core/core-animation/src/main/java/androidx/core/animation/FloatKeyframeSet.java

/*
 * Copyright 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package androidx.core.animation;

import androidx.annotation.NonNull;
import androidx.core.animation.Keyframe.FloatKeyframe;

import java.util.List;

/**
 * This class holds a collection of FloatKeyframe objects and is called by ValueAnimator to
 * calculate values between those keyframes for a given animation. The class internal to the
 * animation package because it is an implementation detail of how Keyframes are stored and used.
 *
 * <p>This type-specific subclass of KeyframeSet, along with the other type-specific subclass for
 * int, exists to speed up the getValue() method when there is no custom
 * TypeEvaluator set for the animation, so that values can be calculated without autoboxing to the
 * Object equivalents of these primitive types.</p>
 */
class FloatKeyframeSet extends KeyframeSet<Float> implements Keyframes.FloatKeyframes {
    FloatKeyframeSet(FloatKeyframe... keyframes) {
        super(keyframes);
    }

    @Override
    public Float getValue(float fraction) {
        return getFloatValue(fraction);
    }

    @NonNull
    @Override
    public FloatKeyframeSet clone() {
        final List<Keyframe<Float>> keyframes = mKeyframes;
        final int numKeyframes = mKeyframes.size();
        FloatKeyframe[] newKeyframes = new FloatKeyframe[numKeyframes];
        for (int i = 0; i < numKeyframes; ++i) {
            newKeyframes[i] = (FloatKeyframe) keyframes.get(i).clone();
        }
        FloatKeyframeSet newSet = new FloatKeyframeSet(newKeyframes);
        return newSet;
    }

    @Override
    public float getFloatValue(float fraction) {
        if (fraction <= 0f) {
            final FloatKeyframe prevKeyframe = (FloatKeyframe) mKeyframes.get(0);
            final FloatKeyframe nextKeyframe = (FloatKeyframe) mKeyframes.get(1);
            float prevValue = prevKeyframe.getFloatValue();
            float nextValue = nextKeyframe.getFloatValue();
            float prevFraction = prevKeyframe.getFraction();
            float nextFraction = nextKeyframe.getFraction();
            final Interpolator interpolator = nextKeyframe.getInterpolator();
            if (interpolator != null) {
                fraction = interpolator.getInterpolation(fraction);
            }
            float intervalFraction = (fraction - prevFraction) / (nextFraction - prevFraction);
            return mEvaluator == null ? prevValue + intervalFraction * (nextValue - prevValue)
                    : mEvaluator.evaluate(intervalFraction, prevValue, nextValue).floatValue();
        } else if (fraction >= 1f) {
            final FloatKeyframe prevKeyframe = (FloatKeyframe) mKeyframes.get(mNumKeyframes - 2);
            final FloatKeyframe nextKeyframe = (FloatKeyframe) mKeyframes.get(mNumKeyframes - 1);
            float prevValue = prevKeyframe.getFloatValue();
            float nextValue = nextKeyframe.getFloatValue();
            float prevFraction = prevKeyframe.getFraction();
            float nextFraction = nextKeyframe.getFraction();
            final Interpolator interpolator = nextKeyframe.getInterpolator();
            if (interpolator != null) {
                fraction = interpolator.getInterpolation(fraction);
            }
            float intervalFraction = (fraction - prevFraction) / (nextFraction - prevFraction);
            return mEvaluator == null ? prevValue + intervalFraction * (nextValue - prevValue)
                    : mEvaluator.evaluate(intervalFraction, prevValue, nextValue).floatValue();
        }
        FloatKeyframe prevKeyframe = (FloatKeyframe) mKeyframes.get(0);
        for (int i = 1; i < mNumKeyframes; ++i) {
            FloatKeyframe nextKeyframe = (FloatKeyframe) mKeyframes.get(i);
            if (fraction < nextKeyframe.getFraction()) {
                final Interpolator interpolator = nextKeyframe.getInterpolator();
                float intervalFraction = (fraction - prevKeyframe.getFraction())
                        / (nextKeyframe.getFraction() - prevKeyframe.getFraction());
                float prevValue = prevKeyframe.getFloatValue();
                float nextValue = nextKeyframe.getFloatValue();
                // Apply interpolator on the proportional duration.
                if (interpolator != null) {
                    intervalFraction = interpolator.getInterpolation(intervalFraction);
                }
                return mEvaluator == null ? prevValue + intervalFraction * (nextValue - prevValue)
                        : mEvaluator.evaluate(intervalFraction, prevValue, nextValue).floatValue();
            }
            prevKeyframe = nextKeyframe;
        }
        // shouldn't get here
        return mKeyframes.get(mNumKeyframes - 1).getValue().floatValue();
    }

    @Override
    public Class<Float> getType() {
        return Float.class;
    }
}