//			var g:uint = color >>>  8 & 0xFF;
//			var b:uint = color & 0xFF;

		}
	}

	public void update(Rect container) {
		// update with collision
		if (this.isAlive()) {
			if (this.x <= container.left || this.x >= container.right - this.widht) {
				this.xv *= -1;
			}
			// Bottom is 480 and top is 0 !!!
			if (this.y <= container.top || this.y >= container.bottom - this.height) {
				this.yv *= -1;
			}
		}
		update();
	}

	public void draw(Canvas canvas) {
//		paint.setARGB(255, 128, 255, 50);
		paint.setColor(this.color);
		canvas.drawRect(this.x, this.y, this.x + this.widht, this.y + this.height, paint);
//		canvas.drawCircle(x, y, widht, paint);
	}

}

 
This was an example of how can you simulate a Particle Explosion in Android.

Related Article:

Reference: Particle Explosion with Android from our JCG partner Tamas Jano at the “Against The Grain” blog.

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