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