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/*
* Copyright (C) 2013 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 com.example.android.curvedmotion;
import android.animation.TypeEvaluator;
/**
* This evaluator interpolates between two PathPoint values given the value t, the
* proportion traveled between those points. The value of the interpolation depends
* on the operation specified by the endValue (the operation for the interval between
* PathPoints is always specified by the end point of that interval).
*/
public class PathEvaluator implements TypeEvaluator<PathPoint> {
@Override
public PathPoint evaluate(float t, PathPoint startValue, PathPoint endValue) {
float x, y;
if (endValue.mOperation == PathPoint.CURVE) {
float oneMinusT = 1 - t;
x = oneMinusT * oneMinusT * oneMinusT * startValue.mX +
3 * oneMinusT * oneMinusT * t * endValue.mControl0X +
3 * oneMinusT * t * t * endValue.mControl1X +
t * t * t * endValue.mX;
y = oneMinusT * oneMinusT * oneMinusT * startValue.mY +
3 * oneMinusT * oneMinusT * t * endValue.mControl0Y +
3 * oneMinusT * t * t * endValue.mControl1Y +
t * t * t * endValue.mY;
} else if (endValue.mOperation == PathPoint.LINE) {
x = startValue.mX + t * (endValue.mX - startValue.mX);
y = startValue.mY + t * (endValue.mY - startValue.mY);
} else {
x = endValue.mX;
y = endValue.mY;
}
return PathPoint.moveTo(x, y);
}
}
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