ParticleSystem.java

package no.agens.depth.headers;

import android.animation.ArgbEvaluator;
import android.animation.ValueAnimator;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;

import com.github.florent37.depth.lib.MathHelper;

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

public class ParticleSystem extends Renderable {
    public static final int DURATION = 10000;
    Paint particlePaint = new Paint();
    long lastEmit;
    private int emitInterWall;
    private float gravityY;
    private float randomXPlacement;
    private float minYCoord;
    private float randomMovementY;
    int startColor;
    int endColor;
    private int randomMovementChangeInterval=2000;

    public void setParticleSize(int particleSize) {
        this.particleSize = particleSize;
    }

    int particleSize = 20;

    public void setRandomMovementX(float randomMovement) {
        this.randomMovementX = randomMovement;
    }

    float randomMovementX = 10;

    public ParticleSystem(float x, float y, int emitInterWall, float gravityY, float randomXPlacement) {
        super(null, x, y);
        lastEmit = System.currentTimeMillis();
        particlePaint.setColor(Color.RED);
        this.emitInterWall = emitInterWall;
        this.gravityY = gravityY;
        this.randomXPlacement = randomXPlacement;
    }

    public void setColors(int startColor, int endColor) {
        this.startColor = startColor;
        this.endColor = endColor;
        color = ValueAnimator.ofObject(new ArgbEvaluator(), startColor, endColor, Color.TRANSPARENT).setDuration(DURATION);
    }

    List<Particle> paricles = new ArrayList<>();

    @Override
    public void draw(Canvas canvas) {

        for (int i = 0; i < paricles.size(); i++) {
            Particle p = paricles.get(i);
            setParticlePaintColor(p);
            canvas.drawRect(p.x, p.y, p.x + particleSize, p.y + particleSize, particlePaint);
        }
    }

    @Override
    public void update(float deltaTime, float wind) {
        long currentTimeMillis = System.currentTimeMillis();
        if (lastEmit + emitInterWall < currentTimeMillis) {
            addParticle();
        }
        for (int i = 0; i < paricles.size(); i++) {
            Particle particle = paricles.get(i);
            particle.y += gravityY * deltaTime;
            particle.y += particle.randomSpeedY * deltaTime;
            particle.x += particle.randomSpeedX * deltaTime;
            particle.x += wind * deltaTime;

            if (particle.lastRandomizeChange + randomMovementChangeInterval < currentTimeMillis) {
                particle.lastRandomizeChange = System.currentTimeMillis();
                particle.setRandomSpeed(MathHelper.randomRange(-randomMovementX,randomMovementX), MathHelper.randomRange(-randomMovementY,randomMovementY));
            }
            if (particle.y < minYCoord) {
                paricles.remove(i);
                i--;
            }
        }
    }

    private void addParticle() {
        paricles.add(new Particle(x + MathHelper.randomRange(-randomXPlacement,randomXPlacement), y, MathHelper.randomRange(-randomMovementX,randomMovementX), MathHelper.randomRange(-randomMovementY, randomMovementY)));
        lastEmit = System.currentTimeMillis();
    }



    public void setMinYCoord(float minYCoord) {
        this.minYCoord = minYCoord;
    }

    public void setRandomMovementY(float randomMovementY) {
        this.randomMovementY = randomMovementY;
    }

    ValueAnimator color;

    public void setParticlePaintColor(Particle particle) {
        float currentY = y - particle.y;
        float maxMoveDistance = y - minYCoord;
        float travelDistanceInPercentOfMax = currentY / maxMoveDistance;
        color.setCurrentPlayTime((long) (DURATION * travelDistanceInPercentOfMax));
        particlePaint.setColor((Integer) color.getAnimatedValue());
    }

    public void setRandomMovementChangeInterval(int randomMovementChangeInterval) {
        this.randomMovementChangeInterval = randomMovementChangeInterval;
    }
}