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      1 /*
      2  * Copyright (C) 2006 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 slowly and
     32  * and then accelerates.
     33  *
     34  */
     35 @HasNativeInterpolator
     36 public class AccelerateInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
     37     private final float mFactor;
     38     private final double mDoubleFactor;
     39 
     40     public AccelerateInterpolator() {
     41         mFactor = 1.0f;
     42         mDoubleFactor = 2.0;
     43     }
     44 
     45     /**
     46      * Constructor
     47      *
     48      * @param factor Degree to which the animation should be eased. Seting
     49      *        factor to 1.0f produces a y=x^2 parabola. Increasing factor above
     50      *        1.0f  exaggerates the ease-in effect (i.e., it starts even
     51      *        slower and ends evens faster)
     52      */
     53     public AccelerateInterpolator(float factor) {
     54         mFactor = factor;
     55         mDoubleFactor = 2 * mFactor;
     56     }
     57 
     58     public AccelerateInterpolator(Context context, AttributeSet attrs) {
     59         this(context.getResources(), context.getTheme(), attrs);
     60     }
     61 
     62     /** @hide */
     63     public AccelerateInterpolator(Resources res, Theme theme, AttributeSet attrs) {
     64         TypedArray a;
     65         if (theme != null) {
     66             a = theme.obtainStyledAttributes(attrs, R.styleable.AccelerateInterpolator, 0, 0);
     67         } else {
     68             a = res.obtainAttributes(attrs, R.styleable.AccelerateInterpolator);
     69         }
     70 
     71         mFactor = a.getFloat(R.styleable.AccelerateInterpolator_factor, 1.0f);
     72         mDoubleFactor = 2 * mFactor;
     73         setChangingConfiguration(a.getChangingConfigurations());
     74         a.recycle();
     75     }
     76 
     77     public float getInterpolation(float input) {
     78         if (mFactor == 1.0f) {
     79             return input * input;
     80         } else {
     81             return (float)Math.pow(input, mDoubleFactor);
     82         }
     83     }
     84 
     85     /** @hide */
     86     @Override
     87     public long createNativeInterpolator() {
     88         return NativeInterpolatorFactoryHelper.createAccelerateInterpolator(mFactor);
     89     }
     90 }
     91