StopLogic.java
/*
* Copyright (C) 2018 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 androidx.constraintlayout.motion.utils;
import androidx.constraintlayout.core.motion.utils.SpringStopEngine;
import androidx.constraintlayout.core.motion.utils.StopEngine;
import androidx.constraintlayout.core.motion.utils.StopLogicEngine;
import androidx.constraintlayout.motion.widget.MotionInterpolator;
/**
* This contains the class to provide the logic for an animation to come to a stop.
* The setup defines a series of velocity gradients that gets to the desired position
* ending at 0 velocity.
* The path is computed such that the velocities are continuous
*
*
*/
public class StopLogic extends MotionInterpolator {
private StopLogicEngine mStopLogicEngine = new StopLogicEngine();
private SpringStopEngine mSpringStopEngine;
private StopEngine mEngine = mStopLogicEngine;
/**
* Debugging logic to log the state.
*
* @param desc Description to pre append
* @param time Time during animation
* @return string useful for debugging the state of the StopLogic
*/
public String debug(String desc, float time) {
return mEngine.debug(desc, time);
}
/**
* Get the velocity at a point in time
* @param x
* @return
*/
public float getVelocity(float x) {
return mEngine.getVelocity(x);
}
/**
* Configure the stop logic base on the parameters
* @param currentPos start position
* @param destination the ending position
* @param currentVelocity the starting velocity
* @param maxTime The maximum time to take
* @param maxAcceleration the maximum acceleration to use
* @param maxVelocity the maximum velocity to use
*/
public void config(float currentPos, float destination, float currentVelocity,
float maxTime, float maxAcceleration, float maxVelocity) {
mEngine = mStopLogicEngine;
mStopLogicEngine.config(currentPos, destination, currentVelocity,
maxTime, maxAcceleration, maxVelocity);
}
/**
* This configure the stop logic to be a spring.
* Moving from currentPosition(P0)
* to destination with an initial velocity of currentVelocity (V0)
* moving as if it has a mass (m) with spring constant stiffness(k), and friction(c)
* It moves with the equation acceleration a = (-k.x-c.v)/m.
* x = current position - destination
* v is velocity
*
* @param currentPos The current position
* @param destination The destination position
* @param currentVelocity the initial velocity
* @param mass the mass
* @param stiffness the stiffness or spring constant (the force by which the spring pulls)
* @param damping the stiffness or spring constant. (the resistance to the motion)
* @param stopThreshold (When the max velocity of the movement is below this it stops)
* @param boundaryMode This controls if it overshoots or bounces when it hits 0 and 1
*/
public void springConfig(float currentPos, float destination, float currentVelocity,
float mass, float stiffness, float damping, float stopThreshold,
int boundaryMode) {
if (mSpringStopEngine == null) {
mSpringStopEngine = new SpringStopEngine();
}
mEngine = mSpringStopEngine;
mSpringStopEngine.springConfig(currentPos, destination, currentVelocity, mass, stiffness,
damping, stopThreshold, boundaryMode);
}
@Override
public float getInterpolation(float v) {
return mEngine.getInterpolation(v);
}
@Override
public float getVelocity() {
return mEngine.getVelocity();
}
public boolean isStopped() {
return mEngine.isStopped();
}
}