1/*
2 * Copyright (C) 2014 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 com.android.internal.view.animation;
18
19import android.animation.TimeInterpolator;
20import android.util.TimeUtils;
21import android.view.Choreographer;
22
23/**
24 * Interpolator that builds a lookup table to use. This is a fallback for
25 * building a native interpolator from a TimeInterpolator that is not marked
26 * with {@link HasNativeInterpolator}
27 *
28 * This implements TimeInterpolator to allow for easier interop with Animators
29 */
30@HasNativeInterpolator
31public class FallbackLUTInterpolator implements NativeInterpolatorFactory, TimeInterpolator {
32
33    // If the duration of an animation is more than 300 frames, we cap the sample size to 300.
34    private static final int MAX_SAMPLE_POINTS = 300;
35    private TimeInterpolator mSourceInterpolator;
36    private final float mLut[];
37
38    /**
39     * Used to cache the float[] LUT for use across multiple native
40     * interpolator creation
41     */
42    public FallbackLUTInterpolator(TimeInterpolator interpolator, long duration) {
43        mSourceInterpolator = interpolator;
44        mLut = createLUT(interpolator, duration);
45    }
46
47    private static float[] createLUT(TimeInterpolator interpolator, long duration) {
48        long frameIntervalNanos = Choreographer.getInstance().getFrameIntervalNanos();
49        int animIntervalMs = (int) (frameIntervalNanos / TimeUtils.NANOS_PER_MS);
50        // We need 2 frame values as the minimal.
51        int numAnimFrames = Math.max(2, (int) Math.ceil(((double) duration) / animIntervalMs));
52        numAnimFrames = Math.min(numAnimFrames, MAX_SAMPLE_POINTS);
53        float values[] = new float[numAnimFrames];
54        float lastFrame = numAnimFrames - 1;
55        for (int i = 0; i < numAnimFrames; i++) {
56            float inValue = i / lastFrame;
57            values[i] = interpolator.getInterpolation(inValue);
58        }
59        return values;
60    }
61
62    @Override
63    public long createNativeInterpolator() {
64        return NativeInterpolatorFactoryHelper.createLutInterpolator(mLut);
65    }
66
67    /**
68     * Used to create a one-shot float[] LUT & native interpolator
69     */
70    public static long createNativeInterpolator(TimeInterpolator interpolator, long duration) {
71        float[] lut = createLUT(interpolator, duration);
72        return NativeInterpolatorFactoryHelper.createLutInterpolator(lut);
73    }
74
75    @Override
76    public float getInterpolation(float input) {
77        return mSourceInterpolator.getInterpolation(input);
78    }
79}
80