AnticipateInterpolator.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.
*/
public class AnticipateInterpolator implements Interpolator {
private final float mTension;
/**
* Creates a new instance of {@link AnticipateInterpolator}.
*/
public AnticipateInterpolator() {
mTension = 2.0f;
}
/**
* Creates a new instance of {@link AnticipateInterpolator}.
*
* @param tension Amount of anticipation. When tension equals 0.0f, there is
* no anticipation and the interpolator becomes a simple
* acceleration interpolator.
*/
public AnticipateInterpolator(float tension) {
mTension = tension;
}
/**
* Creates a new instance of {@link AnticipateInterpolator} from XML.
*
* @param context The context.
* @param attrs The {@link AttributeSet} from the XML.
*/
public AnticipateInterpolator(@NonNull Context context, @Nullable AttributeSet attrs) {
this(context.getResources(), context.getTheme(), attrs);
}
AnticipateInterpolator(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.recycle();
}
@Override
@FloatRange(to = 1)
public float getInterpolation(@FloatRange(from = 0, to = 1) float t) {
// a(t) = t * t * ((tension + 1) * t - tension)
return t * t * ((mTension + 1) * t - mTension);
}
}