84 lines
3.1 KiB
Java
84 lines
3.1 KiB
Java
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/*
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* Copyright (C) 2013 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.animation;
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import android.graphics.PointF;
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/**
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* This evaluator can be used to perform type interpolation between <code>PointF</code> values.
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*/
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public class PointFEvaluator implements TypeEvaluator<PointF> {
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/**
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* When null, a new PointF is returned on every evaluate call. When non-null,
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* mPoint will be modified and returned on every evaluate.
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*/
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private PointF mPoint;
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/**
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* Construct a PointFEvaluator that returns a new PointF on every evaluate call.
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* To avoid creating an object for each evaluate call,
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* {@link PointFEvaluator#PointFEvaluator(android.graphics.PointF)} should be used
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* whenever possible.
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*/
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public PointFEvaluator() {
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}
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/**
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* Constructs a PointFEvaluator that modifies and returns <code>reuse</code>
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* in {@link #evaluate(float, android.graphics.PointF, android.graphics.PointF)} calls.
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* The value returned from
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* {@link #evaluate(float, android.graphics.PointF, android.graphics.PointF)} should
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* not be cached because it will change over time as the object is reused on each
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* call.
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*
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* @param reuse A PointF to be modified and returned by evaluate.
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*/
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public PointFEvaluator(PointF reuse) {
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mPoint = reuse;
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}
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/**
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* This function returns the result of linearly interpolating the start and
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* end PointF values, with <code>fraction</code> representing the proportion
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* between the start and end values. The calculation is a simple parametric
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* calculation on each of the separate components in the PointF objects
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* (x, y).
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*
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* <p>If {@link #PointFEvaluator(android.graphics.PointF)} was used to construct
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* this PointFEvaluator, the object returned will be the <code>reuse</code>
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* passed into the constructor.</p>
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*
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* @param fraction The fraction from the starting to the ending values
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* @param startValue The start PointF
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* @param endValue The end PointF
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* @return A linear interpolation between the start and end values, given the
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* <code>fraction</code> parameter.
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*/
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@Override
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public PointF evaluate(float fraction, PointF startValue, PointF endValue) {
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float x = startValue.x + (fraction * (endValue.x - startValue.x));
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float y = startValue.y + (fraction * (endValue.y - startValue.y));
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if (mPoint != null) {
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mPoint.set(x, y);
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return mPoint;
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} else {
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return new PointF(x, y);
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}
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}
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}
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