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      1 /*
      2  * Copyright (C) 2009 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.view.animation;
     18 
     19 import android.content.Context;
     20 import android.util.AttributeSet;
     21 
     22 import com.android.internal.view.animation.HasNativeInterpolator;
     23 import com.android.internal.view.animation.NativeInterpolatorFactory;
     24 import com.android.internal.view.animation.NativeInterpolatorFactoryHelper;
     25 
     26 /**
     27  * An interpolator where the change bounces at the end.
     28  */
     29 @HasNativeInterpolator
     30 public class BounceInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
     31     public BounceInterpolator() {
     32     }
     33 
     34     @SuppressWarnings({"UnusedDeclaration"})
     35     public BounceInterpolator(Context context, AttributeSet attrs) {
     36     }
     37 
     38     private static float bounce(float t) {
     39         return t * t * 8.0f;
     40     }
     41 
     42     public float getInterpolation(float t) {
     43         // _b(t) = t * t * 8
     44         // bs(t) = _b(t) for t < 0.3535
     45         // bs(t) = _b(t - 0.54719) + 0.7 for t < 0.7408
     46         // bs(t) = _b(t - 0.8526) + 0.9 for t < 0.9644
     47         // bs(t) = _b(t - 1.0435) + 0.95 for t <= 1.0
     48         // b(t) = bs(t * 1.1226)
     49         t *= 1.1226f;
     50         if (t < 0.3535f) return bounce(t);
     51         else if (t < 0.7408f) return bounce(t - 0.54719f) + 0.7f;
     52         else if (t < 0.9644f) return bounce(t - 0.8526f) + 0.9f;
     53         else return bounce(t - 1.0435f) + 0.95f;
     54     }
     55 
     56     /** @hide */
     57     @Override
     58     public long createNativeInterpolator() {
     59         return NativeInterpolatorFactoryHelper.createBounceInterpolator();
     60     }
     61 }