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 
17 package com.android.internal.view.animation;
18 
19 import android.animation.TimeInterpolator;
20 import android.util.TimeUtils;
21 import 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
31 public 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      */
FallbackLUTInterpolator(TimeInterpolator interpolator, long duration)42     public FallbackLUTInterpolator(TimeInterpolator interpolator, long duration) {
43         mSourceInterpolator = interpolator;
44         mLut = createLUT(interpolator, duration);
45     }
46 
createLUT(TimeInterpolator interpolator, long duration)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
createNativeInterpolator()63     public long createNativeInterpolator() {
64         return NativeInterpolatorFactoryHelper.createLutInterpolator(mLut);
65     }
66 
67     /**
68      * Used to create a one-shot float[] LUT & native interpolator
69      */
createNativeInterpolator(TimeInterpolator interpolator, long duration)70     public static long createNativeInterpolator(TimeInterpolator interpolator, long duration) {
71         float[] lut = createLUT(interpolator, duration);
72         return NativeInterpolatorFactoryHelper.createLutInterpolator(lut);
73     }
74 
75     @Override
getInterpolation(float input)76     public float getInterpolation(float input) {
77         return mSourceInterpolator.getInterpolation(input);
78     }
79 }
80