CSE 340, Ex 1. Doodle - Snake

SnakeDoodle.java

/*
 * RESOURCES:
 * http://www.curious-creature.com/2013/12/21/android-recipe-4-path-tracing/
 * (Implementation came from this SO link, however I derived something similar w/ ViewAnimator first)
 * https://stackoverflow.com/questions/50674847/how-to-draw-several-lines-slowly-in-constant-velocity-on-canvas-by-android
 * https://stackoverflow.com/questions/15010156/android-using-paint-to-draw-dashed-line-with-two-different-colors
 */


// Runner class omitted

// We need to create our own Path.
// Why? Well, in order to create a tracing effect,
// the ObjectAnimator needs to modify the phase parameter of the DashPathEffect.
// In the chaos of being intelligent, no Android developer added a setPhase() method to it.
// Alas, we need to simulate this method in an effective wrapper around Path.
class SnakePath extends View {

    Path snakePath;
    Path foodDotsBasePath; // Duplicate base of snakePath
    Path altSnakePath;     // Effect of "Eating" pellets
    Path snakeOutlinePath; // Outline of snake path to follow
    Paint snakePaint;
    Paint foodPaint;
    Paint altSnakePaint;
    Paint snakeOutlinePaint;
    float length;

    public SnakePath(Context context) {
        super(context);
    }

    public void init() {
        snakePath = new Path();

        snakePath.moveTo(0, 600);
        snakePath.lineTo(100, 600);
        snakePath.lineTo(100, 2000);
        snakePath.lineTo(1000, 2000);
        snakePath.lineTo(1000, 1800);
        snakePath.lineTo(300, 1800);
        snakePath.lineTo(300, 1000);
        snakePath.lineTo(500, 1000);
        snakePath.lineTo(500, 1600);
        snakePath.lineTo(1200, 1600);
        snakePath.lineTo(1200, 2000);
        snakePath.lineTo(1300, 2000);
        snakePath.lineTo(1300, 1400);
        snakePath.lineTo(700, 1400);
        snakePath.lineTo(700, 800);
        snakePath.lineTo(300, 800);
        snakePath.lineTo(300, 600);
        snakePath.lineTo(900, 600);
        snakePath.lineTo(900, 1200);
        snakePath.lineTo(1100, 1200);
        snakePath.lineTo(1100, 600);
        snakePath.lineTo(PHONE_DIMS.x, 600);


        // Configure paint of snake
        snakePaint = new Paint();
        snakePaint.setStrokeWidth(18);
        snakePaint.setColor(Color.BLUE);
        snakePaint.setStyle(Paint.Style.STROKE);


        // Now, we'll use the DashPathEffect to *setup* a trace effect
        PathMeasure snakeLength = new PathMeasure(snakePath, false);
        length = snakeLength.getLength();

        // Finally, build the animator.
        ObjectAnimator animator1 = ObjectAnimator.ofFloat(this, "phase", length, 0.0f);
        animator1.setInterpolator(new LinearInterpolator());
        animator1.setDuration(13000);
        animator1.setRepeatCount(ObjectAnimator.INFINITE);
        animator1.setRepeatMode(ObjectAnimator.RESTART);


        // Here's another path that is layered under the snake, to simulate eating the pellets.
        // (offsetting wouldn't work)
        altSnakePath = new Path(snakePath);
        altSnakePaint = new Paint();
        altSnakePaint.setStrokeWidth(40f);
        altSnakePaint.setColor(Color.parseColor("#FAFAFA"));
        altSnakePaint.setStyle(Paint.Style.STROKE);


        // In addition, here is another path to outline the path the snake will take.
        // This helps the dots look more... aligned.
        snakeOutlinePath = new Path(snakePath);
        snakeOutlinePaint = new Paint();
        snakeOutlinePaint.setStrokeWidth(4);
        snakeOutlinePaint.setStyle(Paint.Style.STROKE);


        // Now, as the snake eats things, we can use the PathDashPathEffect to stamp these
        // along the snake's travel path, with no extra positioning required!
        // (I can't figure out how to add multiple pathEffects :c )

        // Copy the base path as duplicate
        foodDotsBasePath = new Path(snakePath);

        // These are the actual dots -- foodDotsPath acts as a base
        Path foodDotsPath = new Path();
        foodDotsPath.addCircle(0f, 0f, 20f, Path.Direction.CW);

        // Apply the stamped dash effect
        PathDashPathEffect dotEffect = new PathDashPathEffect(foodDotsPath, length / 14, 2000f, PathDashPathEffect.Style.TRANSLATE);

        // Configure food paint
        foodPaint = new Paint();
        foodPaint.setPathEffect(dotEffect);
        foodPaint.setStyle(Paint.Style.STROKE);
        foodPaint.setColor(Color.RED);

        // Start the animator as now both snakePath and foodDotsPath (which it controls)
        // have been instantiated.
        animator1.start();

    }


    public void setPhase(float phase) {

        // Since we don't have a real setPhase() method in the PathEffect (grr), we'll
        // have to simulate it by re-instantiating a new PaintEffect with each new phase
        // we want to assign.

        int lengthDiv = 2;
        snakePaint.setPathEffect(new DashPathEffect(new float[] {length / lengthDiv, length / lengthDiv}, phase));
        altSnakePaint.setPathEffect(new DashPathEffect(new float[] {length / lengthDiv, length / lengthDiv}, phase));

        // Now, we force onDraw() to call, redrawing the path!
        invalidate();
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        // The order of the below paths matters!
        canvas.drawPath(foodDotsBasePath, foodPaint);
        canvas.drawPath(altSnakePath, altSnakePaint);

        // This line draws the background path for debugging.
//        canvas.drawPath(snakeOutlinePath, snakeOutlinePaint);

        canvas.drawPath(snakePath, snakePaint);

    }


}