/*
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* Copyright (C) 2019 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 com.android.launcher3.anim;
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import androidx.dynamicanimation.animation.DynamicAnimation.OnAnimationEndListener;
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import androidx.dynamicanimation.animation.FlingAnimation;
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import androidx.dynamicanimation.animation.FloatPropertyCompat;
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import androidx.dynamicanimation.animation.SpringAnimation;
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import androidx.dynamicanimation.animation.SpringForce;
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/**
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* Given a property to animate and a target value and starting velocity, first apply friction to
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* the fling until we pass the target, then apply a spring force to pull towards the target.
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*/
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public class FlingSpringAnim {
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private static final float FLING_FRICTION = 1.5f;
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private static final float SPRING_STIFFNESS = 200;
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private static final float SPRING_DAMPING = 0.8f;
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private final FlingAnimation mFlingAnim;
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private SpringAnimation mSpringAnim;
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private float mTargetPosition;
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public <K> FlingSpringAnim(K object, FloatPropertyCompat<K> property, float startPosition,
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float targetPosition, float startVelocity, float minVisChange, float minValue,
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float maxValue, float springVelocityFactor, OnAnimationEndListener onEndListener) {
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mFlingAnim = new FlingAnimation(object, property)
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.setFriction(FLING_FRICTION)
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// Have the spring pull towards the target if we've slowed down too much before
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// reaching it.
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.setMinimumVisibleChange(minVisChange)
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.setStartVelocity(startVelocity)
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.setMinValue(minValue)
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.setMaxValue(maxValue);
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mTargetPosition = targetPosition;
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mFlingAnim.addEndListener(((animation, canceled, value, velocity) -> {
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mSpringAnim = new SpringAnimation(object, property)
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.setStartValue(value)
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.setStartVelocity(velocity * springVelocityFactor)
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.setSpring(new SpringForce(mTargetPosition)
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.setStiffness(SPRING_STIFFNESS)
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.setDampingRatio(SPRING_DAMPING));
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mSpringAnim.addEndListener(onEndListener);
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mSpringAnim.animateToFinalPosition(mTargetPosition);
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}));
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}
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public float getTargetPosition() {
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return mTargetPosition;
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}
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public void updatePosition(float startPosition, float targetPosition) {
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mFlingAnim.setMinValue(Math.min(startPosition, targetPosition))
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.setMaxValue(Math.max(startPosition, targetPosition));
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mTargetPosition = targetPosition;
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if (mSpringAnim != null) {
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mSpringAnim.animateToFinalPosition(mTargetPosition);
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}
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}
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public void start() {
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mFlingAnim.start();
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}
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public void end() {
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mFlingAnim.cancel();
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if (mSpringAnim.canSkipToEnd()) {
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mSpringAnim.skipToEnd();
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}
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}
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}
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