用属性动画实现小球的落地和弹起

所有代码如下：

package com.example.animation;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.AnimatorSet;
import android.animation.ObjectAnimator;
import android.animation.ValueAnimator;
import android.animation.ValueAnimator.AnimatorUpdateListener;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RadialGradient;
import android.graphics.Shader;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.OvalShape;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.view.animation.DecelerateInterpolator;
import android.widget.LinearLayout;

import java.util.ArrayList;

public class AnimatorTest extends Activity {
    static final float BALL_SIZE = 50f;
    static final float FULL_TIME = 500;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        LinearLayout container = new LinearLayout(this);
        ViewGroup.LayoutParams lp = new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.MATCH_PARENT);
        container.addView(new MyAnimationView(this), lp);
        setContentView(container);

    }

    public class MyAnimationView extends View implements AnimatorUpdateListener {

        public final ArrayList<ShapeHolder> balls = new ArrayList<ShapeHolder>();

        public MyAnimationView(Context context) {
            super(context);
            setBackgroundColor(Color.WHITE);
        }

        @Override
        protected void onDraw(Canvas canvas) {
            for (ShapeHolder shapeHolder : balls) {
                canvas.save();

                canvas.translate(shapeHolder.getX(), shapeHolder.getY());
                shapeHolder.getShap().draw(canvas);
                canvas.restore();

            }

        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {
            if (event.getAction() != MotionEvent.ACTION_DOWN
                    && event.getAction() != MotionEvent.ACTION_MOVE) {
                return false;

            }
            ShapeHolder newBall = addBall(event.getX(), event.getY());

            float h = getHeight();// 屏幕高度
            float startY = newBall.getY();
            float endY = h - BALL_SIZE;

            int duration = (int) (FULL_TIME * ((h - event.getY()) / h));
            if (duration < 0) {
                duration = 0;
            }

            // 定义下落的属性动画/////////////////////////////////////////////////////////////////////////
            ValueAnimator fallAnim = ObjectAnimator.ofFloat(newBall, "y", startY, endY);
            fallAnim.setDuration(duration);
            fallAnim.setInterpolator(new AccelerateDecelerateInterpolator());// 加速插值
            fallAnim.addUpdateListener(this);

            // 定义小球压扁的属性动画:画布位置左移，宽度拉长/////////////////////////////////////////////////////////////////////////
            ValueAnimator squashAnim1 = ObjectAnimator.ofFloat(newBall, "x", newBall.getX(),
                    newBall.getX() - BALL_SIZE / 2);
            squashAnim1.setDuration(duration / 4);
            squashAnim1.setInterpolator(new DecelerateInterpolator());
            squashAnim1.setRepeatCount(1);
            squashAnim1.setRepeatMode(ValueAnimator.REVERSE);
            squashAnim1.addUpdateListener(this);

            ValueAnimator squashAnim2 = ObjectAnimator.ofFloat(newBall, "width",
                    newBall.getWidth(),
                    newBall.getWidth() + BALL_SIZE / 2);
            squashAnim2.setDuration(duration / 4);
            squashAnim2.setInterpolator(new DecelerateInterpolator());
            squashAnim2.setRepeatCount(1);
            squashAnim2.setRepeatMode(ValueAnimator.REVERSE);
            squashAnim2.addUpdateListener(this);
            // 定义小球拉伸的属性动画:画布位置下移，高度压低/////////////////////////////////////////////////////////////////////////
            ValueAnimator stretchAnim1 = ObjectAnimator.ofFloat(newBall, "y",
                    endY,
                    endY + BALL_SIZE / 2);
            stretchAnim1.setDuration(duration / 4);
            stretchAnim1.setInterpolator(new DecelerateInterpolator());
            stretchAnim1.setRepeatCount(1);
            stretchAnim1.setRepeatMode(ValueAnimator.REVERSE);
            stretchAnim1.addUpdateListener(this);

            ValueAnimator stretchAnim2 = ObjectAnimator.ofFloat(newBall, "height",
                    newBall.getHeight(),
                    newBall.getHeight() - BALL_SIZE / 2);
            stretchAnim2.setDuration(duration / 4);
            stretchAnim2.setInterpolator(new DecelerateInterpolator());
            stretchAnim2.setRepeatCount(1);
            stretchAnim2.setRepeatMode(ValueAnimator.REVERSE);
            stretchAnim2.addUpdateListener(this);
            // 定义小球弹起的属性动画://///////////////////////////////////////////////////////////////////////
            ValueAnimator bounceBackAnim = ObjectAnimator.ofFloat(newBall, "y",
                    endY,
                    startY);
            bounceBackAnim.setDuration(duration);
            bounceBackAnim.setInterpolator(new DecelerateInterpolator());
            bounceBackAnim.addUpdateListener(this);

