OvershootInterpolator.java revision 843ef36f7b96cc19ea7d2996b7c8661b41ec3452 
1/*
2 * Copyright (C) 2009 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 change flings forward and overshoots the last value
25 * then comes back.
26 */
27public class OvershootInterpolator implements Interpolator {
28    private final float mTension;
29
30    public OvershootInterpolator() {
31        mTension = 2.0f;
32    }
33
34    /**
35     * @param tension Amount of overshoot. When tension equals 0.0f, there is
36     *                no overshoot and the interpolator becomes a simple
37     *                deceleration interpolator.
38     */
39    public OvershootInterpolator(float tension) {
40        mTension = tension;
41    }
42
43    public OvershootInterpolator(Context context, AttributeSet attrs) {
44        TypedArray a = context.obtainStyledAttributes(attrs,
45                com.android.internal.R.styleable.OvershootInterpolator);
46
47        mTension =
48                a.getFloat(com.android.internal.R.styleable.OvershootInterpolator_tension, 2.0f);
49
50        a.recycle();
51    }
52
53    public float getInterpolation(float t) {
54        // _o(t) = t * t * ((tension + 1) * t + tension)
55        // o(t) = _o(t - 1) + 1
56        t -= 1.0f;
57        return t * t * ((mTension + 1) * t + mTension) + 1.0f;
58    }
59}
60