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/*
* Copyright (C) 2012 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 com.android.server.power;
import android.animation.ValueAnimator;
import android.util.IntProperty;
import android.view.Choreographer;
/**
* A custom animator that progressively updates a property value at
* a given variable rate until it reaches a particular target value.
*/
final class RampAnimator<T> {
private final T mObject;
private final IntProperty<T> mProperty;
private final Choreographer mChoreographer;
private int mCurrentValue;
private int mTargetValue;
private int mRate;
private boolean mAnimating;
private float mAnimatedValue; // higher precision copy of mCurrentValue
private long mLastFrameTimeNanos;
private boolean mFirstTime = true;
public RampAnimator(T object, IntProperty<T> property) {
mObject = object;
mProperty = property;
mChoreographer = Choreographer.getInstance();
}
/**
* Starts animating towards the specified value.
*
* If this is the first time the property is being set, the value jumps
* directly to the target.
*
* @param target The target value.
* @param rate The convergence rate, in units per second.
* @return True if the target differs from the previous target.
*/
public boolean animateTo(int target, int rate) {
// Immediately jump to the target the first time.
if (mFirstTime) {
mFirstTime = false;
mProperty.setValue(mObject, target);
mCurrentValue = target;
return true;
}
// Adjust the rate based on the closest target.
// If a faster rate is specified, then use the new rate so that we converge
// more rapidly based on the new request.
// If a slower rate is specified, then use the new rate only if the current
// value is somewhere in between the new and the old target meaning that
// we will be ramping in a different direction to get there.
// Otherwise, continue at the previous rate.
if (!mAnimating
|| rate > mRate
|| (target <= mCurrentValue && mCurrentValue <= mTargetValue)
|| (mTargetValue <= mCurrentValue && mCurrentValue <= target)) {
mRate = rate;
}
final boolean changed = (mTargetValue != target);
mTargetValue = target;
// Start animating.
if (!mAnimating && target != mCurrentValue) {
mAnimating = true;
mAnimatedValue = mCurrentValue;
mLastFrameTimeNanos = System.nanoTime();
postCallback();
}
return changed;
}
private void postCallback() {
mChoreographer.postCallback(Choreographer.CALLBACK_ANIMATION, mCallback, null);
}
private final Runnable mCallback = new Runnable() {
@Override // Choreographer callback
public void run() {
final long frameTimeNanos = mChoreographer.getFrameTimeNanos();
final float timeDelta = (frameTimeNanos - mLastFrameTimeNanos)
* 0.000000001f;
mLastFrameTimeNanos = frameTimeNanos;
// Advance the animated value towards the target at the specified rate
// and clamp to the target. This gives us the new current value but
// we keep the animated value around to allow for fractional increments
// towards the target.
final float scale = ValueAnimator.getDurationScale();
if (scale == 0) {
// Animation off.
mAnimatedValue = mTargetValue;
} else {
final float amount = timeDelta * mRate / scale;
if (mTargetValue > mCurrentValue) {
mAnimatedValue = Math.min(mAnimatedValue + amount, mTargetValue);
} else {
mAnimatedValue = Math.max(mAnimatedValue - amount, mTargetValue);
}
}
final int oldCurrentValue = mCurrentValue;
mCurrentValue = Math.round(mAnimatedValue);
if (oldCurrentValue != mCurrentValue) {
mProperty.setValue(mObject, mCurrentValue);
}
if (mTargetValue != mCurrentValue) {
postCallback();
} else {
mAnimating = false;
}
}
};
}
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