AccelerateInterpolator.java revision 54b6cfa9a9e5b861a9930af873580d6dc20f773c 
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    public AccelerateInterpolator() {
30    }
31
32    /**
33     * Constructor
34     *
35     * @param factor Degree to which the animation should be eased. Seting
36     *        factor to 1.0f produces a y=x^2 parabola. Increasing factor above
37     *        1.0f  exaggerates the ease-in effect (i.e., it starts even
38     *        slower and ends evens faster)
39     */
40    public AccelerateInterpolator(float factor) {
41        mFactor = factor;
42    }
43
44    public AccelerateInterpolator(Context context, AttributeSet attrs) {
45        TypedArray a =
46            context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.AccelerateInterpolator);
47
48        mFactor = a.getFloat(com.android.internal.R.styleable.AccelerateInterpolator_factor, 1.0f);
49
50        a.recycle();
51    }
52
53    public float getInterpolation(float input) {
54        if (mFactor == 1.0f) {
55            return (float)(input * input);
56        } else {
57            return (float)Math.pow(input, 2 * mFactor);
58        }
59    }
60
61    private float mFactor = 1.0f;
62}
63