AnticipateOvershootInterpolator.java
/*
* Copyright 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.core.animation;
import android.content.Context;
import android.content.res.Resources;
import android.content.res.Resources.Theme;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import androidx.annotation.FloatRange;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
/**
* An interpolator where the change starts backward then flings forward and overshoots
* the target value and finally goes back to the final value.
*/
public class AnticipateOvershootInterpolator implements Interpolator {
private final float mTension;
/**
* Creates a new instance of {@link AnticipateOvershootInterpolator} with slight anticipate and
* overshoot.
*/
public AnticipateOvershootInterpolator() {
mTension = 2.0f * 1.5f;
}
/**
* Creates a new instance of {@link AnticipateOvershootInterpolator}.
*
* @param tension Amount of anticipation/overshoot. When tension equals 0.0f,
* there is no anticipation/overshoot and the interpolator becomes
* a simple acceleration/deceleration interpolator.
*/
public AnticipateOvershootInterpolator(float tension) {
mTension = tension * 1.5f;
}
/**
* Creates a new instance of {@link AnticipateOvershootInterpolator}.
*
* @param tension Amount of anticipation/overshoot. When tension equals 0.0f,
* there is no anticipation/overshoot and the interpolator becomes
* a simple acceleration/deceleration interpolator.
* @param extraTension Amount by which to multiply the tension. For instance,
* to get the same overshoot as an OvershootInterpolator with
* a tension of 2.0f, you would use an extraTension of 1.5f.
*/
public AnticipateOvershootInterpolator(float tension, float extraTension) {
mTension = tension * extraTension;
}
public AnticipateOvershootInterpolator(@NonNull Context context, @Nullable AttributeSet attrs) {
this(context.getResources(), context.getTheme(), attrs);
}
AnticipateOvershootInterpolator(Resources res, Theme theme, AttributeSet attrs) {
TypedArray a;
if (theme != null) {
a = theme.obtainStyledAttributes(attrs,
AndroidResources.STYLEABLE_ANTICIPATEOVERSHOOT_INTERPOLATOR, 0, 0);
} else {
a = res.obtainAttributes(attrs,
AndroidResources.STYLEABLE_ANTICIPATEOVERSHOOT_INTERPOLATOR);
}
mTension = a.getFloat(AndroidResources.STYLEABLE_ANTICIPATEOVERSHOOT_INTERPOLATOR_TENSION,
2.0f) * a.getFloat(
AndroidResources.STYLEABLE_ANTICIPATEOVERSHOOT_INTERPOLATOR_EXTRA_TENSION,
1.5f);
a.recycle();
}
private static float a(float t, float s) {
return t * t * ((s + 1) * t - s);
}
private static float o(float t, float s) {
return t * t * ((s + 1) * t + s);
}
@Override
@FloatRange(to = 1)
public float getInterpolation(@FloatRange(from = 0, to = 1) float t) {
// a(t, s) = t * t * ((s + 1) * t - s)
// o(t, s) = t * t * ((s + 1) * t + s)
// f(t) = 0.5 * a(t * 2, tension * extraTension), when t < 0.5
// f(t) = 0.5 * (o(t * 2 - 2, tension * extraTension) + 2), when t <= 1.0
if (t < 0.5f) return 0.5f * a(t * 2.0f, mTension);
else return 0.5f * (o(t * 2.0f - 2.0f, mTension) + 2.0f);
}
}