content: /*
   * Copyright (C) 2009 The Android Open Source Project
   *
   * 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 android.view.animation;
  
  import static com.android.internal.R.styleable.AnticipateOvershootInterpolator;
  import static com.android.internal.R.styleable.AnticipateOvershootInterpolator_extraTension;
  import static com.android.internal.R.styleable.AnticipateOvershootInterpolator_tension;
  
  import android.content.Context;
  import android.content.res.Resources;
  import android.content.res.Resources.Theme;
  import android.content.res.TypedArray;
  import android.util.AttributeSet;
  
  import com.android.internal.view.animation.HasNativeInterpolator;
  import com.android.internal.view.animation.NativeInterpolatorFactory;
  import com.android.internal.view.animation.NativeInterpolatorFactoryHelper;
  
  /**
   * An interpolator where the change starts backward then flings forward and overshoots
   * the target value and finally goes back to the final value.
   */
  @HasNativeInterpolator
  public class AnticipateOvershootInterpolator extends BaseInterpolator
          implements NativeInterpolatorFactory {
      private final float mTension;
  
      public AnticipateOvershootInterpolator() {
          mTension = 2.0f * 1.5f;
      }
  
      /**
       * @param tension Amount of anticipation/overshoot. When tension equals 0.0f,
       *                there is no anticipation/overshoot and the interpolator becomes
       *                a simple acceleration/deceleration interpolator.
       */
      public AnticipateOvershootInterpolator(float tension) {
          mTension = tension * 1.5f;
      }
  
      /**
       * @param tension Amount of anticipation/overshoot. When tension equals 0.0f,
       *                there is no anticipation/overshoot and the interpolator becomes
       *                a simple acceleration/deceleration interpolator.
       * @param extraTension Amount by which to multiply the tension. For instance,
       *                     to get the same overshoot as an OvershootInterpolator with
       *                     a tension of 2.0f, you would use an extraTension of 1.5f.
       */
      public AnticipateOvershootInterpolator(float tension, float extraTension) {
          mTension = tension * extraTension;
      }
  
      public AnticipateOvershootInterpolator(Context context, AttributeSet attrs) {
          this(context.getResources(), context.getTheme(), attrs);
      }
  
      /** @hide */
      public AnticipateOvershootInterpolator(Resources res, Theme theme, AttributeSet attrs) {
          TypedArray a;
          if (theme != null) {
              a = theme.obtainStyledAttributes(attrs, AnticipateOvershootInterpolator, 0, 0);
          } else {
              a = res.obtainAttributes(attrs, AnticipateOvershootInterpolator);
          }
  
          mTension = a.getFloat(AnticipateOvershootInterpolator_tension, 2.0f) *
                  a.getFloat(AnticipateOvershootInterpolator_extraTension, 1.5f);
          setChangingConfiguration(a.getChangingConfigurations());
          a.recycle();
      }
  
      private static float a(float t, float s) {
          return t * t * ((s + 1) * t - s);
      }
  
      private static float o(float t, float s) {
          return t * t * ((s + 1) * t + s);
      }
  
      public float getInterpolation(float t) {
          // a(t, s) = t * t * ((s + 1) * t - s)
          // o(t, s) = t * t * ((s + 1) * t + s)
          // f(t) = 0.5 * a(t * 2, tension * extraTension), when t < 0.5
          // f(t) = 0.5 * (o(t * 2 - 2, tension * extraTension) + 2), when t <= 1.0
          if (t < 0.5f) return 0.5f * a(t * 2.0f, mTension);
          else return 0.5f * (o(t * 2.0f - 2.0f, mTension) + 2.0f);
      }
  
      /** @hide */
      @Override
      public long createNativeInterpolator() {
          return NativeInterpolatorFactoryHelper.createAnticipateOvershootInterpolator(mTension);
      }
  }
  