AnticipateOvershootInterpolator.java revision d422dc358f0100106dc07d7b903201eb9b043b11 
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.Resources;
21import android.content.res.Resources.Theme;
22import android.content.res.TypedArray;
23import android.util.AttributeSet;
24
25import com.android.internal.view.animation.HasNativeInterpolator;
26import com.android.internal.view.animation.NativeInterpolatorFactory;
27import com.android.internal.view.animation.NativeInterpolatorFactoryHelper;
28
29import static com.android.internal.R.styleable.AnticipateOvershootInterpolator_extraTension;
30import static com.android.internal.R.styleable.AnticipateOvershootInterpolator_tension;
31import static com.android.internal.R.styleable.AnticipateOvershootInterpolator;
32
33/**
34 * An interpolator where the change starts backward then flings forward and overshoots
35 * the target value and finally goes back to the final value.
36 */
37@HasNativeInterpolator
38public class AnticipateOvershootInterpolator extends BaseInterpolator
39        implements NativeInterpolatorFactory {
40    private final float mTension;
41
42    public AnticipateOvershootInterpolator() {
43        mTension = 2.0f * 1.5f;
44    }
45
46    /**
47     * @param tension Amount of anticipation/overshoot. When tension equals 0.0f,
48     *                there is no anticipation/overshoot and the interpolator becomes
49     *                a simple acceleration/deceleration interpolator.
50     */
51    public AnticipateOvershootInterpolator(float tension) {
52        mTension = tension * 1.5f;
53    }
54
55    /**
56     * @param tension Amount of anticipation/overshoot. When tension equals 0.0f,
57     *                there is no anticipation/overshoot and the interpolator becomes
58     *                a simple acceleration/deceleration interpolator.
59     * @param extraTension Amount by which to multiply the tension. For instance,
60     *                     to get the same overshoot as an OvershootInterpolator with
61     *                     a tension of 2.0f, you would use an extraTension of 1.5f.
62     */
63    public AnticipateOvershootInterpolator(float tension, float extraTension) {
64        mTension = tension * extraTension;
65    }
66
67    public AnticipateOvershootInterpolator(Context context, AttributeSet attrs) {
68        this(context.getResources(), context.getTheme(), attrs);
69    }
70
71    /** @hide */
72    public AnticipateOvershootInterpolator(Resources res, Theme theme, AttributeSet attrs) {
73        TypedArray a;
74        if (theme != null) {
75            a = theme.obtainStyledAttributes(attrs, AnticipateOvershootInterpolator, 0, 0);
76        } else {
77            a = res.obtainAttributes(attrs, AnticipateOvershootInterpolator);
78        }
79
80        mTension = a.getFloat(AnticipateOvershootInterpolator_tension, 2.0f) *
81                a.getFloat(AnticipateOvershootInterpolator_extraTension, 1.5f);
82        setChangingConfiguration(a.getChangingConfigurations());
83        a.recycle();
84    }
85
86    private static float a(float t, float s) {
87        return t * t * ((s + 1) * t - s);
88    }
89
90    private static float o(float t, float s) {
91        return t * t * ((s + 1) * t + s);
92    }
93
94    public float getInterpolation(float t) {
95        // a(t, s) = t * t * ((s + 1) * t - s)
96        // o(t, s) = t * t * ((s + 1) * t + s)
97        // f(t) = 0.5 * a(t * 2, tension * extraTension), when t < 0.5
98        // f(t) = 0.5 * (o(t * 2 - 2, tension * extraTension) + 2), when t <= 1.0
99        if (t < 0.5f) return 0.5f * a(t * 2.0f, mTension);
100        else return 0.5f * (o(t * 2.0f - 2.0f, mTension) + 2.0f);
101    }
102
103    /** @hide */
104    @Override
105    public long createNativeInterpolator() {
106        return NativeInterpolatorFactoryHelper.createAnticipateOvershootInterpolator(mTension);
107    }
108}
109