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      1 /*
      2  * Copyright (C) 2014 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.systemui.recents.views;
     18 
     19 import android.content.Context;
     20 
     21 import java.util.Iterator;
     22 import java.util.LinkedList;
     23 import java.util.List;
     24 
     25 
     26 /* A view pool to manage more views than we can visibly handle */
     27 public class ViewPool<V, T> {
     28 
     29     /* An interface to the consumer of a view pool */
     30     public interface ViewPoolConsumer<V, T> {
     31         public V createView(Context context);
     32         public void onReturnViewToPool(V v);
     33         public void onPickUpViewFromPool(V v, T prepareData, boolean isNewView);
     34         public boolean hasPreferredData(V v, T preferredData);
     35     }
     36 
     37     Context mContext;
     38     ViewPoolConsumer<V, T> mViewCreator;
     39     LinkedList<V> mPool = new LinkedList<V>();
     40 
     41     /** Initializes the pool with a fixed predetermined pool size */
     42     public ViewPool(Context context, ViewPoolConsumer<V, T> viewCreator) {
     43         mContext = context;
     44         mViewCreator = viewCreator;
     45     }
     46 
     47     /** Returns a view into the pool */
     48     void returnViewToPool(V v) {
     49         mViewCreator.onReturnViewToPool(v);
     50         mPool.push(v);
     51     }
     52 
     53     /** Gets a view from the pool and prepares it */
     54     V pickUpViewFromPool(T preferredData, T prepareData) {
     55         V v = null;
     56         boolean isNewView = false;
     57         if (mPool.isEmpty()) {
     58             v = mViewCreator.createView(mContext);
     59             isNewView = true;
     60         } else {
     61             // Try and find a preferred view
     62             Iterator<V> iter = mPool.iterator();
     63             while (iter.hasNext()) {
     64                 V vpv = iter.next();
     65                 if (mViewCreator.hasPreferredData(vpv, preferredData)) {
     66                     v = vpv;
     67                     iter.remove();
     68                     break;
     69                 }
     70             }
     71             // Otherwise, just grab the first view
     72             if (v == null) {
     73                 v = mPool.pop();
     74             }
     75         }
     76         mViewCreator.onPickUpViewFromPool(v, prepareData, isNewView);
     77         return v;
     78     }
     79 
     80     /**
     81      * Returns the list of views in the pool.
     82      */
     83     List<V> getViews() {
     84         return mPool;
     85     }
     86 }
     87