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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.content.res.Resources;
     21 import android.content.res.Resources.Theme;
     22 import android.content.res.TypedArray;
     23 import android.util.AttributeSet;
     24 
     25 import com.android.internal.R;
     26 import com.android.internal.view.animation.HasNativeInterpolator;
     27 import com.android.internal.view.animation.NativeInterpolatorFactory;
     28 import com.android.internal.view.animation.NativeInterpolatorFactoryHelper;
     29 
     30 /**
     31  * An interpolator where the change flings forward and overshoots the last value
     32  * then comes back.
     33  */
     34 @HasNativeInterpolator
     35 public class OvershootInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
     36     private final float mTension;
     37 
     38     public OvershootInterpolator() {
     39         mTension = 2.0f;
     40     }
     41 
     42     /**
     43      * @param tension Amount of overshoot. When tension equals 0.0f, there is
     44      *                no overshoot and the interpolator becomes a simple
     45      *                deceleration interpolator.
     46      */
     47     public OvershootInterpolator(float tension) {
     48         mTension = tension;
     49     }
     50 
     51     public OvershootInterpolator(Context context, AttributeSet attrs) {
     52         this(context.getResources(), context.getTheme(), attrs);
     53     }
     54 
     55     /** @hide */
     56     public OvershootInterpolator(Resources res, Theme theme, AttributeSet attrs) {
     57         TypedArray a;
     58         if (theme != null) {
     59             a = theme.obtainStyledAttributes(attrs, R.styleable.OvershootInterpolator, 0, 0);
     60         } else {
     61             a = res.obtainAttributes(attrs, R.styleable.OvershootInterpolator);
     62         }
     63 
     64         mTension = a.getFloat(R.styleable.OvershootInterpolator_tension, 2.0f);
     65         setChangingConfiguration(a.getChangingConfigurations());
     66         a.recycle();
     67     }
     68 
     69     public float getInterpolation(float t) {
     70         // _o(t) = t * t * ((tension + 1) * t + tension)
     71         // o(t) = _o(t - 1) + 1
     72         t -= 1.0f;
     73         return t * t * ((mTension + 1) * t + mTension) + 1.0f;
     74     }
     75 
     76     /** @hide */
     77     @Override
     78     public long createNativeInterpolator() {
     79         return NativeInterpolatorFactoryHelper.createOvershootInterpolator(mTension);
     80     }
     81 }
     82