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/*
* Copyright (C) 2010 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 android.animation;
import java.util.ArrayList;
import android.view.animation.Interpolator;
/**
* This class holds a collection of Keyframe objects and is called by Animator 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.
*/
class KeyframeSet {
private int mNumKeyframes;
ArrayList<Keyframe> mKeyframes;
public KeyframeSet(Keyframe... keyframes) {
mKeyframes = new ArrayList<Keyframe>();
for (Keyframe keyframe : keyframes) {
mKeyframes.add(keyframe);
}
mNumKeyframes = mKeyframes.size();
}
/**
* Gets the animated value, given the elapsed fraction of the animation (interpolated by the
* animation's interpolator) and the evaluator used to calculate in-between values. This
* function maps the input fraction to the appropriate keyframe interval and a fraction
* between them and returns the interpolated value. Note that the input fraction may fall
* outside the [0-1] bounds, if the animation's interpolator made that happen (e.g., a
* spring interpolation that might send the fraction past 1.0). We handle this situation by
* just using the two keyframes at the appropriate end when the value is outside those bounds.
*
* @param fraction The elapsed fraction of the animation
* @param evaluator The type evaluator to use when calculating the interpolated values.
* @return The animated value.
*/
public Object getValue(float fraction, TypeEvaluator evaluator) {
// TODO: special-case 2-keyframe common case
if (fraction <= 0f) {
final Keyframe prevKeyframe = mKeyframes.get(0);
final Keyframe nextKeyframe = mKeyframes.get(1);
final Interpolator interpolator = nextKeyframe.getInterpolator();
if (interpolator != null) {
fraction = interpolator.getInterpolation(fraction);
}
float intervalFraction = (fraction - prevKeyframe.getFraction()) /
(nextKeyframe.getFraction() - prevKeyframe.getFraction());
return evaluator.evaluate(intervalFraction, prevKeyframe.getValue(),
nextKeyframe.getValue());
} else if (fraction >= 1f) {
final Keyframe prevKeyframe = mKeyframes.get(mNumKeyframes - 2);
final Keyframe nextKeyframe = mKeyframes.get(mNumKeyframes - 1);
final Interpolator interpolator = nextKeyframe.getInterpolator();
if (interpolator != null) {
fraction = interpolator.getInterpolation(fraction);
}
float intervalFraction = (fraction - prevKeyframe.getFraction()) /
(nextKeyframe.getFraction() - prevKeyframe.getFraction());
return evaluator.evaluate(intervalFraction, prevKeyframe.getValue(),
nextKeyframe.getValue());
}
Keyframe prevKeyframe = mKeyframes.get(0);
for (int i = 1; i < mNumKeyframes; ++i) {
Keyframe nextKeyframe = mKeyframes.get(i);
if (fraction < nextKeyframe.getFraction()) {
final Interpolator interpolator = nextKeyframe.getInterpolator();
if (interpolator != null) {
fraction = interpolator.getInterpolation(fraction);
}
float intervalFraction = (fraction - prevKeyframe.getFraction()) /
(nextKeyframe.getFraction() - prevKeyframe.getFraction());
return evaluator.evaluate(intervalFraction, prevKeyframe.getValue(),
nextKeyframe.getValue());
}
prevKeyframe = nextKeyframe;
}
// shouldn't get here
return mKeyframes.get(mNumKeyframes - 1).getValue();
}
}
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