BezierEvaluator.java

package yifeiyuan.practice.practicedemos.periscope;

import android.animation.TypeEvaluator;
import android.graphics.PointF;

/**
 * Created by yifeiyuan on 15/6/18.
 */
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;
    }
}