ElasticOutInterpolator.java

/*
 * Copyright (C) 2016 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.android.apps.santatracker.doodles.shared;

import android.view.animation.Interpolator;

/**
 * An interpolator which has a rubber bound effect around its end point, bouncing back and forth
 * before settling at its final value.
 *
 * Implementation copied from outElastic here: https://goo.gl/SJZllG
 */
public class ElasticOutInterpolator implements Interpolator {

  private final float period;

  public ElasticOutInterpolator() {
    period = 0.4f;
  }

  public ElasticOutInterpolator(float period) {
    this.period = period;
  }

  @Override
  public float getInterpolation(float value) {
    return (float) (Math.pow(2, -10 * value)
        * Math.sin((value - period / 4) * (2 * Math.PI) / period) + 1);
  }
}