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/*
* Copyright (C) 2016 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.launcher3.util;
import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ValueAnimator;
import android.animation.ValueAnimator.AnimatorUpdateListener;
import android.content.Context;
import android.view.View;
import android.view.accessibility.AccessibilityManager;
import java.util.Arrays;
/**
* A utility class which divides the alpha for a view across multiple states.
*/
public class MultiStateAlphaController {
private final View mTargetView;
private final float[] mAlphas;
private final AccessibilityManager mAm;
private int mZeroAlphaListenerCount = 0;
public MultiStateAlphaController(View view, int stateCount) {
mTargetView = view;
mAlphas = new float[stateCount];
Arrays.fill(mAlphas, 1);
mAm = (AccessibilityManager) view.getContext().getSystemService(Context.ACCESSIBILITY_SERVICE);
}
public void setAlphaAtIndex(float alpha, int index) {
mAlphas[index] = alpha;
updateAlpha();
}
private void updateAlpha() {
// Only update the alpha if no zero-alpha animation is running.
if (mZeroAlphaListenerCount > 0) {
return;
}
float finalAlpha = 1;
for (float a : mAlphas) {
finalAlpha = finalAlpha * a;
}
mTargetView.setAlpha(finalAlpha);
mTargetView.setVisibility(finalAlpha > 0 ? View.VISIBLE
: (mAm.isEnabled() ? View.GONE : View.INVISIBLE));
}
/**
* Returns an animator which changes the alpha at the index {@param index}
* to {@param finalAlpha}. Alphas at other index are not affected.
*/
public Animator animateAlphaAtIndex(float finalAlpha, final int index) {
final ValueAnimator anim;
if (Float.compare(finalAlpha, mAlphas[index]) == 0) {
// Return a dummy animator to avoid null checks.
anim = ValueAnimator.ofFloat(0, 0);
} else {
ValueAnimator animator = ValueAnimator.ofFloat(mAlphas[index], finalAlpha);
animator.addUpdateListener(new AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator valueAnimator) {
float value = (Float) valueAnimator.getAnimatedValue();
setAlphaAtIndex(value, index);
}
});
anim = animator;
}
if (Float.compare(finalAlpha, 0f) == 0) {
// In case when any channel is animating to 0, and the current alpha is also 0, do not
// update alpha of the target view while the animation is running.
// We special case '0' because if any channel is set to 0, values of other
// channels do not matter.
anim.addListener(new ZeroAlphaAnimatorListener());
}
return anim;
}
private class ZeroAlphaAnimatorListener extends AnimatorListenerAdapter {
private boolean mStartedAtZero = false;
@Override
public void onAnimationStart(Animator animation) {
mStartedAtZero = Float.compare(mTargetView.getAlpha(), 0f) == 0;
if (mStartedAtZero) {
mZeroAlphaListenerCount++;
mTargetView.setAlpha(0);
}
}
@Override
public void onAnimationEnd(Animator animation) {
if (mStartedAtZero) {
mZeroAlphaListenerCount--;
updateAlpha();
}
}
}
}
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