PulseView.java

package pt.chambino.p.pulse.view;

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

public class PulseView extends View {

    public PulseView(Context context) {
        super(context);
        init();
    }

    public PulseView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public PulseView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private double[] pulse;
    private int gridSize = 100;
    private int gridStep = 5;

    private Paint pulsePaint;
    private Paint zeroPaint;
    private Paint gridPaint;

    private void init() {
        setNoPulse();

        setBackgroundColor(Color.DKGRAY);
        pulsePaint = initPulsePaint();
        zeroPaint = initZeroPaint();
        gridPaint = initGridPaint();
    }

    private Paint initPulsePaint() {
        Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);
        p.setColor(Color.RED);
        p.setStrokeWidth(4);
        return p;
    }

    private Paint initZeroPaint() {
        Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);
        p.setColor(Color.LTGRAY);
        p.setStrokeWidth(4);
        return p;
    }

    private Paint initGridPaint() {
        Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);
        p.setColor(Color.LTGRAY);
        p.setStrokeWidth(1);
        return p;
    }

    public double[] getPulse() {
        return pulse;
    }

    public void setPulse(final double[] pulse) {
        this.pulse = pulse;
        invalidate();
    }

    public void setNoPulse() {
        setPulse(new double[0]);
    }

    public int getGridSize() {
        return gridSize;
    }

    public void setGridSize(int gridSize) {
        this.gridSize = gridSize;
        invalidate();
    }

    public int getGridStep() {
        return gridStep;
    }

    public void setGridStep(int gridStep) {
        this.gridStep = gridStep;
        invalidate();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        // vertical grid lines
        for (int i = 0; i < gridSize; i += gridStep) {
            canvas.drawLine(x(i), 0, x(i), getHeight(), gridPaint);
        }

        // vertical and horizontal zero lines
        canvas.drawLine(2, 0, 2, getHeight(), zeroPaint);
        canvas.drawLine(0, y(0), getWidth(), y(0), zeroPaint);

        // pulse signal
        for (int i = 1; i < pulse.length; i++) {
            canvas.drawLine(x(i-1), y(pulse[i-1]), x(i), y(pulse[i]), pulsePaint);
        }
    }

    private float x(int x) {
        return x * getWidth() / (gridSize - 1);
    }

    private float y(double y) {
        return (float)(getHeight() / 2. - y * getHeight() / 3.);
    }

}