            // 定义渐隐的属性动画/////////////////////////////////////////////////////////////////////////
            ObjectAnimator fadeAnim = ObjectAnimator.ofFloat(newBall, "alpha", 1f, 0f);
            fadeAnim.setDuration(250);
            fadeAnim.addUpdateListener(this);
            fadeAnim.addListener(new AnimatorListenerAdapter() {

                @Override
                public void onAnimationEnd(Animator animation) {
                    balls.remove(((ObjectAnimator) animation).getTarget());
                }

            });

            // 定义属性动画集合：掉落--压扁&拉伸--弹起/////////////////////////////////////////////////////////////////////////
            AnimatorSet bouncer = new AnimatorSet();
            bouncer.play(fallAnim).before(squashAnim1);
            bouncer.play(squashAnim1).with(squashAnim2).with(stretchAnim1).with(stretchAnim2);
            bouncer.play(bounceBackAnim).after(squashAnim1);
            // 属性动画集合，将上面的bouncer和fadeAnim组合起来，并安排顺序
            AnimatorSet set = new AnimatorSet();
            set.play(bouncer).before(fadeAnim);
            set.start();

            return true;
        }

        @Override
        public void onAnimationUpdate(ValueAnimator animation) {
            this.invalidate();

        }

        public ShapeHolder addBall(float x, float y) {

            OvalShape circle = new OvalShape();
            circle.resize(BALL_SIZE, BALL_SIZE);
            ShapeDrawable shape = new ShapeDrawable(circle);// 将圆包装成drawable对象
            ShapeHolder shapeHolder = new ShapeHolder(shape);

            shapeHolder.setX(x - BALL_SIZE / 2);
            shapeHolder.setY(y - BALL_SIZE / 2);

            int red = (int) (Math.random() * 255);
            int green = (int) (Math.random() * 255);
            int blue = (int) (Math.random() * 255);

            int color = 0xff000000 + ((red << 16) | (green << 8) | blue);
            int darkColor = 0xff000000 + (((red / 4) << 16) | (green / 4 << 8) | (blue / 4));

            Paint paint = shape.getPaint();
            RadialGradient radialGradient = new RadialGradient(x, y, BALL_SIZE, color, darkColor,
                    Shader.TileMode.CLAMP);
            paint.setShader(radialGradient);

            shapeHolder.setPaint(paint);

            balls.add(shapeHolder);

            return shapeHolder;
        }

    }

}

package com.example.animation;

import android.graphics.Paint;
import android.graphics.RadialGradient;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.Shape;

public class ShapeHolder {
    private float x = 0, y = 0;// 注意此处的x和y是画布开始的位置
    private ShapeDrawable shap;
    private int color;
    private RadialGradient gradient; // 环形渐变
    private float alpha = 1f;
    private Paint paint;

    ShapeHolder(ShapeDrawable s) {
        this.shap = s;
    }

    public float getWidth() {
        return shap.getShape().getWidth();
    }

    public void setWidth(float width) {
        Shape s = shap.getShape();
        s.resize(width, s.getHeight());
    }

    public float getHeight() {
        return shap.getShape().getHeight();
    }

    public void setHeight(float height) {
        Shape s = shap.getShape();
        s.resize(s.getWidth(), height);
    }

    public float getX() {
        return x;
    }

    public void setX(float x) {
        this.x = x;
    }

    public float getY() {
        return y;
    }

    public void setY(float y) {
        this.y = y;
    }

    public ShapeDrawable getShap() {
        return shap;
    }

    public void setShap(ShapeDrawable shap) {
        this.shap = shap;
    }

    public int getColor() {
        return color;
    }

    public void setColor(int color) {
        this.color = color;
    }

    public RadialGradient getGradient() {
        return gradient;
    }

    public void setGradient(RadialGradient gradient) {
        this.gradient = gradient;
    }

    public float getAlpha() {
        return alpha;
    }

    public void setAlpha(float alpha) {
        this.alpha = alpha;
    }

    public Paint getPaint() {
        return paint;
    }

    public void setPaint(Paint paint) {
        this.paint = paint;
    }

}