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> {
createView(Context context)31         public V createView(Context context);
onReturnViewToPool(V v)32         public void onReturnViewToPool(V v);
onPickUpViewFromPool(V v, T prepareData, boolean isNewView)33         public void onPickUpViewFromPool(V v, T prepareData, boolean isNewView);
hasPreferredData(V v, T preferredData)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 */
ViewPool(Context context, ViewPoolConsumer<V, T> viewCreator)42     public ViewPool(Context context, ViewPoolConsumer<V, T> viewCreator) {
43         mContext = context;
44         mViewCreator = viewCreator;
45     }
46 
47     /** Returns a view into the pool */
returnViewToPool(V v)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 */
pickUpViewFromPool(T preferredData, T prepareData)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      */
getViews()83     List<V> getViews() {
84         return mPool;
85     }
86 }
87