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 android.graphics.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  * @hide
30  */
31 @HasNativeInterpolator
32 public class FallbackLUTInterpolator implements NativeInterpolator, TimeInterpolator {
33 
34     // If the duration of an animation is more than 300 frames, we cap the sample size to 300.
35     private static final int MAX_SAMPLE_POINTS = 300;
36     private TimeInterpolator mSourceInterpolator;
37     private final float[] mLut;
38 
39     /**
40      * Used to cache the float[] LUT for use across multiple native
41      * interpolator creation
42      */
FallbackLUTInterpolator(TimeInterpolator interpolator, long duration)43     public FallbackLUTInterpolator(TimeInterpolator interpolator, long duration) {
44         mSourceInterpolator = interpolator;
45         mLut = createLUT(interpolator, duration);
46     }
47 
createLUT(TimeInterpolator interpolator, long duration)48     private static float[] createLUT(TimeInterpolator interpolator, long duration) {
49         long frameIntervalNanos = Choreographer.getInstance().getFrameIntervalNanos();
50         int animIntervalMs = (int) (frameIntervalNanos / TimeUtils.NANOS_PER_MS);
51         // We need 2 frame values as the minimal.
52         int numAnimFrames = Math.max(2, (int) Math.ceil(((double) duration) / animIntervalMs));
53         numAnimFrames = Math.min(numAnimFrames, MAX_SAMPLE_POINTS);
54         float[] values = new float[numAnimFrames];
55         float lastFrame = numAnimFrames - 1;
56         for (int i = 0; i < numAnimFrames; i++) {
57             float inValue = i / lastFrame;
58             values[i] = interpolator.getInterpolation(inValue);
59         }
60         return values;
61     }
62 
63     @Override
createNativeInterpolator()64     public long createNativeInterpolator() {
65         return NativeInterpolatorFactory.createLutInterpolator(mLut);
66     }
67 
68     /**
69      * Used to create a one-shot float[] LUT & native interpolator
70      */
createNativeInterpolator(TimeInterpolator interpolator, long duration)71     public static long createNativeInterpolator(TimeInterpolator interpolator, long duration) {
72         float[] lut = createLUT(interpolator, duration);
73         return NativeInterpolatorFactory.createLutInterpolator(lut);
74     }
75 
76     @Override
getInterpolation(float input)77     public float getInterpolation(float input) {
78         return mSourceInterpolator.getInterpolation(input);
79     }
80 }
81