DecelerateInterpolator.java revision 9066cfe9886ac131c34d59ed0e2d287b0e3c0087 
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
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 quickly and
25 * and then decelerates.
26 *
27 */
28public class DecelerateInterpolator implements Interpolator {
29    public DecelerateInterpolator() {
30    }
31
32    /**
33     * Constructor
34     *
35     * @param factor Degree to which the animation should be eased. Seting factor to 1.0f produces
36     *        an upside-down y=x^2 parabola. Increasing factor above 1.0f makes exaggerates the
37     *        ease-out effect (i.e., it starts even faster and ends evens slower)
38     */
39    public DecelerateInterpolator(float factor) {
40        mFactor = factor;
41    }
42
43    public DecelerateInterpolator(Context context, AttributeSet attrs) {
44        TypedArray a =
45            context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.DecelerateInterpolator);
46
47        mFactor = a.getFloat(com.android.internal.R.styleable.DecelerateInterpolator_factor, 1.0f);
48
49        a.recycle();
50    }
51
52    public float getInterpolation(float input) {
53        if (mFactor == 1.0f) {
54            return (float)(1.0f - (1.0f - input) * (1.0f - input));
55        } else {
56            return (float)(1.0f - Math.pow((1.0f - input), 2 * mFactor));
57        }
58    }
59
60    private float mFactor = 1.0f;
61}
62