Android移动开发-属性动画的实现

Android移动开发-属性动画的实现，该示范了如何利用属性动画来控制“小球”掉落动画，该示例会监听用户在屏幕上的“触屏”时间，程序会在屏幕的触摸点绘制一个小球，并用动画控制该小球向下掉落。

MainActivity.java

package com.fukaimei.animatortest;import android.animation.Animator;import android.animation.AnimatorListenerAdapter;import android.animation.AnimatorSet;import android.animation.ObjectAnimator;import android.animation.ValueAnimator;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.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.MotionEvent;import android.view.View;import android.view.animation.AccelerateInterpolator;import android.widget.LinearLayout;import java.util.ArrayList;public class MainActivity extends AppCompatActivity {    // 定义小球大小的常量    static final float BALL_SIZE = 50F;    // 定义小球从屏幕上方下落到屏幕底端的总时间    static final float FULL_TIME = 1000;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        LinearLayout container = (LinearLayout) findViewById(R.id.container);        // 设置该窗口显示MyAnimationView组件        container.addView(new MyAnimationView(this));    }    public class MyAnimationView extends View implements ValueAnimator.AnimatorUpdateListener {        public final ArrayList<ShapeHolder> balls = new ArrayList<ShapeHolder>();        public MyAnimationView(Context context) {            super(context);            setBackgroundColor(Color.WHITE);        }        @Override        public boolean onTouchEvent(MotionEvent event) {            // 如果触碰事件不是按下、移动事件            if (event.getAction() != MotionEvent.ACTION_DOWN &&                    event.getAction() != MotionEvent.ACTION_MOVE) {                return false;            }            //  在事件发生点添加一个小球（用一个圆形代表）            ShapeHolder newBall = addBall(event.getX(), event.getY());            // 计算小球下落动画开始时的y坐标            float startY = newBall.getY();            // 计算小球下落动画结束时的y坐标（落到屏幕最下方，就是屏幕高度减去小球高度）            float endY = getHeight() - BALL_SIZE;            // 获取屏幕高度            float h = (float) getHeight();            float eventY = event.getY();            // 计算动画的持续时间            int duration = (int) (FULL_TIME * ((h - eventY) / h));            // 定义小球“落下”的动画：            // 让newBall对象的y属性从事件发生点变化到屏幕最下方            ValueAnimator fallAnim = ObjectAnimator.ofFloat(newBall, "y", startY, endY);            // 设置fallAnim动画的持续时间            fallAnim.setDuration(duration);            // 设置fallAnim动画的插值方式：加速插值            fallAnim.setInterpolator(new AccelerateInterpolator());            // 为fallAnim动画添加监听器            // 当ValueAnimator的属性值发生改变时，将会激发该监听器的事件监听方法            fallAnim.addUpdateListener(this);            // 定义对newBall对象的alpha属性执行从1到0的动画（即定义渐隐动画）            ObjectAnimator fadeAnim = ObjectAnimator.ofFloat(newBall, "alpha", 1f, 0f);            // 设置动画持续时间            fadeAnim.setDuration(250);            // 为fadeAnim动画添加监听器            fadeAnim.addListener(new AnimatorListenerAdapter() {                // 当动画结束时                @Override                public void onAnimationEnd(Animator animation) {                    // 动画结束时将该动画关联的ShapeHolder删除                    balls.remove(((ObjectAnimator) animation).getTarget());                }            });            // 为fadeAnim动画添加监听器            // 当ValueAnimator的属性值发生改变时，将会激发该监听器的事件监听方法            fadeAnim.addUpdateListener(this);            // 定义一个AnimatorSet来组合动画            AnimatorSet animatorSet = new AnimatorSet();            // 指定在播放fadeAnim之前，先播放fallAnim动画            animatorSet.play(fallAnim).before(fadeAnim);            // 开始播放动画            animatorSet.start();            return true;        }        private ShapeHolder addBall(float x, float y) {            // 创建一个椭圆            OvalShape circle = new OvalShape();            // 设置该椭圆的宽和高            circle.resize(BALL_SIZE, BALL_SIZE);            // 将椭圆包装成Drawable对象            ShapeDrawable drawable = new ShapeDrawable(circle);            // 创建一个ShapeHolder对象            ShapeHolder shapeHolder = new ShapeHolder(drawable);            // 设置ShapeHolder的x、y坐标            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);            // 将red、green、blue三个随机数组合成ARGB颜色            int color = 0xff000000 + red << 16 | green << 8 | blue;            // 获取drawable上关联的画笔            Paint paint = drawable.getPaint();            // 将red、green、blue三个随机数除以4得到商值组合成ARGB颜色            int darkColor = 0xff000000 | red / 4 << 16                    | green / 4 << 8 | blue / 4;            // 创建圆形渐变            RadialGradient gradient = new RadialGradient(37.5f, 12.5f,                    BALL_SIZE, color, darkColor, Shader.TileMode.CLAMP);            paint.setShader(gradient);            // 为shapeHolder设置paint画笔            shapeHolder.setPaint(paint);            balls.add(shapeHolder);            return shapeHolder;        }        @Override        protected void onDraw(Canvas canvas) {            // 遍历balls集合中的每个ShapeHolder对象            for (ShapeHolder shapeHolder : balls) {                // 保存canvas的当前坐标系统                canvas.save();                // 坐标变换：将画布坐标系统平移到shapeHolder的X、Y坐标处                canvas.translate(shapeHolder.getX(), shapeHolder.getY());                // 将shapeHolder持有的圆形绘制在Canvas上                shapeHolder.getShape().draw(canvas);                // 恢复Canvas坐标系统                canvas.restore();            }        }        @Override        public void onAnimationUpdate(ValueAnimator animation) {            // 指定重绘该界面            this.invalidate();        }    }}

ShapeHolder.java

package com.fukaimei.animatortest;import android.graphics.Paint;import android.graphics.RadialGradient;import android.graphics.drawable.ShapeDrawable;/** * Created by FuKaimei on 2017/9/17. */public class ShapeHolder {    private float x = 0, y = 0;    private ShapeDrawable shape;    private int color;    private RadialGradient gradient;    private float alpha = 1f;    private Paint paint;    public ShapeHolder(ShapeDrawable s) {        shape = s;    }    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 getShape() {        return shape;    }    public void setShape(ShapeDrawable shape) {        this.shape = shape;    }    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;    }}

源码下载地址：
http://download.csdn.net/download/fukaimei/9982420