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      1 /*
      2  * Copyright (C) 2018 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.launcher3.util;
     18 
     19 import android.util.Property;
     20 import android.view.View;
     21 
     22 /**
     23  * Utility class to handle separating a single value as a factor of multiple values
     24  */
     25 public class MultiValueAlpha {
     26 
     27     public static final Property<AlphaProperty, Float> VALUE =
     28             new Property<AlphaProperty, Float>(Float.TYPE, "value") {
     29 
     30                 @Override
     31                 public Float get(AlphaProperty alphaProperty) {
     32                     return alphaProperty.mValue;
     33                 }
     34 
     35                 @Override
     36                 public void set(AlphaProperty object, Float value) {
     37                     object.setValue(value);
     38                 }
     39             };
     40 
     41     private final View mView;
     42     private final AlphaProperty[] mMyProperties;
     43 
     44     private int mValidMask;
     45 
     46     public MultiValueAlpha(View view, int size) {
     47         mView = view;
     48         mMyProperties = new AlphaProperty[size];
     49 
     50         mValidMask = 0;
     51         for (int i = 0; i < size; i++) {
     52             int myMask = 1 << i;
     53             mValidMask |= myMask;
     54             mMyProperties[i] = new AlphaProperty(myMask);
     55         }
     56     }
     57 
     58     public AlphaProperty getProperty(int index) {
     59         return mMyProperties[index];
     60     }
     61 
     62     public class AlphaProperty {
     63 
     64         private final int mMyMask;
     65 
     66         private float mValue = 1;
     67         // Factor of all other alpha channels, only valid if mMyMask is present in mValidMask.
     68         private float mOthers = 1;
     69 
     70         AlphaProperty(int myMask) {
     71             mMyMask = myMask;
     72         }
     73 
     74         public void setValue(float value) {
     75             if (mValue == value) {
     76                 return;
     77             }
     78 
     79             if ((mValidMask & mMyMask) == 0) {
     80                 // Our cache value is not correct, recompute it.
     81                 mOthers = 1;
     82                 for (AlphaProperty prop : mMyProperties) {
     83                     if (prop != this) {
     84                         mOthers *= prop.mValue;
     85                     }
     86                 }
     87             }
     88 
     89             // Since we have changed our value, all other caches except our own need to be
     90             // recomputed. Change mValidMask to indicate the new valid caches (only our own).
     91             mValidMask = mMyMask;
     92             mValue = value;
     93 
     94             mView.setAlpha(mOthers * mValue);
     95         }
     96 
     97         public float getValue() {
     98             return mValue;
     99         }
    100     }
    101 }
    102