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/*
* Copyright (C) 2009 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 android.view.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 com.android.internal.view.animation.HasNativeInterpolator;
import com.android.internal.view.animation.NativeInterpolatorFactory;
import com.android.internal.view.animation.NativeInterpolatorFactoryHelper;
import static com.android.internal.R.styleable.AnticipateOvershootInterpolator_extraTension;
import static com.android.internal.R.styleable.AnticipateOvershootInterpolator_tension;
import static com.android.internal.R.styleable.AnticipateOvershootInterpolator;
/**
* An interpolator where the change starts backward then flings forward and overshoots
* the target value and finally goes back to the final value.
*/
@HasNativeInterpolator
public class AnticipateOvershootInterpolator extends BaseInterpolator
implements NativeInterpolatorFactory {
private final float mTension;
public AnticipateOvershootInterpolator() {
mTension = 2.0f * 1.5f;
}
/**
* @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;
}
/**
* @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(Context context, AttributeSet attrs) {
this(context.getResources(), context.getTheme(), attrs);
}
/** @hide */
public AnticipateOvershootInterpolator(Resources res, Theme theme, AttributeSet attrs) {
TypedArray a;
if (theme != null) {
a = theme.obtainStyledAttributes(attrs, AnticipateOvershootInterpolator, 0, 0);
} else {
a = res.obtainAttributes(attrs, AnticipateOvershootInterpolator);
}
mTension = a.getFloat(AnticipateOvershootInterpolator_tension, 2.0f) *
a.getFloat(AnticipateOvershootInterpolator_extraTension, 1.5f);
setChangingConfiguration(a.getChangingConfigurations());
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);
}
public float getInterpolation(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);
}
/** @hide */
@Override
public long createNativeInterpolator() {
return NativeInterpolatorFactoryHelper.createAnticipateOvershootInterpolator(mTension);
}
}
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