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
17package android.view.animation;
18
19import android.content.Context;
20import android.content.res.TypedArray;
21import android.util.AttributeSet;
22
23/**
24 * An interpolator where the rate of change starts out slowly and
25 * and then accelerates.
26 *
27 */
28public class AccelerateInterpolator implements Interpolator {
29    private final float mFactor;
30    private final double mDoubleFactor;
31
32    public AccelerateInterpolator() {
33        mFactor = 1.0f;
34        mDoubleFactor = 2.0;
35    }
36
37    /**
38     * Constructor
39     *
40     * @param factor Degree to which the animation should be eased. Seting
41     *        factor to 1.0f produces a y=x^2 parabola. Increasing factor above
42     *        1.0f  exaggerates the ease-in effect (i.e., it starts even
43     *        slower and ends evens faster)
44     */
45    public AccelerateInterpolator(float factor) {
46        mFactor = factor;
47        mDoubleFactor = 2 * mFactor;
48    }
49
50    public AccelerateInterpolator(Context context, AttributeSet attrs) {
51        TypedArray a =
52            context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.AccelerateInterpolator);
53
54        mFactor = a.getFloat(com.android.internal.R.styleable.AccelerateInterpolator_factor, 1.0f);
55        mDoubleFactor = 2 * mFactor;
56
57        a.recycle();
58    }
59
60    public float getInterpolation(float input) {
61        if (mFactor == 1.0f) {
62            return input * input;
63        } else {
64            return (float)Math.pow(input, mDoubleFactor);
65        }
66    }
67}
68