实现爱心满天飞的效果

最近需要完成这样的一个效果：

sdasd.gif

看上去就是动画跟贝塞尔曲线的组合，但是因为动画不熟悉，所以比较难以实现，这里的代码是摘取至 hcc大神的分享

LoveLikeLayout：

public class LoveLikeLayout extends RelativeLayout {

    //线性插值器
    private Interpolator line = new LinearInterpolator();

    //加速插值器
    private Interpolator acc = new AccelerateInterpolator();

    //减速插值器
    private Interpolator dce = new DecelerateInterpolator();

    //先加速后减速插值器
    private Interpolator accdec = new AccelerateDecelerateInterpolator();

    //插值器数组
    private Interpolator[] interpolators;

    //随机数
    private Random mRandom = new Random();

    //爱心图片数组
    private Drawable[] drawables;

    //爱心图片的高度
    private int drawableHeight;

    //爱心图片的宽度
    private int drawableWidth;

    //参数值
    private LayoutParams layoutParams;

    //layout高度
    private int measuredHeight;

    //layout宽度
    private int measuredWidth;

    public LoveLikeLayout(Context context) {
        this(context, null);
    }

    public LoveLikeLayout(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public LoveLikeLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    /**
     * 初始化
     */
    private void init() {
        //初始化爱心图片
        drawables = new Drawable[3];
        Drawable red = getResources().getDrawable(R.drawable.pl_red);
        Drawable yellow = getResources().getDrawable(R.drawable.pl_yellow);
        Drawable blue = getResources().getDrawable(R.drawable.pl_blue);
        drawables[0] = red;
        drawables[1] = yellow;
        drawables[2] = blue;

        //获取爱心的宽高
        drawableHeight = red.getIntrinsicHeight();
        drawableWidth = red.getIntrinsicWidth();

        //设置爱心的显示位置
        layoutParams = new LayoutParams(drawableWidth, drawableHeight);
        layoutParams.addRule(CENTER_HORIZONTAL, TRUE);
        layoutParams.addRule(ALIGN_PARENT_BOTTOM, TRUE);

        //初始化动画插值器
        interpolators = new Interpolator[4];
        interpolators[0] = line;
        interpolators[1] = acc;
        interpolators[2] = dce;
        interpolators[3] = accdec;
    }

    /**
     * 测量layout的宽高
     * 用于计算爱心的显示位置
     *
     * @param widthMeasureSpec
     * @param heightMeasureSpec
     */
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        measuredHeight = getMeasuredHeight();
        measuredWidth = getMeasuredWidth();
    }

    /**
     * 显示爱心
     */
    public void addLove() {
        final ImageView imageView = new ImageView(getContext());
        //随机生成爱心颜色
        imageView.setImageDrawable(drawables[mRandom.nextInt(3)]);
        imageView.setLayoutParams(layoutParams);

        addView(imageView);
        Animator animtor = getAnimtor(imageView);
        animtor.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                removeView(imageView);
                super.onAnimationEnd(animation);
            }
        });
        animtor.start();
    }


    /**
     * 爱心的显示和运行轨迹动画组合实现
     *
     * @param target
     * @return
     */
    private Animator getAnimtor(View target) {
        AnimatorSet enterAnimtorSet = getEnterAnimtorSet(target);
        ValueAnimator bezierAnimtor = getBezierAnimtor(target);

        AnimatorSet animatorSet = new AnimatorSet();
        animatorSet.playSequentially(enterAnimtorSet);
        animatorSet.playSequentially(enterAnimtorSet, bezierAnimtor);
        animatorSet.setInterpolator(interpolators[mRandom.nextInt(4)]);
        animatorSet.setTarget(target);

        return animatorSet;
    }


    /**
     * 爱心的显示动画实现
     *
     * @param target
     * @return
     */
    private AnimatorSet getEnterAnimtorSet(View target) {
        //爱心的3中动画组合 透明度 x，y轴的缩放
        ObjectAnimator alpha = ObjectAnimator.ofFloat(target, View.ALPHA, 0.2f, 1f);
        ObjectAnimator scaleX = ObjectAnimator.ofFloat(target, View.SCALE_X, 0.2f, 1f);
        ObjectAnimator scaleY = ObjectAnimator.ofFloat(target, View.SCALE_Y, 0.2f, 1f);

        //组合动画
        AnimatorSet set = new AnimatorSet();
        set.setDuration(500);
        set.setInterpolator(new LinearInterpolator());
        set.playTogether(alpha, scaleX, scaleY);
        set.setTarget(target);

        return set;
    }


    /**
     * 爱心运动轨迹的动画实现
     *
     * @param target
     * @return
     */
    private ValueAnimator getBezierAnimtor(final View target) {
        BezierEvaluator evaluator = new BezierEvaluator(getPoint(2), getPoint(1));

        ValueAnimator animator = ValueAnimator.ofObject(evaluator,
                new PointF((measuredWidth - drawableWidth) / 2, measuredHeight - drawableHeight),
                new PointF(mRandom.nextInt(getWidth()), 0));


        animator.setDuration(3000);
        animator.setTarget(target);
        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator valueAnimator) {
                //获取贝塞尔曲线的运动轨迹 让爱心跟随着移动
                PointF animatedValue = (PointF) valueAnimator.getAnimatedValue();
                target.setX(animatedValue.x);
                target.setY(animatedValue.y);
                //增加透明度的变化
                target.setAlpha(1 - valueAnimator.getAnimatedFraction());
            }
        });

        return animator;
    }

    /**
     * 获取中间的两个点
     *
     * @return
     */
    private PointF getPoint(int scale) {
        PointF pointF = new PointF();
        pointF.x = mRandom.nextInt((measuredWidth - 100));
        pointF.y = mRandom.nextInt((measuredHeight - 100)) / scale;
        return pointF;
    }
}

BezierEvaluator：

public class BezierEvaluator implements TypeEvaluator<PointF> {


    private PointF pointF1;
    private PointF pointF2;

    public BezierEvaluator(PointF pointF1, PointF pointF2) {
        this.pointF1 = pointF1;
        this.pointF2 = pointF2;
    }

    @Override
    public PointF evaluate(float time, PointF startValue, PointF endValue) {

        float timeLeft = 1.0f - time;
        PointF point = new PointF();//结果

        point.x = timeLeft * timeLeft * timeLeft * (startValue.x)
                + 3 * timeLeft * timeLeft * time * (pointF1.x)
                + 3 * timeLeft * time * time * (pointF2.x)
                + time * time * time * (endValue.x);

        point.y = timeLeft * timeLeft * timeLeft * (startValue.y)
                + 3 * timeLeft * timeLeft * time * (pointF1.y)
                + 3 * timeLeft * time * time * (pointF2.y)
                + time * time * time * (endValue.y);
        return point;
    }
}

用法：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:background="#80000000"
    android:layout_height="match_parent"
    android:orientation="vertical">


    <com.stay4it.widgets.ui.LoveLikeLayout
        android:id="@+id/id_LoveLikeLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1" />

    <Button
        android:id="@+id/btn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="点击" />
</LinearLayout>


public class LoveActivity extends AppCompatActivity {
    private LoveLikeLayout mLoveLikeLayout;
    private Button btn;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_love);
        mLoveLikeLayout = (LoveLikeLayout) findViewById(R.id.id_LoveLikeLayout);
        btn = (Button) findViewById(R.id.btn);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mLoveLikeLayout.addLove();
            }
        });
    }

先把代码摘录下来，后面再研究。。

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