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.Resources;
21import android.content.res.Resources.Theme;
22import android.content.res.TypedArray;
23import android.util.AttributeSet;
24
25import com.android.internal.R;
26import com.android.internal.view.animation.HasNativeInterpolator;
27import com.android.internal.view.animation.NativeInterpolatorFactory;
28import com.android.internal.view.animation.NativeInterpolatorFactoryHelper;
29
30/**
31 * An interpolator where the rate of change starts out slowly and
32 * and then accelerates.
33 *
34 */
35@HasNativeInterpolator
36public class AccelerateInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
37    private final float mFactor;
38    private final double mDoubleFactor;
39
40    public AccelerateInterpolator() {
41        mFactor = 1.0f;
42        mDoubleFactor = 2.0;
43    }
44
45    /**
46     * Constructor
47     *
48     * @param factor Degree to which the animation should be eased. Seting
49     *        factor to 1.0f produces a y=x^2 parabola. Increasing factor above
50     *        1.0f  exaggerates the ease-in effect (i.e., it starts even
51     *        slower and ends evens faster)
52     */
53    public AccelerateInterpolator(float factor) {
54        mFactor = factor;
55        mDoubleFactor = 2 * mFactor;
56    }
57
58    public AccelerateInterpolator(Context context, AttributeSet attrs) {
59        this(context.getResources(), context.getTheme(), attrs);
60    }
61
62    /** @hide */
63    public AccelerateInterpolator(Resources res, Theme theme, AttributeSet attrs) {
64        TypedArray a;
65        if (theme != null) {
66            a = theme.obtainStyledAttributes(attrs, R.styleable.AccelerateInterpolator, 0, 0);
67        } else {
68            a = res.obtainAttributes(attrs, R.styleable.AccelerateInterpolator);
69        }
70
71        mFactor = a.getFloat(R.styleable.AccelerateInterpolator_factor, 1.0f);
72        mDoubleFactor = 2 * mFactor;
73        setChangingConfiguration(a.getChangingConfigurations());
74        a.recycle();
75    }
76
77    public float getInterpolation(float input) {
78        if (mFactor == 1.0f) {
79            return input * input;
80        } else {
81            return (float)Math.pow(input, mDoubleFactor);
82        }
83    }
84
85    /** @hide */
86    @Override
87    public long createNativeInterpolator() {
88        return NativeInterpolatorFactoryHelper.createAccelerateInterpolator(mFactor);
89    }
90}
91