PointTypeEvaluatorView.java

package com.cui.trypro.widget;

import android.animation.TypeEvaluator;
import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;

import com.cui.trypro.bean.Point;

/**
 * http://mp.weixin.qq.com/s?__biz=MzA3MDMyMjkzNg==&mid=211126926&idx=2&sn=aa82e1eeb673b0590c5b9b7aee1f0c70&scene=23&srcid=WUOuK4Mun4DUxrxK3Sh5#rd
 * Created by cuiyang on 15/8/28.
 */
public class PointTypeEvaluatorView extends View {
    public static final float RADIUS = 50f;

    private Point currentPoint;

    private Paint mPaint;


    public PointTypeEvaluatorView(Context context) {
        super(context);
        init();
    }

    public PointTypeEvaluatorView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();

    }

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

    }

    private void init() {
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setColor(Color.BLUE);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (currentPoint == null) {
            currentPoint = new Point(RADIUS, RADIUS);
            drawCircle(canvas);
            startAnimation();
        } else {
            drawCircle(canvas);

        }

    }

    private void drawCircle(Canvas canvas) {
        float x = currentPoint.getX();
        float y = currentPoint.getY();
        canvas.drawCircle(x, y, RADIUS, mPaint);
    }

    private void startAnimation() {
        Point startPoint = new Point(RADIUS, RADIUS);
        Point endPoint = new Point(getWidth() - RADIUS, getHeight() - RADIUS);
        ValueAnimator anim = ValueAnimator.ofObject(new PointEvaluator(), startPoint, endPoint);
        anim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                currentPoint = (Point) animation.getAnimatedValue();
                invalidate();
            }
        });
        anim.setDuration(5000);
        anim.start();
    }

    public class PointEvaluator implements TypeEvaluator {

        @Override
        public Object evaluate(float fraction, Object startValue, Object endValue) {
            Point startPoint = (Point) startValue;
            Point endPoint = (Point) endValue;
            float x = startPoint.getX() + fraction * (endPoint.getX() - startPoint.getX());
            float y = startPoint.getY() + fraction * (endPoint.getY() - startPoint.getY());
            Point point = new Point(x, y);
            return point;
        }

    }

    /**
     * FloatEvaluator实现了TypeEvaluator接口，然后重写evaluate()方法。evaluate()方法当中传入了三个参数，第
     * 一个参数fraction非常重要，这个参数用于表示动画的完成度的，我们应该根据它来计算当前动画的值应该是多少，
     * 第二第三个参数分别表示动画的初始值和结束值。那么上述代码的逻辑就比较清晰了，用结束值减去初始值，算出它们
     * 之间的差值，然后乘以fraction这个系数，再加上初始值，那么就得到当前动画的值了。
     *
     *
     *
     * PointEvaluator同样实现了TypeEvaluator接口并重写了evaluate()方法。其实evaluate()方法中的逻辑还是非常
     * 简单的，
     * 先是将startValue和endValue强转成Point对象，然后同样根据fraction来计算当前动画的x和y的值，最后组装到一
     * 个新的Point对象当中并返回。

     这样我们就将PointEvaluator编写完成了，接下来我们就可以非常轻松地对Point对象进行动画操作了，比如说我们有两
     个Point对象，现在需要将Point1通过动画平滑过度到Point2，就可以这样写：*/
}