TrafficSim/app/src/main/java/de/hems/trafficsim/TimeRecordView.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;

import java.util.List;

public class TimeRecordView extends View {
    protected Paint paint;
    protected List<VehicleTimeRecord> records;
    protected int pixelPerVehicle;
    protected float trackLength;

    public TimeRecordView(Context context, List<VehicleTimeRecord> records, float trackLength) {
        super(context);
        this.records = records;
        this.trackLength = trackLength;
        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;
        perc = 1 - perc;
        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 onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, 20);
        setMeasuredDimension(widthMeasureSpec, 20);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        this.pixelPerVehicle = (int) (this.getWidth() / this.trackLength);
        int i = 0;
        for (VehicleTimeRecord r : this.records) {
            int left = (int) (this.pixelPerVehicle * r.getPosition());
            this.paint.setColor(getColor(r.getVelocity(), r.getMaxVelocity()));
            canvas.drawRect(left, 0, left + this.pixelPerVehicle - 1,
                    20, this.paint);
            i++;
        }
    }
}