TrafficSim/app/src/main/java/de/hems/trafficsim/TrackView.java

package de.hems.trafficsim;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
import android.view.ViewGroup;

public class TrackView extends View {
    protected Paint paint;
    protected Track track;
    protected int pixelPerVehicle;

    public TrackView(Context context, Track track) {
        super(context);
        this.track = track;
        this.paint = new Paint();
        paint.setColor(Color.BLACK);
        paint.setStyle(Paint.Style.FILL_AND_STROKE);
    }

    protected int getColor(float curVelocity, float maxVelocity) {
        float perc = curVelocity / maxVelocity;
        if (perc <= 0.5) {
            int red = ((int) (2*perc*0xFF)) << 16;
            int green = ((int)0xFF) << 8;
            int blue = 0;
            return 0xff000000 | red | green | blue;
        } else {
            int red = ((int)(0xFF)) << 16;
            int green = ((int)(0xFF-0xFF*(perc-0.5)*2)) << 8;
            int blue = 0;
            return 0xff000000 | red | green | blue;
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        this.pixelPerVehicle = (int) (this.getWidth() / this.track.getTrackLength());
        //super.onDraw(canvas);
        int i = 0;
        for (Vehicle v : this.track.getVehicles()) {
            int left = (int) (this.pixelPerVehicle * v.getPosition());
            this.paint.setColor(getColor(v.getCurVelocity(), v.getMaxVelocity()));
            canvas.drawRect(left, 0, left + this.pixelPerVehicle - 1,
                    20, this.paint);
            i++;
        }
    }
}