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      1 /*
      2  * Copyright (C) 2007 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 rate of change starts out quickly and
     32  * and then decelerates.
     33  *
     34  */
     35 @HasNativeInterpolator
     36 public class DecelerateInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
     37     public DecelerateInterpolator() {
     38     }
     39 
     40     /**
     41      * Constructor
     42      *
     43      * @param factor Degree to which the animation should be eased. Setting factor to 1.0f produces
     44      *        an upside-down y=x^2 parabola. Increasing factor above 1.0f makes exaggerates the
     45      *        ease-out effect (i.e., it starts even faster and ends evens slower)
     46      */
     47     public DecelerateInterpolator(float factor) {
     48         mFactor = factor;
     49     }
     50 
     51     public DecelerateInterpolator(Context context, AttributeSet attrs) {
     52         this(context.getResources(), context.getTheme(), attrs);
     53     }
     54 
     55     /** @hide */
     56     public DecelerateInterpolator(Resources res, Theme theme, AttributeSet attrs) {
     57         TypedArray a;
     58         if (theme != null) {
     59             a = theme.obtainStyledAttributes(attrs, R.styleable.DecelerateInterpolator, 0, 0);
     60         } else {
     61             a = res.obtainAttributes(attrs, R.styleable.DecelerateInterpolator);
     62         }
     63 
     64         mFactor = a.getFloat(R.styleable.DecelerateInterpolator_factor, 1.0f);
     65         setChangingConfiguration(a.getChangingConfigurations());
     66         a.recycle();
     67     }
     68 
     69     public float getInterpolation(float input) {
     70         float result;
     71         if (mFactor == 1.0f) {
     72             result = (float)(1.0f - (1.0f - input) * (1.0f - input));
     73         } else {
     74             result = (float)(1.0f - Math.pow((1.0f - input), 2 * mFactor));
     75         }
     76         return result;
     77     }
     78 
     79     private float mFactor = 1.0f;
     80 
     81     /** @hide */
     82     @Override
     83     public long createNativeInterpolator() {
     84         return NativeInterpolatorFactoryHelper.createDecelerateInterpolator(mFactor);
     85     }
     86 }
     87