DecelerateInterpolator.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.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 rate of change starts out quickly and
* and then decelerates.
*
*/
public class DecelerateInterpolator implements Interpolator {
public DecelerateInterpolator() {
}
/**
* Constructor
*
* @param factor Degree to which the animation should be eased. Setting factor to 1.0f produces
* an upside-down y=x^2 parabola. Increasing factor above 1.0f makes exaggerates the
* ease-out effect (i.e., it starts even faster and ends evens slower)
*/
public DecelerateInterpolator(float factor) {
mFactor = factor;
}
public DecelerateInterpolator(@NonNull Context context, @Nullable AttributeSet attrs) {
this(context.getResources(), context.getTheme(), attrs);
}
DecelerateInterpolator(Resources res, Theme theme, AttributeSet attrs) {
TypedArray a;
if (theme != null) {
a = theme.obtainStyledAttributes(attrs,
AndroidResources.STYLEABLE_DECELERATE_INTERPOLATOR, 0, 0);
} else {
a = res.obtainAttributes(attrs, AndroidResources.STYLEABLE_DECELERATE_INTERPOLATOR);
}
mFactor = a.getFloat(AndroidResources.STYLEABLE_DECELERATE_INTERPOLATOR_FACTOR,
1.0f);
a.recycle();
}
@Override
@FloatRange(from = 0, to = 1)
public float getInterpolation(@FloatRange(from = 0, to = 1) float input) {
float result;
if (mFactor == 1.0f) {
result = 1.0f - (1.0f - input) * (1.0f - input);
} else {
result = (float) (1.0f - Math.pow((1.0f - input), 2 * mFactor));
}
return result;
}
private float mFactor = 1.0f;
}