Multiple properties on multiple balls.

BouncingBalls.java

package com.natebass.learn2draw;

import android.animation.Animator;
import android.animation.Keyframe;
import android.animation.PropertyValuesHolder;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RadialGradient;
import android.graphics.Shader;
import android.graphics.drawable.Animatable;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.OvalShape;
import android.os.Bundle;
import android.view.View;
import android.view.animation.AccelerateInterpolator;
import android.view.animation.BounceInterpolator;
import android.widget.Button;
import android.widget.LinearLayout;

import java.util.ArrayList;
/**
 * This application demonstrates the seeking capability of Animator. The SeekBar in the
 * UI allows you to set the position of the animation. Pressing the Run button will play from
 * the current position of the animation.
 */
public class MultiPropertyAnimation extends Activity {
    private static final int DURATION = 1500;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.animation_seeking);
        LinearLayout container = (LinearLayout) findViewById(R.id.container);
        final MyAnimationView animView = new MyAnimationView(this);
        container.addView(animView);
        Button starter = (Button) findViewById(R.id.startButton);
        starter.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                animView.startAnimation();
            }
        });
    }
    public class MyAnimationView extends View implements Animator.AnimatorUpdateListener {
        private static final float BALL_SIZE = 100f;
        public final ArrayList<ShapeHolder> balls = new ArrayList<ShapeHolder>();
        Sequencer animation = null;
        Animatable bounceAnim = null;
        ShapeHolder ball = null;
        public MyAnimationView(Context context) {
            super(context);
            addBall(50, 0);
            addBall(150, 0);
            addBall(250, 0);
            addBall(350, 0);
        }
        private void createAnimation() {
            if (bounceAnim == null) {
                ShapeHolder ball;
                ball = balls.get(0);
                PropertyAnimator yBouncer = new PropertyAnimator(DURATION, ball, "y",
                        ball.getY(), getHeight() - BALL_SIZE);
                yBouncer.setInterpolator(new BounceInterpolator());
                yBouncer.addUpdateListener(this);
                ball = balls.get(1);
                PropertyValuesHolder pvhY = new PropertyValuesHolder("y", ball.getY(),
                        getHeight() - BALL_SIZE);
                PropertyValuesHolder pvhAlpha = new PropertyValuesHolder("alpha", 1.0f,
                        0f);
                PropertyAnimator yAlphaBouncer = new PropertyAnimator(DURATION/2, ball, pvhY, pvhAlpha);
                yAlphaBouncer.setInterpolator(new AccelerateInterpolator());
                yAlphaBouncer.setRepeatCount(1);
                yAlphaBouncer.setRepeatMode(Animator.REVERSE);
                ball = balls.get(2);
                PropertyValuesHolder pvhW = new PropertyValuesHolder("width", ball.getWidth(),
                        ball.getWidth() * 2);
                PropertyValuesHolder pvhH = new PropertyValuesHolder("height", ball.getHeight(),
                        ball.getHeight() * 2);
                PropertyValuesHolder pvTX = new PropertyValuesHolder("x", ball.getX(), ball.getX() - BALL_SIZE/2f);
                PropertyValuesHolder pvTY = new PropertyValuesHolder("y", 0f, ball.getY(), ball.getY() - BALL_SIZE/2f);
                PropertyAnimator whxyBouncer = new PropertyAnimator(DURATION/2, ball, pvhW, pvhH,
                        pvTX, pvTY);
                whxyBouncer.setRepeatCount(1);
                whxyBouncer.setRepeatMode(Animator.REVERSE);
                ball = balls.get(3);
                pvhY = new PropertyValuesHolder("y", ball.getY(),
                        getHeight() - BALL_SIZE);
                float ballX = ball.getX();
                Keyframe kf0 = new Keyframe(0f, ballX);
                Keyframe kf1 = new Keyframe(.5f, ballX + 100f);
                Keyframe kf2 = new Keyframe(1f, ballX + 50f);
                PropertyValuesHolder pvhX = new PropertyValuesHolder("x", kf0, kf1, kf2);
                PropertyAnimator yxBouncer = new PropertyAnimator(DURATION/2, ball, pvhY, pvhX);
                yxBouncer.setRepeatCount(1);
                yxBouncer.setRepeatMode(Animator.REVERSE);
                bounceAnim = new Sequencer();
                ((Sequencer)bounceAnim).playTogether(yBouncer, yAlphaBouncer, whxyBouncer, yxBouncer);
            }
        }
        public void startAnimation() {
            createAnimation();
            bounceAnim.start();
        }
        private ShapeHolder addBall(float x, float y) {
            OvalShape circle = new OvalShape();
            circle.resize(BALL_SIZE, BALL_SIZE);
            ShapeDrawable drawable = new ShapeDrawable(circle);
            ShapeHolder shapeHolder = new ShapeHolder(drawable);
            shapeHolder.setX(x);
            shapeHolder.setY(y);
            int red = (int)(100 + Math.random() * 155);
            int green = (int)(100 + Math.random() * 155);
            int blue = (int)(100 + Math.random() * 155);
            int color = 0xff000000 | red << 16 | green << 8 | blue;
            Paint paint = drawable.getPaint();
            int darkColor = 0xff000000 | red/4 << 16 | green/4 << 8 | blue/4;
            RadialGradient gradient = new RadialGradient(37.5f, 12.5f,
                    50f, color, darkColor, Shader.TileMode.CLAMP);
            paint.setShader(gradient);
            shapeHolder.setPaint(paint);
            balls.add(shapeHolder);
            return shapeHolder;
        }
        @Override
        protected void onDraw(Canvas canvas) {
            for (ShapeHolder ball : balls) {
                canvas.translate(ball.getX(), ball.getY());
                ball.getShape().draw(canvas);
                canvas.translate(-ball.getX(), -ball.getY());
            }
        }
        public void onAnimationUpdate(Animator animation) {
            invalidate();
        }
    }
}