前言

在上一篇 动画实战：打造炫酷的加载动画 中，我们利用属性动画打造了较为炫酷的加载动画，本篇文章还是以属性动画为利器，结合自定义 View/ViewGroup 打造仿某搜索引擎搜索中的动画效果。

1.效果分析

1.1 效果图

loading

1.2 效果分析

三个点，每次回到中间会交换颜色，属性动画控制运动

2.实现分析

RelativeLayout里面添加3个View(圆形)，结合属性动画去反复运动，监听动画执行在合适的时间去交换颜色

画圆：CircleView

public class CircleView extends View {
    private Paint mPaint;
    private int mColor;
    public CircleView(Context context) {
        this(context,null);
    }

    public CircleView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs,0);
    }

    public CircleView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        // 画背景圆形 三个参数  cx cy  半径 画笔
        int cx = getWidth()/2;
        int cy = getHeight()/2;
        canvas.drawCircle(cx,cy,cx,mPaint);
    }

    /**
     * 切换颜色
     * @param color
     */
    public void exchangeColor(int color){
        mColor = color;
        mPaint.setColor(color);
        invalidate();
    }

    /**
     * 获取当前的颜色
     * @return
     */
    public int getColor() {
        return mColor;
    }
}

实现加载动画的 View：LoadingView

public class LoadingView extends RelativeLayout{
    private CircleView mLeftView,mMiddleView,mRightView;
    private int mTranslationDistance = 30;
    private final long ANIMATION_TIME = 350;
    private boolean mIsStopAnimator = false;

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

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

    public LoadingView(Context context, AttributeSet attrs, int defStyleAttr) {// LayoutInflater里面
        super(context, attrs, defStyleAttr);
        mTranslationDistance = dip2px(mTranslationDistance);

        setBackgroundColor(Color.WHITE);
        // 添加三个View 但是要圆形
        mLeftView = getCircleView(context);
        mLeftView.exchangeColor(Color.BLUE);
        mMiddleView = getCircleView(context);
        mMiddleView.exchangeColor(Color.RED);
        mRightView = getCircleView(context);
        mRightView.exchangeColor(Color.GREEN);
        addView(mLeftView);
        addView(mRightView);
        addView(mMiddleView);

        post(new Runnable() {
            @Override
            public void run() {
                // 让布局实例化好之后再去开启动画
                expendAnimation();
            }
        });
    }

    /**
     * 展开动画
     */
    private void expendAnimation() {
        if (mIsStopAnimator) {
            return;
        }
        // 左边跑
        ObjectAnimator leftTranslationAnimator = ObjectAnimator.ofFloat(mLeftView,"translationX",0,-mTranslationDistance);
        // 右边跑
        ObjectAnimator rightTranslationAnimator = ObjectAnimator.ofFloat(mRightView,"translationX",0,mTranslationDistance);

        // 弹性效果  荡秋千一样 差值器   刚开始快越来越慢

        AnimatorSet set = new AnimatorSet();
        set.setDuration(ANIMATION_TIME);
        set.playTogether(leftTranslationAnimator,rightTranslationAnimator);
        set.setInterpolator(new DecelerateInterpolator());
        set.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                // 往里面跑
                innerAnimation();
            }
        });
        set.start();
    }

    private void innerAnimation() {
        if (mIsStopAnimator) {
            return;
        }
        // 左边跑
        ObjectAnimator leftTranslationAnimator = ObjectAnimator.ofFloat(mLeftView,"translationX",-mTranslationDistance,0);
        // 右边跑
        ObjectAnimator rightTranslationAnimator = ObjectAnimator.ofFloat(mRightView,"translationX",mTranslationDistance,0);
        AnimatorSet set = new AnimatorSet();
        set.setInterpolator(new AccelerateInterpolator());
        set.setDuration(ANIMATION_TIME);
        set.playTogether(leftTranslationAnimator,rightTranslationAnimator);
        set.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                // 往里外面跑
                // 切换颜色顺序  左边的给中间 中间的给右边  右边的给左边
                int leftColor = mLeftView.getColor();
                int rightColor = mRightView.getColor();
                int middleColor = mMiddleView.getColor();
                mMiddleView.exchangeColor(leftColor);
                mRightView.exchangeColor(middleColor);
                mLeftView.exchangeColor(rightColor);
                expendAnimation();
            }
        });
        set.start();
    }

    public CircleView getCircleView(Context context) {
        CircleView circleView = new CircleView(context);
        RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(dip2px(10),dip2px(10));
        params.addRule(CENTER_IN_PARENT);
        circleView.setLayoutParams(params);
        return circleView;
    }

    private int dip2px(int dip) {
        return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,dip,getResources().getDisplayMetrics());
    }

    @Override
    public void setVisibility(int visibility) {
        super.setVisibility(View.INVISIBLE);// 不要再去排放和计算，少走一些系统的源码（View的绘制流程）
        // 清理动画
        mLeftView.clearAnimation();
        mRightView.clearAnimation();
        // 把LoadingView从父布局移除
        ViewGroup parent = (ViewGroup) getParent();
        if (parent != null) {
            parent.removeView(this);// 从父布局移除
            removeAllViews();// 移除自己所有的View
        }
        mIsStopAnimator = true;
    }
}

3.总结

在自定义 View/ViewGroup 时，如果内部有进行动画的效果处理，要注意内存的优化，往往需要如上面 setVisibility() 方法中的处理方式。